xfs: remove XFS_BMAP_TRACE_EXLIST

[thirdparty/xfsprogs-dev.git] / libxfs / xfs_bmap.c

/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "libxfs_priv.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_dir2.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_trans.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_trans_space.h"
#include "xfs_trace.h"
#include "xfs_attr_leaf.h"
#include "xfs_quota_defs.h"
#include "xfs_rmap.h"
#include "xfs_ag_resv.h"
#include "xfs_refcount.h"


kmem_zone_t             *xfs_bmap_free_item_zone;

/*
 * Miscellaneous helper functions
 */

/*
 * Compute and fill in the value of the maximum depth of a bmap btree
 * in this filesystem.  Done once, during mount.
 */
void
xfs_bmap_compute_maxlevels(
        xfs_mount_t     *mp,            /* file system mount structure */
        int             whichfork)      /* data or attr fork */
{
        int             level;          /* btree level */
        uint            maxblocks;      /* max blocks at this level */
        uint            maxleafents;    /* max leaf entries possible */
        int             maxrootrecs;    /* max records in root block */
        int             minleafrecs;    /* min records in leaf block */
        int             minnoderecs;    /* min records in node block */
        int             sz;             /* root block size */

        /*
         * The maximum number of extents in a file, hence the maximum
         * number of leaf entries, is controlled by the type of di_nextents
         * (a signed 32-bit number, xfs_extnum_t), or by di_anextents
         * (a signed 16-bit number, xfs_aextnum_t).
         *
         * Note that we can no longer assume that if we are in ATTR1 that
         * the fork offset of all the inodes will be
         * (xfs_default_attroffset(ip) >> 3) because we could have mounted
         * with ATTR2 and then mounted back with ATTR1, keeping the
         * di_forkoff's fixed but probably at various positions. Therefore,
         * for both ATTR1 and ATTR2 we have to assume the worst case scenario
         * of a minimum size available.
         */
        if (whichfork == XFS_DATA_FORK) {
                maxleafents = MAXEXTNUM;
                sz = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
        } else {
                maxleafents = MAXAEXTNUM;
                sz = XFS_BMDR_SPACE_CALC(MINABTPTRS);
        }
        maxrootrecs = xfs_bmdr_maxrecs(sz, 0);
        minleafrecs = mp->m_bmap_dmnr[0];
        minnoderecs = mp->m_bmap_dmnr[1];
        maxblocks = (maxleafents + minleafrecs - 1) / minleafrecs;
        for (level = 1; maxblocks > 1; level++) {
                if (maxblocks <= maxrootrecs)
                        maxblocks = 1;
                else
                        maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs;
        }
        mp->m_bm_maxlevels[whichfork] = level;
}

STATIC int                              /* error */
xfs_bmbt_lookup_eq(
        struct xfs_btree_cur    *cur,
        struct xfs_bmbt_irec    *irec,
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.b = *irec;
        return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
}

STATIC int                              /* error */
xfs_bmbt_lookup_first(
        struct xfs_btree_cur    *cur,
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.b.br_startoff = 0;
        cur->bc_rec.b.br_startblock = 0;
        cur->bc_rec.b.br_blockcount = 0;
        return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
}

/*
 * Check if the inode needs to be converted to btree format.
 */
static inline bool xfs_bmap_needs_btree(struct xfs_inode *ip, int whichfork)
{
        return whichfork != XFS_COW_FORK &&
                XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS &&
                XFS_IFORK_NEXTENTS(ip, whichfork) >
                        XFS_IFORK_MAXEXT(ip, whichfork);
}

/*
 * Check if the inode should be converted to extent format.
 */
static inline bool xfs_bmap_wants_extents(struct xfs_inode *ip, int whichfork)
{
        return whichfork != XFS_COW_FORK &&
                XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE &&
                XFS_IFORK_NEXTENTS(ip, whichfork) <=
                        XFS_IFORK_MAXEXT(ip, whichfork);
}

/*
 * Update the record referred to by cur to the value given by irec
 * This either works (return 0) or gets an EFSCORRUPTED error.
 */
STATIC int
xfs_bmbt_update(
        struct xfs_btree_cur    *cur,
        struct xfs_bmbt_irec    *irec)
{
        union xfs_btree_rec     rec;

        xfs_bmbt_disk_set_all(&rec.bmbt, irec);
        return xfs_btree_update(cur, &rec);
}

/*
 * Compute the worst-case number of indirect blocks that will be used
 * for ip's delayed extent of length "len".
 */
STATIC xfs_filblks_t
xfs_bmap_worst_indlen(
        xfs_inode_t     *ip,            /* incore inode pointer */
        xfs_filblks_t   len)            /* delayed extent length */
{
        int             level;          /* btree level number */
        int             maxrecs;        /* maximum record count at this level */
        xfs_mount_t     *mp;            /* mount structure */
        xfs_filblks_t   rval;           /* return value */

        mp = ip->i_mount;
        maxrecs = mp->m_bmap_dmxr[0];
        for (level = 0, rval = 0;
             level < XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK);
             level++) {
                len += maxrecs - 1;
                do_div(len, maxrecs);
                rval += len;
                if (len == 1)
                        return rval + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) -
                                level - 1;
                if (level == 0)
                        maxrecs = mp->m_bmap_dmxr[1];
        }
        return rval;
}

/*
 * Calculate the default attribute fork offset for newly created inodes.
 */
uint
xfs_default_attroffset(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        uint                    offset;

        if (mp->m_sb.sb_inodesize == 256) {
                offset = XFS_LITINO(mp, ip->i_d.di_version) -
                                XFS_BMDR_SPACE_CALC(MINABTPTRS);
        } else {
                offset = XFS_BMDR_SPACE_CALC(6 * MINABTPTRS);
        }

        ASSERT(offset < XFS_LITINO(mp, ip->i_d.di_version));
        return offset;
}

/*
 * Helper routine to reset inode di_forkoff field when switching
 * attribute fork from local to extent format - we reset it where
 * possible to make space available for inline data fork extents.
 */
STATIC void
xfs_bmap_forkoff_reset(
        xfs_inode_t     *ip,
        int             whichfork)
{
        if (whichfork == XFS_ATTR_FORK &&
            ip->i_d.di_format != XFS_DINODE_FMT_DEV &&
            ip->i_d.di_format != XFS_DINODE_FMT_UUID &&
            ip->i_d.di_format != XFS_DINODE_FMT_BTREE) {
                uint    dfl_forkoff = xfs_default_attroffset(ip) >> 3;

                if (dfl_forkoff > ip->i_d.di_forkoff)
                        ip->i_d.di_forkoff = dfl_forkoff;
        }
}

#ifdef DEBUG
STATIC struct xfs_buf *
xfs_bmap_get_bp(
        struct xfs_btree_cur    *cur,
        xfs_fsblock_t           bno)
{
        struct xfs_log_item_desc *lidp;
        int                     i;

        if (!cur)
                return NULL;

        for (i = 0; i < XFS_BTREE_MAXLEVELS; i++) {
                if (!cur->bc_bufs[i])
                        break;
                if (XFS_BUF_ADDR(cur->bc_bufs[i]) == bno)
                        return cur->bc_bufs[i];
        }

        /* Chase down all the log items to see if the bp is there */
        list_for_each_entry(lidp, &cur->bc_tp->t_items, lid_trans) {
                struct xfs_buf_log_item *bip;
                bip = (struct xfs_buf_log_item *)lidp->lid_item;
                if (bip->bli_item.li_type == XFS_LI_BUF &&
                    XFS_BUF_ADDR(bip->bli_buf) == bno)
                        return bip->bli_buf;
        }

        return NULL;
}

STATIC void
xfs_check_block(
        struct xfs_btree_block  *block,
        xfs_mount_t             *mp,
        int                     root,
        short                   sz)
{
        int                     i, j, dmxr;
        __be64                  *pp, *thispa;   /* pointer to block address */
        xfs_bmbt_key_t          *prevp, *keyp;

        ASSERT(be16_to_cpu(block->bb_level) > 0);

        prevp = NULL;
        for( i = 1; i <= xfs_btree_get_numrecs(block); i++) {
                dmxr = mp->m_bmap_dmxr[0];
                keyp = XFS_BMBT_KEY_ADDR(mp, block, i);

                if (prevp) {
                        ASSERT(be64_to_cpu(prevp->br_startoff) <
                               be64_to_cpu(keyp->br_startoff));
                }
                prevp = keyp;

                /*
                 * Compare the block numbers to see if there are dups.
                 */
                if (root)
                        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, block, i, sz);
                else
                        pp = XFS_BMBT_PTR_ADDR(mp, block, i, dmxr);

                for (j = i+1; j <= be16_to_cpu(block->bb_numrecs); j++) {
                        if (root)
                                thispa = XFS_BMAP_BROOT_PTR_ADDR(mp, block, j, sz);
                        else
                                thispa = XFS_BMBT_PTR_ADDR(mp, block, j, dmxr);
                        if (*thispa == *pp) {
                                xfs_warn(mp, "%s: thispa(%d) == pp(%d) %Ld",
                                        __func__, j, i,
                                        (unsigned long long)be64_to_cpu(*thispa));
                                panic("%s: ptrs are equal in node\n",
                                        __func__);
                        }
                }
        }
}

/*
 * Check that the extents for the inode ip are in the right order in all
 * btree leaves. THis becomes prohibitively expensive for large extent count
 * files, so don't bother with inodes that have more than 10,000 extents in
 * them. The btree record ordering checks will still be done, so for such large
 * bmapbt constructs that is going to catch most corruptions.
 */
STATIC void
xfs_bmap_check_leaf_extents(
        xfs_btree_cur_t         *cur,   /* btree cursor or null */
        xfs_inode_t             *ip,            /* incore inode pointer */
        int                     whichfork)      /* data or attr fork */
{
        struct xfs_btree_block  *block; /* current btree block */
        xfs_fsblock_t           bno;    /* block # of "block" */
        xfs_buf_t               *bp;    /* buffer for "block" */
        int                     error;  /* error return value */
        xfs_extnum_t            i=0, j; /* index into the extents list */
        xfs_ifork_t             *ifp;   /* fork structure */
        int                     level;  /* btree level, for checking */
        xfs_mount_t             *mp;    /* file system mount structure */
        __be64                  *pp;    /* pointer to block address */
        xfs_bmbt_rec_t          *ep;    /* pointer to current extent */
        xfs_bmbt_rec_t          last = {0, 0}; /* last extent in prev block */
        xfs_bmbt_rec_t          *nextp; /* pointer to next extent */
        int                     bp_release = 0;

        if (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE) {
                return;
        }

        /* skip large extent count inodes */
        if (ip->i_d.di_nextents > 10000)
                return;

        bno = NULLFSBLOCK;
        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        block = ifp->if_broot;
        /*
         * Root level must use BMAP_BROOT_PTR_ADDR macro to get ptr out.
         */
        level = be16_to_cpu(block->bb_level);
        ASSERT(level > 0);
        xfs_check_block(block, mp, 1, ifp->if_broot_bytes);
        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, block, 1, ifp->if_broot_bytes);
        bno = be64_to_cpu(*pp);

        ASSERT(bno != NULLFSBLOCK);
        ASSERT(XFS_FSB_TO_AGNO(mp, bno) < mp->m_sb.sb_agcount);
        ASSERT(XFS_FSB_TO_AGBNO(mp, bno) < mp->m_sb.sb_agblocks);

        /*
         * Go down the tree until leaf level is reached, following the first
         * pointer (leftmost) at each level.
         */
        while (level-- > 0) {
                /* See if buf is in cur first */
                bp_release = 0;
                bp = xfs_bmap_get_bp(cur, XFS_FSB_TO_DADDR(mp, bno));
                if (!bp) {
                        bp_release = 1;
                        error = xfs_btree_read_bufl(mp, NULL, bno, 0, &bp,
                                                XFS_BMAP_BTREE_REF,
                                                &xfs_bmbt_buf_ops);
                        if (error)
                                goto error_norelse;
                }
                block = XFS_BUF_TO_BLOCK(bp);
                if (level == 0)
                        break;

                /*
                 * Check this block for basic sanity (increasing keys and
                 * no duplicate blocks).
                 */

                xfs_check_block(block, mp, 0, 0);
                pp = XFS_BMBT_PTR_ADDR(mp, block, 1, mp->m_bmap_dmxr[1]);
                bno = be64_to_cpu(*pp);
                XFS_WANT_CORRUPTED_GOTO(mp,
                                        XFS_FSB_SANITY_CHECK(mp, bno), error0);
                if (bp_release) {
                        bp_release = 0;
                        xfs_trans_brelse(NULL, bp);
                }
        }

        /*
         * Here with bp and block set to the leftmost leaf node in the tree.
         */
        i = 0;

        /*
         * Loop over all leaf nodes checking that all extents are in the right order.
         */
        for (;;) {
                xfs_fsblock_t   nextbno;
                xfs_extnum_t    num_recs;


                num_recs = xfs_btree_get_numrecs(block);

                /*
                 * Read-ahead the next leaf block, if any.
                 */

                nextbno = be64_to_cpu(block->bb_u.l.bb_rightsib);

                /*
                 * Check all the extents to make sure they are OK.
                 * If we had a previous block, the last entry should
                 * conform with the first entry in this one.
                 */

                ep = XFS_BMBT_REC_ADDR(mp, block, 1);
                if (i) {
                        ASSERT(xfs_bmbt_disk_get_startoff(&last) +
                               xfs_bmbt_disk_get_blockcount(&last) <=
                               xfs_bmbt_disk_get_startoff(ep));
                }
                for (j = 1; j < num_recs; j++) {
                        nextp = XFS_BMBT_REC_ADDR(mp, block, j + 1);
                        ASSERT(xfs_bmbt_disk_get_startoff(ep) +
                               xfs_bmbt_disk_get_blockcount(ep) <=
                               xfs_bmbt_disk_get_startoff(nextp));
                        ep = nextp;
                }

                last = *ep;
                i += num_recs;
                if (bp_release) {
                        bp_release = 0;
                        xfs_trans_brelse(NULL, bp);
                }
                bno = nextbno;
                /*
                 * If we've reached the end, stop.
                 */
                if (bno == NULLFSBLOCK)
                        break;

                bp_release = 0;
                bp = xfs_bmap_get_bp(cur, XFS_FSB_TO_DADDR(mp, bno));
                if (!bp) {
                        bp_release = 1;
                        error = xfs_btree_read_bufl(mp, NULL, bno, 0, &bp,
                                                XFS_BMAP_BTREE_REF,
                                                &xfs_bmbt_buf_ops);
                        if (error)
                                goto error_norelse;
                }
                block = XFS_BUF_TO_BLOCK(bp);
        }

        return;

error0:
        xfs_warn(mp, "%s: at error0", __func__);
        if (bp_release)
                xfs_trans_brelse(NULL, bp);
error_norelse:
        xfs_warn(mp, "%s: BAD after btree leaves for %d extents",
                __func__, i);
        panic("%s: CORRUPTED BTREE OR SOMETHING", __func__);
        return;
}

/*
 * Validate that the bmbt_irecs being returned from bmapi are valid
 * given the caller's original parameters.  Specifically check the
 * ranges of the returned irecs to ensure that they only extend beyond
 * the given parameters if the XFS_BMAPI_ENTIRE flag was set.
 */
STATIC void
xfs_bmap_validate_ret(
        xfs_fileoff_t           bno,
        xfs_filblks_t           len,
        int                     flags,
        xfs_bmbt_irec_t         *mval,
        int                     nmap,
        int                     ret_nmap)
{
        int                     i;              /* index to map values */

        ASSERT(ret_nmap <= nmap);

        for (i = 0; i < ret_nmap; i++) {
                ASSERT(mval[i].br_blockcount > 0);
                if (!(flags & XFS_BMAPI_ENTIRE)) {
                        ASSERT(mval[i].br_startoff >= bno);
                        ASSERT(mval[i].br_blockcount <= len);
                        ASSERT(mval[i].br_startoff + mval[i].br_blockcount <=
                               bno + len);
                } else {
                        ASSERT(mval[i].br_startoff < bno + len);
                        ASSERT(mval[i].br_startoff + mval[i].br_blockcount >
                               bno);
                }
                ASSERT(i == 0 ||
                       mval[i - 1].br_startoff + mval[i - 1].br_blockcount ==
                       mval[i].br_startoff);
                ASSERT(mval[i].br_startblock != DELAYSTARTBLOCK &&
                       mval[i].br_startblock != HOLESTARTBLOCK);
                ASSERT(mval[i].br_state == XFS_EXT_NORM ||
                       mval[i].br_state == XFS_EXT_UNWRITTEN);
        }
}

#else
#define xfs_bmap_check_leaf_extents(cur, ip, whichfork)         do { } while (0)
#define xfs_bmap_validate_ret(bno,len,flags,mval,onmap,nmap)    do { } while (0)
#endif /* DEBUG */

/*
 * bmap free list manipulation functions
 */

/*
 * Add the extent to the list of extents to be free at transaction end.
 * The list is maintained sorted (by block number).
 */
void
xfs_bmap_add_free(
        struct xfs_mount                *mp,
        struct xfs_defer_ops            *dfops,
        xfs_fsblock_t                   bno,
        xfs_filblks_t                   len,
        struct xfs_owner_info           *oinfo)
{
        struct xfs_extent_free_item     *new;           /* new element */
#ifdef DEBUG
        xfs_agnumber_t          agno;
        xfs_agblock_t           agbno;

        ASSERT(bno != NULLFSBLOCK);
        ASSERT(len > 0);
        ASSERT(len <= MAXEXTLEN);
        ASSERT(!isnullstartblock(bno));
        agno = XFS_FSB_TO_AGNO(mp, bno);
        agbno = XFS_FSB_TO_AGBNO(mp, bno);
        ASSERT(agno < mp->m_sb.sb_agcount);
        ASSERT(agbno < mp->m_sb.sb_agblocks);
        ASSERT(len < mp->m_sb.sb_agblocks);
        ASSERT(agbno + len <= mp->m_sb.sb_agblocks);
#endif
        ASSERT(xfs_bmap_free_item_zone != NULL);

        new = kmem_zone_alloc(xfs_bmap_free_item_zone, KM_SLEEP);
        new->xefi_startblock = bno;
        new->xefi_blockcount = (xfs_extlen_t)len;
        if (oinfo)
                new->xefi_oinfo = *oinfo;
        else
                xfs_rmap_skip_owner_update(&new->xefi_oinfo);
        trace_xfs_bmap_free_defer(mp, XFS_FSB_TO_AGNO(mp, bno), 0,
                        XFS_FSB_TO_AGBNO(mp, bno), len);
        xfs_defer_add(dfops, XFS_DEFER_OPS_TYPE_FREE, &new->xefi_list);
}

/*
 * Inode fork format manipulation functions
 */

/*
 * Transform a btree format file with only one leaf node, where the
 * extents list will fit in the inode, into an extents format file.
 * Since the file extents are already in-core, all we have to do is
 * give up the space for the btree root and pitch the leaf block.
 */
STATIC int                              /* error */
xfs_bmap_btree_to_extents(
        xfs_trans_t             *tp,    /* transaction pointer */
        xfs_inode_t             *ip,    /* incore inode pointer */
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     *logflagsp, /* inode logging flags */
        int                     whichfork)  /* data or attr fork */
{
        /* REFERENCED */
        struct xfs_btree_block  *cblock;/* child btree block */
        xfs_fsblock_t           cbno;   /* child block number */
        xfs_buf_t               *cbp;   /* child block's buffer */
        int                     error;  /* error return value */
        xfs_ifork_t             *ifp;   /* inode fork data */
        xfs_mount_t             *mp;    /* mount point structure */
        __be64                  *pp;    /* ptr to block address */
        struct xfs_btree_block  *rblock;/* root btree block */
        struct xfs_owner_info   oinfo;

        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(whichfork != XFS_COW_FORK);
        ASSERT(ifp->if_flags & XFS_IFEXTENTS);
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE);
        rblock = ifp->if_broot;
        ASSERT(be16_to_cpu(rblock->bb_level) == 1);
        ASSERT(be16_to_cpu(rblock->bb_numrecs) == 1);
        ASSERT(xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0) == 1);
        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, ifp->if_broot_bytes);
        cbno = be64_to_cpu(*pp);
        *logflagsp = 0;
#ifdef DEBUG
        XFS_WANT_CORRUPTED_RETURN(cur->bc_mp,
                        xfs_btree_check_lptr(cur, cbno, 1));
#endif
        error = xfs_btree_read_bufl(mp, tp, cbno, 0, &cbp, XFS_BMAP_BTREE_REF,
                                &xfs_bmbt_buf_ops);
        if (error)
                return error;
        cblock = XFS_BUF_TO_BLOCK(cbp);
        if ((error = xfs_btree_check_block(cur, cblock, 0, cbp)))
                return error;
        xfs_rmap_ino_bmbt_owner(&oinfo, ip->i_ino, whichfork);
        xfs_bmap_add_free(mp, cur->bc_private.b.dfops, cbno, 1, &oinfo);
        ip->i_d.di_nblocks--;
        xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, -1L);
        xfs_trans_binval(tp, cbp);
        if (cur->bc_bufs[0] == cbp)
                cur->bc_bufs[0] = NULL;
        xfs_iroot_realloc(ip, -1, whichfork);
        ASSERT(ifp->if_broot == NULL);
        ASSERT((ifp->if_flags & XFS_IFBROOT) == 0);
        XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
        *logflagsp = XFS_ILOG_CORE | xfs_ilog_fext(whichfork);
        return 0;
}

/*
 * Convert an extents-format file into a btree-format file.
 * The new file will have a root block (in the inode) and a single child block.
 */
STATIC int                                      /* error */
xfs_bmap_extents_to_btree(
        xfs_trans_t             *tp,            /* transaction pointer */
        xfs_inode_t             *ip,            /* incore inode pointer */
        xfs_fsblock_t           *firstblock,    /* first-block-allocated */
        struct xfs_defer_ops    *dfops,         /* blocks freed in xaction */
        xfs_btree_cur_t         **curp,         /* cursor returned to caller */
        int                     wasdel,         /* converting a delayed alloc */
        int                     *logflagsp,     /* inode logging flags */
        int                     whichfork)      /* data or attr fork */
{
        struct xfs_btree_block  *ablock;        /* allocated (child) bt block */
        xfs_buf_t               *abp;           /* buffer for ablock */
        xfs_alloc_arg_t         args;           /* allocation arguments */
        xfs_bmbt_rec_t          *arp;           /* child record pointer */
        struct xfs_btree_block  *block;         /* btree root block */
        xfs_btree_cur_t         *cur;           /* bmap btree cursor */
        xfs_bmbt_rec_host_t     *ep;            /* extent record pointer */
        int                     error;          /* error return value */
        xfs_extnum_t            i, cnt;         /* extent record index */
        xfs_ifork_t             *ifp;           /* inode fork pointer */
        xfs_bmbt_key_t          *kp;            /* root block key pointer */
        xfs_mount_t             *mp;            /* mount structure */
        xfs_extnum_t            nextents;       /* number of file extents */
        xfs_bmbt_ptr_t          *pp;            /* root block address pointer */

        mp = ip->i_mount;
        ASSERT(whichfork != XFS_COW_FORK);
        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS);

        /*
         * Make space in the inode incore.
         */
        xfs_iroot_realloc(ip, 1, whichfork);
        ifp->if_flags |= XFS_IFBROOT;

        /*
         * Fill in the root.
         */
        block = ifp->if_broot;
        xfs_btree_init_block_int(mp, block, XFS_BUF_DADDR_NULL,
                                 XFS_BTNUM_BMAP, 1, 1, ip->i_ino,
                                 XFS_BTREE_LONG_PTRS);
        /*
         * Need a cursor.  Can't allocate until bb_level is filled in.
         */
        cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
        cur->bc_private.b.firstblock = *firstblock;
        cur->bc_private.b.dfops = dfops;
        cur->bc_private.b.flags = wasdel ? XFS_BTCUR_BPRV_WASDEL : 0;
        /*
         * Convert to a btree with two levels, one record in root.
         */
        XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_BTREE);
        memset(&args, 0, sizeof(args));
        args.tp = tp;
        args.mp = mp;
        xfs_rmap_ino_bmbt_owner(&args.oinfo, ip->i_ino, whichfork);
        args.firstblock = *firstblock;
        if (*firstblock == NULLFSBLOCK) {
                args.type = XFS_ALLOCTYPE_START_BNO;
                args.fsbno = XFS_INO_TO_FSB(mp, ip->i_ino);
        } else if (dfops->dop_low) {
                args.type = XFS_ALLOCTYPE_START_BNO;
                args.fsbno = *firstblock;
        } else {
                args.type = XFS_ALLOCTYPE_NEAR_BNO;
                args.fsbno = *firstblock;
        }
        args.minlen = args.maxlen = args.prod = 1;
        args.wasdel = wasdel;
        *logflagsp = 0;
        if ((error = xfs_alloc_vextent(&args))) {
                xfs_iroot_realloc(ip, -1, whichfork);
                xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                return error;
        }

        if (WARN_ON_ONCE(args.fsbno == NULLFSBLOCK)) {
                xfs_iroot_realloc(ip, -1, whichfork);
                xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                return -ENOSPC;
        }
        /*
         * Allocation can't fail, the space was reserved.
         */
        ASSERT(*firstblock == NULLFSBLOCK ||
               args.agno >= XFS_FSB_TO_AGNO(mp, *firstblock));
        *firstblock = cur->bc_private.b.firstblock = args.fsbno;
        cur->bc_private.b.allocated++;
        ip->i_d.di_nblocks++;
        xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, 1L);
        abp = xfs_btree_get_bufl(mp, tp, args.fsbno, 0);
        /*
         * Fill in the child block.
         */
        abp->b_ops = &xfs_bmbt_buf_ops;
        ablock = XFS_BUF_TO_BLOCK(abp);
        xfs_btree_init_block_int(mp, ablock, abp->b_bn,
                                XFS_BTNUM_BMAP, 0, 0, ip->i_ino,
                                XFS_BTREE_LONG_PTRS);

        arp = XFS_BMBT_REC_ADDR(mp, ablock, 1);
        nextents =  xfs_iext_count(ifp);
        for (cnt = i = 0; i < nextents; i++) {
                ep = xfs_iext_get_ext(ifp, i);
                if (!isnullstartblock(xfs_bmbt_get_startblock(ep))) {
                        arp->l0 = cpu_to_be64(ep->l0);
                        arp->l1 = cpu_to_be64(ep->l1);
                        arp++; cnt++;
                }
        }
        ASSERT(cnt == XFS_IFORK_NEXTENTS(ip, whichfork));
        xfs_btree_set_numrecs(ablock, cnt);

        /*
         * Fill in the root key and pointer.
         */
        kp = XFS_BMBT_KEY_ADDR(mp, block, 1);
        arp = XFS_BMBT_REC_ADDR(mp, ablock, 1);
        kp->br_startoff = cpu_to_be64(xfs_bmbt_disk_get_startoff(arp));
        pp = XFS_BMBT_PTR_ADDR(mp, block, 1, xfs_bmbt_get_maxrecs(cur,
                                                be16_to_cpu(block->bb_level)));
        *pp = cpu_to_be64(args.fsbno);

        /*
         * Do all this logging at the end so that
         * the root is at the right level.
         */
        xfs_btree_log_block(cur, abp, XFS_BB_ALL_BITS);
        xfs_btree_log_recs(cur, abp, 1, be16_to_cpu(ablock->bb_numrecs));
        ASSERT(*curp == NULL);
        *curp = cur;
        *logflagsp = XFS_ILOG_CORE | xfs_ilog_fbroot(whichfork);
        return 0;
}

/*
 * Convert a local file to an extents file.
 * This code is out of bounds for data forks of regular files,
 * since the file data needs to get logged so things will stay consistent.
 * (The bmap-level manipulations are ok, though).
 */
void
xfs_bmap_local_to_extents_empty(
        struct xfs_inode        *ip,
        int                     whichfork)
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);

        ASSERT(whichfork != XFS_COW_FORK);
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL);
        ASSERT(ifp->if_bytes == 0);
        ASSERT(XFS_IFORK_NEXTENTS(ip, whichfork) == 0);

        xfs_bmap_forkoff_reset(ip, whichfork);
        ifp->if_flags &= ~XFS_IFINLINE;
        ifp->if_flags |= XFS_IFEXTENTS;
        XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
}


STATIC int                              /* error */
xfs_bmap_local_to_extents(
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_inode_t     *ip,            /* incore inode pointer */
        xfs_fsblock_t   *firstblock,    /* first block allocated in xaction */
        xfs_extlen_t    total,          /* total blocks needed by transaction */
        int             *logflagsp,     /* inode logging flags */
        int             whichfork,
        void            (*init_fn)(struct xfs_trans *tp,
                                   struct xfs_buf *bp,
                                   struct xfs_inode *ip,
                                   struct xfs_ifork *ifp))
{
        int             error = 0;
        int             flags;          /* logging flags returned */
        xfs_ifork_t     *ifp;           /* inode fork pointer */
        xfs_alloc_arg_t args;           /* allocation arguments */
        xfs_buf_t       *bp;            /* buffer for extent block */
        struct xfs_bmbt_irec rec;

        /*
         * We don't want to deal with the case of keeping inode data inline yet.
         * So sending the data fork of a regular inode is invalid.
         */
        ASSERT(!(S_ISREG(VFS_I(ip)->i_mode) && whichfork == XFS_DATA_FORK));
        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL);

        if (!ifp->if_bytes) {
                xfs_bmap_local_to_extents_empty(ip, whichfork);
                flags = XFS_ILOG_CORE;
                goto done;
        }

        flags = 0;
        error = 0;
        ASSERT((ifp->if_flags & (XFS_IFINLINE|XFS_IFEXTENTS|XFS_IFEXTIREC)) ==
                                                                XFS_IFINLINE);
        memset(&args, 0, sizeof(args));
        args.tp = tp;
        args.mp = ip->i_mount;
        xfs_rmap_ino_owner(&args.oinfo, ip->i_ino, whichfork, 0);
        args.firstblock = *firstblock;
        /*
         * Allocate a block.  We know we need only one, since the
         * file currently fits in an inode.
         */
        if (*firstblock == NULLFSBLOCK) {
                args.fsbno = XFS_INO_TO_FSB(args.mp, ip->i_ino);
                args.type = XFS_ALLOCTYPE_START_BNO;
        } else {
                args.fsbno = *firstblock;
                args.type = XFS_ALLOCTYPE_NEAR_BNO;
        }
        args.total = total;
        args.minlen = args.maxlen = args.prod = 1;
        error = xfs_alloc_vextent(&args);
        if (error)
                goto done;

        /* Can't fail, the space was reserved. */
        ASSERT(args.fsbno != NULLFSBLOCK);
        ASSERT(args.len == 1);
        *firstblock = args.fsbno;
        bp = xfs_btree_get_bufl(args.mp, tp, args.fsbno, 0);

        /*
         * Initialize the block, copy the data and log the remote buffer.
         *
         * The callout is responsible for logging because the remote format
         * might differ from the local format and thus we don't know how much to
         * log here. Note that init_fn must also set the buffer log item type
         * correctly.
         */
        init_fn(tp, bp, ip, ifp);

        /* account for the change in fork size */
        xfs_idata_realloc(ip, -ifp->if_bytes, whichfork);
        xfs_bmap_local_to_extents_empty(ip, whichfork);
        flags |= XFS_ILOG_CORE;

        rec.br_startoff = 0;
        rec.br_startblock = args.fsbno;
        rec.br_blockcount = 1;
        rec.br_state = XFS_EXT_NORM;
        xfs_iext_insert(ip, 0, 1, &rec, 0);

        XFS_IFORK_NEXT_SET(ip, whichfork, 1);
        ip->i_d.di_nblocks = 1;
        xfs_trans_mod_dquot_byino(tp, ip,
                XFS_TRANS_DQ_BCOUNT, 1L);
        flags |= xfs_ilog_fext(whichfork);

done:
        *logflagsp = flags;
        return error;
}

/*
 * Called from xfs_bmap_add_attrfork to handle btree format files.
 */
STATIC int                                      /* error */
xfs_bmap_add_attrfork_btree(
        xfs_trans_t             *tp,            /* transaction pointer */
        xfs_inode_t             *ip,            /* incore inode pointer */
        xfs_fsblock_t           *firstblock,    /* first block allocated */
        struct xfs_defer_ops    *dfops,         /* blocks to free at commit */
        int                     *flags)         /* inode logging flags */
{
        xfs_btree_cur_t         *cur;           /* btree cursor */
        int                     error;          /* error return value */
        xfs_mount_t             *mp;            /* file system mount struct */
        int                     stat;           /* newroot status */

        mp = ip->i_mount;
        if (ip->i_df.if_broot_bytes <= XFS_IFORK_DSIZE(ip))
                *flags |= XFS_ILOG_DBROOT;
        else {
                cur = xfs_bmbt_init_cursor(mp, tp, ip, XFS_DATA_FORK);
                cur->bc_private.b.dfops = dfops;
                cur->bc_private.b.firstblock = *firstblock;
                error = xfs_bmbt_lookup_first(cur, &stat);
                if (error)
                        goto error0;
                /* must be at least one entry */
                XFS_WANT_CORRUPTED_GOTO(mp, stat == 1, error0);
                if ((error = xfs_btree_new_iroot(cur, flags, &stat)))
                        goto error0;
                if (stat == 0) {
                        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
                        return -ENOSPC;
                }
                *firstblock = cur->bc_private.b.firstblock;
                cur->bc_private.b.allocated = 0;
                xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        }
        return 0;
error0:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Called from xfs_bmap_add_attrfork to handle extents format files.
 */
STATIC int                                      /* error */
xfs_bmap_add_attrfork_extents(
        xfs_trans_t             *tp,            /* transaction pointer */
        xfs_inode_t             *ip,            /* incore inode pointer */
        xfs_fsblock_t           *firstblock,    /* first block allocated */
        struct xfs_defer_ops    *dfops,         /* blocks to free at commit */
        int                     *flags)         /* inode logging flags */
{
        xfs_btree_cur_t         *cur;           /* bmap btree cursor */
        int                     error;          /* error return value */

        if (ip->i_d.di_nextents * sizeof(xfs_bmbt_rec_t) <= XFS_IFORK_DSIZE(ip))
                return 0;
        cur = NULL;
        error = xfs_bmap_extents_to_btree(tp, ip, firstblock, dfops, &cur, 0,
                flags, XFS_DATA_FORK);
        if (cur) {
                cur->bc_private.b.allocated = 0;
                xfs_btree_del_cursor(cur,
                        error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        }
        return error;
}

/*
 * Called from xfs_bmap_add_attrfork to handle local format files. Each
 * different data fork content type needs a different callout to do the
 * conversion. Some are basic and only require special block initialisation
 * callouts for the data formating, others (directories) are so specialised they
 * handle everything themselves.
 *
 * XXX (dgc): investigate whether directory conversion can use the generic
 * formatting callout. It should be possible - it's just a very complex
 * formatter.
 */
STATIC int                                      /* error */
xfs_bmap_add_attrfork_local(
        xfs_trans_t             *tp,            /* transaction pointer */
        xfs_inode_t             *ip,            /* incore inode pointer */
        xfs_fsblock_t           *firstblock,    /* first block allocated */
        struct xfs_defer_ops    *dfops,         /* blocks to free at commit */
        int                     *flags)         /* inode logging flags */
{
        xfs_da_args_t           dargs;          /* args for dir/attr code */

        if (ip->i_df.if_bytes <= XFS_IFORK_DSIZE(ip))
                return 0;

        if (S_ISDIR(VFS_I(ip)->i_mode)) {
                memset(&dargs, 0, sizeof(dargs));
                dargs.geo = ip->i_mount->m_dir_geo;
                dargs.dp = ip;
                dargs.firstblock = firstblock;
                dargs.dfops = dfops;
                dargs.total = dargs.geo->fsbcount;
                dargs.whichfork = XFS_DATA_FORK;
                dargs.trans = tp;
                return xfs_dir2_sf_to_block(&dargs);
        }

        if (S_ISLNK(VFS_I(ip)->i_mode))
                return xfs_bmap_local_to_extents(tp, ip, firstblock, 1,
                                                 flags, XFS_DATA_FORK,
                                                 xfs_symlink_local_to_remote);

        /* should only be called for types that support local format data */
        ASSERT(0);
        return -EFSCORRUPTED;
}

/*
 * Convert inode from non-attributed to attributed.
 * Must not be in a transaction, ip must not be locked.
 */
int                                             /* error code */
xfs_bmap_add_attrfork(
        xfs_inode_t             *ip,            /* incore inode pointer */
        int                     size,           /* space new attribute needs */
        int                     rsvd)           /* xact may use reserved blks */
{
        xfs_fsblock_t           firstblock;     /* 1st block/ag allocated */
        struct xfs_defer_ops    dfops;          /* freed extent records */
        xfs_mount_t             *mp;            /* mount structure */
        xfs_trans_t             *tp;            /* transaction pointer */
        int                     blks;           /* space reservation */
        int                     version = 1;    /* superblock attr version */
        int                     logflags;       /* logging flags */
        int                     error;          /* error return value */

        ASSERT(XFS_IFORK_Q(ip) == 0);

        mp = ip->i_mount;
        ASSERT(!XFS_NOT_DQATTACHED(mp, ip));

        blks = XFS_ADDAFORK_SPACE_RES(mp);

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_addafork, blks, 0,
                        rsvd ? XFS_TRANS_RESERVE : 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        error = xfs_trans_reserve_quota_nblks(tp, ip, blks, 0, rsvd ?
                        XFS_QMOPT_RES_REGBLKS | XFS_QMOPT_FORCE_RES :
                        XFS_QMOPT_RES_REGBLKS);
        if (error)
                goto trans_cancel;
        if (XFS_IFORK_Q(ip))
                goto trans_cancel;
        if (ip->i_d.di_anextents != 0) {
                error = -EFSCORRUPTED;
                goto trans_cancel;
        }
        if (ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS) {
                /*
                 * For inodes coming from pre-6.2 filesystems.
                 */
                ASSERT(ip->i_d.di_aformat == 0);
                ip->i_d.di_aformat = XFS_DINODE_FMT_EXTENTS;
        }

        xfs_trans_ijoin(tp, ip, 0);
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        switch (ip->i_d.di_format) {
        case XFS_DINODE_FMT_DEV:
                ip->i_d.di_forkoff = roundup(sizeof(xfs_dev_t), 8) >> 3;
                break;
        case XFS_DINODE_FMT_UUID:
                ip->i_d.di_forkoff = roundup(sizeof(uuid_t), 8) >> 3;
                break;
        case XFS_DINODE_FMT_LOCAL:
        case XFS_DINODE_FMT_EXTENTS:
        case XFS_DINODE_FMT_BTREE:
                ip->i_d.di_forkoff = xfs_attr_shortform_bytesfit(ip, size);
                if (!ip->i_d.di_forkoff)
                        ip->i_d.di_forkoff = xfs_default_attroffset(ip) >> 3;
                else if (mp->m_flags & XFS_MOUNT_ATTR2)
                        version = 2;
                break;
        default:
                ASSERT(0);
                error = -EINVAL;
                goto trans_cancel;
        }

        ASSERT(ip->i_afp == NULL);
        ip->i_afp = kmem_zone_zalloc(xfs_ifork_zone, KM_SLEEP);
        ip->i_afp->if_flags = XFS_IFEXTENTS;
        logflags = 0;
        xfs_defer_init(&dfops, &firstblock);
        switch (ip->i_d.di_format) {
        case XFS_DINODE_FMT_LOCAL:
                error = xfs_bmap_add_attrfork_local(tp, ip, &firstblock, &dfops,
                        &logflags);
                break;
        case XFS_DINODE_FMT_EXTENTS:
                error = xfs_bmap_add_attrfork_extents(tp, ip, &firstblock,
                        &dfops, &logflags);
                break;
        case XFS_DINODE_FMT_BTREE:
                error = xfs_bmap_add_attrfork_btree(tp, ip, &firstblock, &dfops,
                        &logflags);
                break;
        default:
                error = 0;
                break;
        }
        if (logflags)
                xfs_trans_log_inode(tp, ip, logflags);
        if (error)
                goto bmap_cancel;
        if (!xfs_sb_version_hasattr(&mp->m_sb) ||
           (!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2)) {
                bool log_sb = false;

                spin_lock(&mp->m_sb_lock);
                if (!xfs_sb_version_hasattr(&mp->m_sb)) {
                        xfs_sb_version_addattr(&mp->m_sb);
                        log_sb = true;
                }
                if (!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2) {
                        xfs_sb_version_addattr2(&mp->m_sb);
                        log_sb = true;
                }
                spin_unlock(&mp->m_sb_lock);
                if (log_sb)
                        xfs_log_sb(tp);
        }

        error = xfs_defer_finish(&tp, &dfops);
        if (error)
                goto bmap_cancel;
        error = xfs_trans_commit(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;

bmap_cancel:
        xfs_defer_cancel(&dfops);
trans_cancel:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * Internal and external extent tree search functions.
 */

/*
 * Read in the extents to if_extents.
 * All inode fields are set up by caller, we just traverse the btree
 * and copy the records in. If the file system cannot contain unwritten
 * extents, the records are checked for no "state" flags.
 */
int                                     /* error */
xfs_bmap_read_extents(
        xfs_trans_t             *tp,    /* transaction pointer */
        xfs_inode_t             *ip,    /* incore inode */
        int                     whichfork) /* data or attr fork */
{
        struct xfs_btree_block  *block; /* current btree block */
        xfs_fsblock_t           bno;    /* block # of "block" */
        xfs_buf_t               *bp;    /* buffer for "block" */
        int                     error;  /* error return value */
        xfs_extnum_t            i, j;   /* index into the extents list */
        xfs_ifork_t             *ifp;   /* fork structure */
        int                     level;  /* btree level, for checking */
        xfs_mount_t             *mp;    /* file system mount structure */
        __be64                  *pp;    /* pointer to block address */
        /* REFERENCED */
        xfs_extnum_t            room;   /* number of entries there's room for */
        int                     state = xfs_bmap_fork_to_state(whichfork);

        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        block = ifp->if_broot;
        /*
         * Root level must use BMAP_BROOT_PTR_ADDR macro to get ptr out.
         */
        level = be16_to_cpu(block->bb_level);
        ASSERT(level > 0);
        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, block, 1, ifp->if_broot_bytes);
        bno = be64_to_cpu(*pp);

        /*
         * Go down the tree until leaf level is reached, following the first
         * pointer (leftmost) at each level.
         */
        while (level-- > 0) {
                error = xfs_btree_read_bufl(mp, tp, bno, 0, &bp,
                                XFS_BMAP_BTREE_REF, &xfs_bmbt_buf_ops);
                if (error)
                        return error;
                block = XFS_BUF_TO_BLOCK(bp);
                if (level == 0)
                        break;
                pp = XFS_BMBT_PTR_ADDR(mp, block, 1, mp->m_bmap_dmxr[1]);
                bno = be64_to_cpu(*pp);
                XFS_WANT_CORRUPTED_GOTO(mp,
                        XFS_FSB_SANITY_CHECK(mp, bno), error0);
                xfs_trans_brelse(tp, bp);
        }
        /*
         * Here with bp and block set to the leftmost leaf node in the tree.
         */
        room = xfs_iext_count(ifp);
        i = 0;
        /*
         * Loop over all leaf nodes.  Copy information to the extent records.
         */
        for (;;) {
                xfs_bmbt_rec_t  *frp;
                xfs_fsblock_t   nextbno;
                xfs_extnum_t    num_recs;

                num_recs = xfs_btree_get_numrecs(block);
                if (unlikely(i + num_recs > room)) {
                        ASSERT(i + num_recs <= room);
                        xfs_warn(ip->i_mount,
                                "corrupt dinode %Lu, (btree extents).",
                                (unsigned long long) ip->i_ino);
                        XFS_CORRUPTION_ERROR("xfs_bmap_read_extents(1)",
                                XFS_ERRLEVEL_LOW, ip->i_mount, block);
                        goto error0;
                }
                /*
                 * Read-ahead the next leaf block, if any.
                 */
                nextbno = be64_to_cpu(block->bb_u.l.bb_rightsib);
                if (nextbno != NULLFSBLOCK)
                        xfs_btree_reada_bufl(mp, nextbno, 1,
                                             &xfs_bmbt_buf_ops);
                /*
                 * Copy records into the extent records.
                 */
                frp = XFS_BMBT_REC_ADDR(mp, block, 1);
                for (j = 0; j < num_recs; j++, i++, frp++) {
                        xfs_bmbt_rec_host_t *trp = xfs_iext_get_ext(ifp, i);
                        trp->l0 = be64_to_cpu(frp->l0);
                        trp->l1 = be64_to_cpu(frp->l1);
                        if (!xfs_bmbt_validate_extent(mp, whichfork, trp)) {
                                XFS_ERROR_REPORT("xfs_bmap_read_extents(2)",
                                                 XFS_ERRLEVEL_LOW, mp);
                                goto error0;
                        }
                        trace_xfs_read_extent(ip, i, state, _THIS_IP_);
                }
                xfs_trans_brelse(tp, bp);
                bno = nextbno;
                /*
                 * If we've reached the end, stop.
                 */
                if (bno == NULLFSBLOCK)
                        break;
                error = xfs_btree_read_bufl(mp, tp, bno, 0, &bp,
                                XFS_BMAP_BTREE_REF, &xfs_bmbt_buf_ops);
                if (error)
                        return error;
                block = XFS_BUF_TO_BLOCK(bp);
        }
        if (i != XFS_IFORK_NEXTENTS(ip, whichfork))
                return -EFSCORRUPTED;
        ASSERT(i == xfs_iext_count(ifp));
        return 0;
error0:
        xfs_trans_brelse(tp, bp);
        return -EFSCORRUPTED;
}

/*
 * Returns the file-relative block number of the first unused block(s)
 * in the file with at least "len" logically contiguous blocks free.
 * This is the lowest-address hole if the file has holes, else the first block
 * past the end of file.
 * Return 0 if the file is currently local (in-inode).
 */
int                                             /* error */
xfs_bmap_first_unused(
        xfs_trans_t     *tp,                    /* transaction pointer */
        xfs_inode_t     *ip,                    /* incore inode */
        xfs_extlen_t    len,                    /* size of hole to find */
        xfs_fileoff_t   *first_unused,          /* unused block */
        int             whichfork)              /* data or attr fork */
{
        int             error;                  /* error return value */
        int             idx;                    /* extent record index */
        xfs_ifork_t     *ifp;                   /* inode fork pointer */
        xfs_fileoff_t   lastaddr;               /* last block number seen */
        xfs_fileoff_t   lowest;                 /* lowest useful block */
        xfs_fileoff_t   max;                    /* starting useful block */
        xfs_extnum_t    nextents;               /* number of extent entries */

        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE ||
               XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS ||
               XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL);
        if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL) {
                *first_unused = 0;
                return 0;
        }
        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (!(ifp->if_flags & XFS_IFEXTENTS) &&
            (error = xfs_iread_extents(tp, ip, whichfork)))
                return error;
        lowest = *first_unused;
        nextents = xfs_iext_count(ifp);
        for (idx = 0, lastaddr = 0, max = lowest; idx < nextents; idx++) {
                struct xfs_bmbt_irec got;

                xfs_iext_get_extent(ifp, idx, &got);

                /*
                 * See if the hole before this extent will work.
                 */
                if (got.br_startoff >= lowest + len &&
                    got.br_startoff - max >= len) {
                        *first_unused = max;
                        return 0;
                }
                lastaddr = got.br_startoff + got.br_blockcount;
                max = XFS_FILEOFF_MAX(lastaddr, lowest);
        }
        *first_unused = max;
        return 0;
}

/*
 * Returns the file-relative block number of the last block - 1 before
 * last_block (input value) in the file.
 * This is not based on i_size, it is based on the extent records.
 * Returns 0 for local files, as they do not have extent records.
 */
int                                             /* error */
xfs_bmap_last_before(
        struct xfs_trans        *tp,            /* transaction pointer */
        struct xfs_inode        *ip,            /* incore inode */
        xfs_fileoff_t           *last_block,    /* last block */
        int                     whichfork)      /* data or attr fork */
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_bmbt_irec    got;
        xfs_extnum_t            idx;
        int                     error;

        switch (XFS_IFORK_FORMAT(ip, whichfork)) {
        case XFS_DINODE_FMT_LOCAL:
                *last_block = 0;
                return 0;
        case XFS_DINODE_FMT_BTREE:
        case XFS_DINODE_FMT_EXTENTS:
                break;
        default:
                return -EIO;
        }

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(tp, ip, whichfork);
                if (error)
                        return error;
        }

        if (xfs_iext_lookup_extent(ip, ifp, *last_block - 1, &idx, &got)) {
                if (got.br_startoff <= *last_block - 1)
                        return 0;
        }

        if (xfs_iext_get_extent(ifp, idx - 1, &got)) {
                *last_block = got.br_startoff + got.br_blockcount;
                return 0;
        }

        *last_block = 0;
        return 0;
}

int
xfs_bmap_last_extent(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        int                     whichfork,
        struct xfs_bmbt_irec    *rec,
        int                     *is_empty)
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        int                     error;
        int                     nextents;

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(tp, ip, whichfork);
                if (error)
                        return error;
        }

        nextents = xfs_iext_count(ifp);
        if (nextents == 0) {
                *is_empty = 1;
                return 0;
        }

        xfs_iext_get_extent(ifp, nextents - 1, rec);
        *is_empty = 0;
        return 0;
}

/*
 * Check the last inode extent to determine whether this allocation will result
 * in blocks being allocated at the end of the file. When we allocate new data
 * blocks at the end of the file which do not start at the previous data block,
 * we will try to align the new blocks at stripe unit boundaries.
 *
 * Returns 1 in bma->aeof if the file (fork) is empty as any new write will be
 * at, or past the EOF.
 */
STATIC int
xfs_bmap_isaeof(
        struct xfs_bmalloca     *bma,
        int                     whichfork)
{
        struct xfs_bmbt_irec    rec;
        int                     is_empty;
        int                     error;

        bma->aeof = false;
        error = xfs_bmap_last_extent(NULL, bma->ip, whichfork, &rec,
                                     &is_empty);
        if (error)
                return error;

        if (is_empty) {
                bma->aeof = true;
                return 0;
        }

        /*
         * Check if we are allocation or past the last extent, or at least into
         * the last delayed allocated extent.
         */
        bma->aeof = bma->offset >= rec.br_startoff + rec.br_blockcount ||
                (bma->offset >= rec.br_startoff &&
                 isnullstartblock(rec.br_startblock));
        return 0;
}

/*
 * Returns the file-relative block number of the first block past eof in
 * the file.  This is not based on i_size, it is based on the extent records.
 * Returns 0 for local files, as they do not have extent records.
 */
int
xfs_bmap_last_offset(
        struct xfs_inode        *ip,
        xfs_fileoff_t           *last_block,
        int                     whichfork)
{
        struct xfs_bmbt_irec    rec;
        int                     is_empty;
        int                     error;

        *last_block = 0;

        if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL)
                return 0;

        if (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE &&
            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS)
               return -EIO;

        error = xfs_bmap_last_extent(NULL, ip, whichfork, &rec, &is_empty);
        if (error || is_empty)
                return error;

        *last_block = rec.br_startoff + rec.br_blockcount;
        return 0;
}

/*
 * Returns whether the selected fork of the inode has exactly one
 * block or not.  For the data fork we check this matches di_size,
 * implying the file's range is 0..bsize-1.
 */
int                                     /* 1=>1 block, 0=>otherwise */
xfs_bmap_one_block(
        xfs_inode_t     *ip,            /* incore inode */
        int             whichfork)      /* data or attr fork */
{
        xfs_ifork_t     *ifp;           /* inode fork pointer */
        int             rval;           /* return value */
        xfs_bmbt_irec_t s;              /* internal version of extent */

#ifndef DEBUG
        if (whichfork == XFS_DATA_FORK)
                return XFS_ISIZE(ip) == ip->i_mount->m_sb.sb_blocksize;
#endif  /* !DEBUG */
        if (XFS_IFORK_NEXTENTS(ip, whichfork) != 1)
                return 0;
        if (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS)
                return 0;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(ifp->if_flags & XFS_IFEXTENTS);
        xfs_iext_get_extent(ifp, 0, &s);
        rval = s.br_startoff == 0 && s.br_blockcount == 1;
        if (rval && whichfork == XFS_DATA_FORK)
                ASSERT(XFS_ISIZE(ip) == ip->i_mount->m_sb.sb_blocksize);
        return rval;
}

/*
 * Extent tree manipulation functions used during allocation.
 */

/*
 * Convert a delayed allocation to a real allocation.
 */
STATIC int                              /* error */
xfs_bmap_add_extent_delay_real(
        struct xfs_bmalloca     *bma,
        int                     whichfork)
{
        struct xfs_bmbt_irec    *new = &bma->got;
        int                     error;  /* error return value */
        int                     i;      /* temp state */
        xfs_ifork_t             *ifp;   /* inode fork pointer */
        xfs_fileoff_t           new_endoff;     /* end offset of new entry */
        xfs_bmbt_irec_t         r[3];   /* neighbor extent entries */
                                        /* left is 0, right is 1, prev is 2 */
        int                     rval=0; /* return value (logging flags) */
        int                     state = xfs_bmap_fork_to_state(whichfork);
        xfs_filblks_t           da_new; /* new count del alloc blocks used */
        xfs_filblks_t           da_old; /* old count del alloc blocks used */
        xfs_filblks_t           temp=0; /* value for da_new calculations */
        int                     tmp_rval;       /* partial logging flags */
        struct xfs_mount        *mp;
        xfs_extnum_t            *nextents;
        struct xfs_bmbt_irec    old;

        mp = bma->ip->i_mount;
        ifp = XFS_IFORK_PTR(bma->ip, whichfork);
        ASSERT(whichfork != XFS_ATTR_FORK);
        nextents = (whichfork == XFS_COW_FORK ? &bma->ip->i_cnextents :
                                                &bma->ip->i_d.di_nextents);

        ASSERT(bma->idx >= 0);
        ASSERT(bma->idx <= xfs_iext_count(ifp));
        ASSERT(!isnullstartblock(new->br_startblock));
        ASSERT(!bma->cur ||
               (bma->cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL));

        XFS_STATS_INC(mp, xs_add_exlist);

#define LEFT            r[0]
#define RIGHT           r[1]
#define PREV            r[2]

        /*
         * Set up a bunch of variables to make the tests simpler.
         */
        xfs_iext_get_extent(ifp, bma->idx, &PREV);
        new_endoff = new->br_startoff + new->br_blockcount;
        ASSERT(isnullstartblock(PREV.br_startblock));
        ASSERT(PREV.br_startoff <= new->br_startoff);
        ASSERT(PREV.br_startoff + PREV.br_blockcount >= new_endoff);

        da_old = startblockval(PREV.br_startblock);
        da_new = 0;

        /*
         * Set flags determining what part of the previous delayed allocation
         * extent is being replaced by a real allocation.
         */
        if (PREV.br_startoff == new->br_startoff)
                state |= BMAP_LEFT_FILLING;
        if (PREV.br_startoff + PREV.br_blockcount == new_endoff)
                state |= BMAP_RIGHT_FILLING;

        /*
         * Check and set flags if this segment has a left neighbor.
         * Don't set contiguous if the combined extent would be too large.
         */
        if (bma->idx > 0) {
                state |= BMAP_LEFT_VALID;
                xfs_iext_get_extent(ifp, bma->idx - 1, &LEFT);

                if (isnullstartblock(LEFT.br_startblock))
                        state |= BMAP_LEFT_DELAY;
        }

        if ((state & BMAP_LEFT_VALID) && !(state & BMAP_LEFT_DELAY) &&
            LEFT.br_startoff + LEFT.br_blockcount == new->br_startoff &&
            LEFT.br_startblock + LEFT.br_blockcount == new->br_startblock &&
            LEFT.br_state == new->br_state &&
            LEFT.br_blockcount + new->br_blockcount <= MAXEXTLEN)
                state |= BMAP_LEFT_CONTIG;

        /*
         * Check and set flags if this segment has a right neighbor.
         * Don't set contiguous if the combined extent would be too large.
         * Also check for all-three-contiguous being too large.
         */
        if (bma->idx < xfs_iext_count(ifp) - 1) {
                state |= BMAP_RIGHT_VALID;
                xfs_iext_get_extent(ifp, bma->idx + 1, &RIGHT);

                if (isnullstartblock(RIGHT.br_startblock))
                        state |= BMAP_RIGHT_DELAY;
        }

        if ((state & BMAP_RIGHT_VALID) && !(state & BMAP_RIGHT_DELAY) &&
            new_endoff == RIGHT.br_startoff &&
            new->br_startblock + new->br_blockcount == RIGHT.br_startblock &&
            new->br_state == RIGHT.br_state &&
            new->br_blockcount + RIGHT.br_blockcount <= MAXEXTLEN &&
            ((state & (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
                       BMAP_RIGHT_FILLING)) !=
                      (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
                       BMAP_RIGHT_FILLING) ||
             LEFT.br_blockcount + new->br_blockcount + RIGHT.br_blockcount
                        <= MAXEXTLEN))
                state |= BMAP_RIGHT_CONTIG;

        error = 0;
        /*
         * Switch out based on the FILLING and CONTIG state bits.
         */
        switch (state & (BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG |
                         BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG)) {
        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG |
             BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Filling in all of a previously delayed allocation extent.
                 * The left and right neighbors are both contiguous with new.
                 */
                bma->idx--;
                LEFT.br_blockcount += PREV.br_blockcount + RIGHT.br_blockcount;
                xfs_iext_update_extent(bma->ip, state, bma->idx, &LEFT);

                xfs_iext_remove(bma->ip, bma->idx + 1, 2, state);
                (*nextents)--;
                if (bma->cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(bma->cur, &RIGHT, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_btree_delete(bma->cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_btree_decrement(bma->cur, 0, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(bma->cur, &LEFT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG:
                /*
                 * Filling in all of a previously delayed allocation extent.
                 * The left neighbor is contiguous, the right is not.
                 */
                bma->idx--;

                old = LEFT;
                LEFT.br_blockcount += PREV.br_blockcount;
                xfs_iext_update_extent(bma->ip, state, bma->idx, &LEFT);

                xfs_iext_remove(bma->ip, bma->idx + 1, 1, state);
                if (bma->cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(bma->cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(bma->cur, &LEFT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Filling in all of a previously delayed allocation extent.
                 * The right neighbor is contiguous, the left is not.
                 */
                PREV.br_startblock = new->br_startblock;
                PREV.br_blockcount += RIGHT.br_blockcount;
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                xfs_iext_remove(bma->ip, bma->idx + 1, 1, state);
                if (bma->cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(bma->cur, &RIGHT, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(bma->cur, &PREV);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING:
                /*
                 * Filling in all of a previously delayed allocation extent.
                 * Neither the left nor right neighbors are contiguous with
                 * the new one.
                 */
                PREV.br_startblock = new->br_startblock;
                PREV.br_state = new->br_state;
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                (*nextents)++;
                if (bma->cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(bma->cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        error = xfs_btree_insert(bma->cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG:
                /*
                 * Filling in the first part of a previous delayed allocation.
                 * The left neighbor is contiguous.
                 */
                old = LEFT;
                temp = PREV.br_blockcount - new->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(bma->ip, temp),
                                startblockval(PREV.br_startblock));

                LEFT.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(bma->ip, state, bma->idx - 1, &LEFT);

                PREV.br_blockcount = temp = PREV.br_blockcount - new->br_blockcount;
                PREV.br_startoff += new->br_blockcount;
                PREV.br_startblock = nullstartblock(da_new);
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                if (bma->cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(bma->cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(bma->cur, &LEFT);
                        if (error)
                                goto done;
                }

                bma->idx--;
                break;

        case BMAP_LEFT_FILLING:
                /*
                 * Filling in the first part of a previous delayed allocation.
                 * The left neighbor is not contiguous.
                 */
                xfs_iext_insert(bma->ip, bma->idx, 1, new, state);
                (*nextents)++;
                if (bma->cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(bma->cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        error = xfs_btree_insert(bma->cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }

                if (xfs_bmap_needs_btree(bma->ip, whichfork)) {
                        error = xfs_bmap_extents_to_btree(bma->tp, bma->ip,
                                        bma->firstblock, bma->dfops,
                                        &bma->cur, 1, &tmp_rval, whichfork);
                        rval |= tmp_rval;
                        if (error)
                                goto done;
                }

                temp = PREV.br_blockcount - new->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(bma->ip, temp),
                        startblockval(PREV.br_startblock) -
                        (bma->cur ? bma->cur->bc_private.b.allocated : 0));

                PREV.br_startoff = new_endoff;
                PREV.br_blockcount = temp;
                PREV.br_startblock = nullstartblock(da_new);
                xfs_iext_update_extent(bma->ip, state, bma->idx + 1, &PREV);
                break;

        case BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Filling in the last part of a previous delayed allocation.
                 * The right neighbor is contiguous with the new allocation.
                 */
                old = RIGHT;
                RIGHT.br_startoff = new->br_startoff;
                RIGHT.br_startblock = new->br_startblock;
                RIGHT.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(bma->ip, state, bma->idx + 1, &RIGHT);

                if (bma->cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(bma->cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(bma->cur, &RIGHT);
                        if (error)
                                goto done;
                }

                temp = PREV.br_blockcount - new->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(bma->ip, temp),
                        startblockval(PREV.br_startblock));

                PREV.br_blockcount = temp;
                PREV.br_startblock = nullstartblock(da_new);
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                bma->idx++;
                break;

        case BMAP_RIGHT_FILLING:
                /*
                 * Filling in the last part of a previous delayed allocation.
                 * The right neighbor is not contiguous.
                 */
                xfs_iext_insert(bma->ip, bma->idx + 1, 1, new, state);
                (*nextents)++;
                if (bma->cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(bma->cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        error = xfs_btree_insert(bma->cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }

                if (xfs_bmap_needs_btree(bma->ip, whichfork)) {
                        error = xfs_bmap_extents_to_btree(bma->tp, bma->ip,
                                bma->firstblock, bma->dfops, &bma->cur, 1,
                                &tmp_rval, whichfork);
                        rval |= tmp_rval;
                        if (error)
                                goto done;
                }

                temp = PREV.br_blockcount - new->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(bma->ip, temp),
                        startblockval(PREV.br_startblock) -
                        (bma->cur ? bma->cur->bc_private.b.allocated : 0));

                PREV.br_startblock = nullstartblock(da_new);
                PREV.br_blockcount = temp;
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                bma->idx++;
                break;

        case 0:
                /*
                 * Filling in the middle part of a previous delayed allocation.
                 * Contiguity is impossible here.
                 * This case is avoided almost all the time.
                 *
                 * We start with a delayed allocation:
                 *
                 * +ddddddddddddddddddddddddddddddddddddddddddddddddddddddd+
                 *  PREV @ idx
                 *
                 * and we are allocating:
                 *                     +rrrrrrrrrrrrrrrrr+
                 *                            new
                 *
                 * and we set it up for insertion as:
                 * +ddddddddddddddddddd+rrrrrrrrrrrrrrrrr+ddddddddddddddddd+
                 *                            new
                 *  PREV @ idx          LEFT              RIGHT
                 *                      inserted at idx + 1
                 */
                old = PREV;

                /* LEFT is the new middle */
                LEFT = *new;

                /* RIGHT is the new right */
                RIGHT.br_state = PREV.br_state;
                RIGHT.br_startoff = new_endoff;
                RIGHT.br_blockcount =
                        PREV.br_startoff + PREV.br_blockcount - new_endoff;
                RIGHT.br_startblock =
                        nullstartblock(xfs_bmap_worst_indlen(bma->ip,
                                        RIGHT.br_blockcount));

                /* truncate PREV */
                PREV.br_blockcount = new->br_startoff - PREV.br_startoff;
                PREV.br_startblock =
                        nullstartblock(xfs_bmap_worst_indlen(bma->ip,
                                        PREV.br_blockcount));
                xfs_iext_update_extent(bma->ip, state, bma->idx, &PREV);

                /* insert LEFT (r[0]) and RIGHT (r[1]) at the same time */
                xfs_iext_insert(bma->ip, bma->idx + 1, 2, &LEFT, state);
                (*nextents)++;

                if (bma->cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(bma->cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        error = xfs_btree_insert(bma->cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }

                if (xfs_bmap_needs_btree(bma->ip, whichfork)) {
                        error = xfs_bmap_extents_to_btree(bma->tp, bma->ip,
                                        bma->firstblock, bma->dfops, &bma->cur,
                                        1, &tmp_rval, whichfork);
                        rval |= tmp_rval;
                        if (error)
                                goto done;
                }

                da_new = startblockval(PREV.br_startblock) +
                         startblockval(RIGHT.br_startblock);
                bma->idx++;
                break;

        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_LEFT_FILLING | BMAP_RIGHT_CONTIG:
        case BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG:
        case BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_LEFT_CONTIG:
        case BMAP_RIGHT_CONTIG:
                /*
                 * These cases are all impossible.
                 */
                ASSERT(0);
        }

        /* add reverse mapping */
        error = xfs_rmap_map_extent(mp, bma->dfops, bma->ip, whichfork, new);
        if (error)
                goto done;

        /* convert to a btree if necessary */
        if (xfs_bmap_needs_btree(bma->ip, whichfork)) {
                int     tmp_logflags;   /* partial log flag return val */

                ASSERT(bma->cur == NULL);
                error = xfs_bmap_extents_to_btree(bma->tp, bma->ip,
                                bma->firstblock, bma->dfops, &bma->cur,
                                da_old > 0, &tmp_logflags, whichfork);
                bma->logflags |= tmp_logflags;
                if (error)
                        goto done;
        }

        if (bma->cur) {
                da_new += bma->cur->bc_private.b.allocated;
                bma->cur->bc_private.b.allocated = 0;
        }

        /* adjust for changes in reserved delayed indirect blocks */
        if (da_new != da_old) {
                ASSERT(state == 0 || da_new < da_old);
                error = xfs_mod_fdblocks(mp, (int64_t)(da_old - da_new),
                                false);
        }

        xfs_bmap_check_leaf_extents(bma->cur, bma->ip, whichfork);
done:
        if (whichfork != XFS_COW_FORK)
                bma->logflags |= rval;
        return error;
#undef  LEFT
#undef  RIGHT
#undef  PREV
}

/*
 * Convert an unwritten allocation to a real allocation or vice versa.
 */
STATIC int                              /* error */
xfs_bmap_add_extent_unwritten_real(
        struct xfs_trans        *tp,
        xfs_inode_t             *ip,    /* incore inode pointer */
        int                     whichfork,
        xfs_extnum_t            *idx,   /* extent number to update/insert */
        xfs_btree_cur_t         **curp, /* if *curp is null, not a btree */
        xfs_bmbt_irec_t         *new,   /* new data to add to file extents */
        xfs_fsblock_t           *first, /* pointer to firstblock variable */
        struct xfs_defer_ops    *dfops, /* list of extents to be freed */
        int                     *logflagsp) /* inode logging flags */
{
        xfs_btree_cur_t         *cur;   /* btree cursor */
        int                     error;  /* error return value */
        int                     i;      /* temp state */
        xfs_ifork_t             *ifp;   /* inode fork pointer */
        xfs_fileoff_t           new_endoff;     /* end offset of new entry */
        xfs_bmbt_irec_t         r[3];   /* neighbor extent entries */
                                        /* left is 0, right is 1, prev is 2 */
        int                     rval=0; /* return value (logging flags) */
        int                     state = xfs_bmap_fork_to_state(whichfork);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_bmbt_irec    old;

        *logflagsp = 0;

        cur = *curp;
        ifp = XFS_IFORK_PTR(ip, whichfork);

        ASSERT(*idx >= 0);
        ASSERT(*idx <= xfs_iext_count(ifp));
        ASSERT(!isnullstartblock(new->br_startblock));

        XFS_STATS_INC(mp, xs_add_exlist);

#define LEFT            r[0]
#define RIGHT           r[1]
#define PREV            r[2]

        /*
         * Set up a bunch of variables to make the tests simpler.
         */
        error = 0;
        xfs_iext_get_extent(ifp, *idx, &PREV);
        ASSERT(new->br_state != PREV.br_state);
        new_endoff = new->br_startoff + new->br_blockcount;
        ASSERT(PREV.br_startoff <= new->br_startoff);
        ASSERT(PREV.br_startoff + PREV.br_blockcount >= new_endoff);

        /*
         * Set flags determining what part of the previous oldext allocation
         * extent is being replaced by a newext allocation.
         */
        if (PREV.br_startoff == new->br_startoff)
                state |= BMAP_LEFT_FILLING;
        if (PREV.br_startoff + PREV.br_blockcount == new_endoff)
                state |= BMAP_RIGHT_FILLING;

        /*
         * Check and set flags if this segment has a left neighbor.
         * Don't set contiguous if the combined extent would be too large.
         */
        if (*idx > 0) {
                state |= BMAP_LEFT_VALID;
                xfs_iext_get_extent(ifp, *idx - 1, &LEFT);

                if (isnullstartblock(LEFT.br_startblock))
                        state |= BMAP_LEFT_DELAY;
        }

        if ((state & BMAP_LEFT_VALID) && !(state & BMAP_LEFT_DELAY) &&
            LEFT.br_startoff + LEFT.br_blockcount == new->br_startoff &&
            LEFT.br_startblock + LEFT.br_blockcount == new->br_startblock &&
            LEFT.br_state == new->br_state &&
            LEFT.br_blockcount + new->br_blockcount <= MAXEXTLEN)
                state |= BMAP_LEFT_CONTIG;

        /*
         * Check and set flags if this segment has a right neighbor.
         * Don't set contiguous if the combined extent would be too large.
         * Also check for all-three-contiguous being too large.
         */
        if (*idx < xfs_iext_count(ifp) - 1) {
                state |= BMAP_RIGHT_VALID;
                xfs_iext_get_extent(ifp, *idx + 1, &RIGHT);
                if (isnullstartblock(RIGHT.br_startblock))
                        state |= BMAP_RIGHT_DELAY;
        }

        if ((state & BMAP_RIGHT_VALID) && !(state & BMAP_RIGHT_DELAY) &&
            new_endoff == RIGHT.br_startoff &&
            new->br_startblock + new->br_blockcount == RIGHT.br_startblock &&
            new->br_state == RIGHT.br_state &&
            new->br_blockcount + RIGHT.br_blockcount <= MAXEXTLEN &&
            ((state & (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
                       BMAP_RIGHT_FILLING)) !=
                      (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
                       BMAP_RIGHT_FILLING) ||
             LEFT.br_blockcount + new->br_blockcount + RIGHT.br_blockcount
                        <= MAXEXTLEN))
                state |= BMAP_RIGHT_CONTIG;

        /*
         * Switch out based on the FILLING and CONTIG state bits.
         */
        switch (state & (BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG |
                         BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG)) {
        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG |
             BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Setting all of a previous oldext extent to newext.
                 * The left and right neighbors are both contiguous with new.
                 */
                --*idx;

                LEFT.br_blockcount += PREV.br_blockcount + RIGHT.br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &LEFT);

                xfs_iext_remove(ip, *idx + 1, 2, state);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) - 2);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &RIGHT, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_delete(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_decrement(cur, 0, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_delete(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_decrement(cur, 0, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &LEFT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG:
                /*
                 * Setting all of a previous oldext extent to newext.
                 * The left neighbor is contiguous, the right is not.
                 */
                --*idx;

                LEFT.br_blockcount += PREV.br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &LEFT);

                xfs_iext_remove(ip, *idx + 1, 1, state);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &PREV, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_delete(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_decrement(cur, 0, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &LEFT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Setting all of a previous oldext extent to newext.
                 * The right neighbor is contiguous, the left is not.
                 */
                PREV.br_blockcount += RIGHT.br_blockcount;
                PREV.br_state = new->br_state;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                xfs_iext_remove(ip, *idx + 1, 1, state);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &RIGHT, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_delete(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        if ((error = xfs_btree_decrement(cur, 0, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING:
                /*
                 * Setting all of a previous oldext extent to newext.
                 * Neither the left nor right neighbors are contiguous with
                 * the new one.
                 */
                PREV.br_state = new->br_state;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                if (cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG:
                /*
                 * Setting the first part of a previous oldext extent to newext.
                 * The left neighbor is contiguous.
                 */
                LEFT.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx - 1, &LEFT);

                old = PREV;
                PREV.br_startoff += new->br_blockcount;
                PREV.br_startblock += new->br_blockcount;
                PREV.br_blockcount -= new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                --*idx;

                if (cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                        error = xfs_btree_decrement(cur, 0, &i);
                        if (error)
                                goto done;
                        error = xfs_bmbt_update(cur, &LEFT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_FILLING:
                /*
                 * Setting the first part of a previous oldext extent to newext.
                 * The left neighbor is not contiguous.
                 */
                old = PREV;
                PREV.br_startoff += new->br_blockcount;
                PREV.br_startblock += new->br_blockcount;
                PREV.br_blockcount -= new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                xfs_iext_insert(ip, *idx, 1, new, state);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                        cur->bc_rec.b = *new;
                        if ((error = xfs_btree_insert(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }
                break;

        case BMAP_RIGHT_FILLING | BMAP_RIGHT_CONTIG:
                /*
                 * Setting the last part of a previous oldext extent to newext.
                 * The right neighbor is contiguous with the new allocation.
                 */
                old = PREV;
                PREV.br_blockcount -= new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                ++*idx;

                RIGHT.br_startoff = new->br_startoff;
                RIGHT.br_startblock = new->br_startblock;
                RIGHT.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &RIGHT);

                if (cur == NULL)
                        rval = XFS_ILOG_DEXT;
                else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                        error = xfs_btree_increment(cur, 0, &i);
                        if (error)
                                goto done;
                        error = xfs_bmbt_update(cur, &RIGHT);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_RIGHT_FILLING:
                /*
                 * Setting the last part of a previous oldext extent to newext.
                 * The right neighbor is not contiguous.
                 */
                old = PREV;
                PREV.br_blockcount -= new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                ++*idx;
                xfs_iext_insert(ip, *idx, 1, new, state);

                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &PREV);
                        if (error)
                                goto done;
                        error = xfs_bmbt_lookup_eq(cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        if ((error = xfs_btree_insert(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }
                break;

        case 0:
                /*
                 * Setting the middle part of a previous oldext extent to
                 * newext.  Contiguity is impossible here.
                 * One extent becomes three extents.
                 */
                old = PREV;
                PREV.br_blockcount = new->br_startoff - PREV.br_startoff;
                xfs_iext_update_extent(ip, state, *idx, &PREV);

                r[0] = *new;
                r[1].br_startoff = new_endoff;
                r[1].br_blockcount =
                        old.br_startoff + old.br_blockcount - new_endoff;
                r[1].br_startblock = new->br_startblock + new->br_blockcount;
                r[1].br_state = PREV.br_state;

                ++*idx;
                xfs_iext_insert(ip, *idx, 2, &r[0], state);

                XFS_IFORK_NEXT_SET(ip, whichfork,
                                XFS_IFORK_NEXTENTS(ip, whichfork) + 2);
                if (cur == NULL)
                        rval = XFS_ILOG_CORE | XFS_ILOG_DEXT;
                else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        /* new right extent - oldext */
                        error = xfs_bmbt_update(cur, &r[1]);
                        if (error)
                                goto done;
                        /* new left extent - oldext */
                        cur->bc_rec.b = PREV;
                        if ((error = xfs_btree_insert(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        /*
                         * Reset the cursor to the position of the new extent
                         * we are about to insert as we can't trust it after
                         * the previous insert.
                         */
                        error = xfs_bmbt_lookup_eq(cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        /* new middle extent - newext */
                        if ((error = xfs_btree_insert(cur, &i)))
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }
                break;

        case BMAP_LEFT_FILLING | BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_LEFT_FILLING | BMAP_RIGHT_CONTIG:
        case BMAP_RIGHT_FILLING | BMAP_LEFT_CONTIG:
        case BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
        case BMAP_LEFT_CONTIG:
        case BMAP_RIGHT_CONTIG:
                /*
                 * These cases are all impossible.
                 */
                ASSERT(0);
        }

        /* update reverse mappings */
        error = xfs_rmap_convert_extent(mp, dfops, ip, whichfork, new);
        if (error)
                goto done;

        /* convert to a btree if necessary */
        if (xfs_bmap_needs_btree(ip, whichfork)) {
                int     tmp_logflags;   /* partial log flag return val */

                ASSERT(cur == NULL);
                error = xfs_bmap_extents_to_btree(tp, ip, first, dfops, &cur,
                                0, &tmp_logflags, whichfork);
                *logflagsp |= tmp_logflags;
                if (error)
                        goto done;
        }

        /* clear out the allocated field, done with it now in any case. */
        if (cur) {
                cur->bc_private.b.allocated = 0;
                *curp = cur;
        }

        xfs_bmap_check_leaf_extents(*curp, ip, whichfork);
done:
        *logflagsp |= rval;
        return error;
#undef  LEFT
#undef  RIGHT
#undef  PREV
}

/*
 * Convert a hole to a delayed allocation.
 */
STATIC void
xfs_bmap_add_extent_hole_delay(
        xfs_inode_t             *ip,    /* incore inode pointer */
        int                     whichfork,
        xfs_extnum_t            *idx,   /* extent number to update/insert */
        xfs_bmbt_irec_t         *new)   /* new data to add to file extents */
{
        xfs_ifork_t             *ifp;   /* inode fork pointer */
        xfs_bmbt_irec_t         left;   /* left neighbor extent entry */
        xfs_filblks_t           newlen=0;       /* new indirect size */
        xfs_filblks_t           oldlen=0;       /* old indirect size */
        xfs_bmbt_irec_t         right;  /* right neighbor extent entry */
        int                     state = xfs_bmap_fork_to_state(whichfork);
        xfs_filblks_t           temp;    /* temp for indirect calculations */

        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(isnullstartblock(new->br_startblock));

        /*
         * Check and set flags if this segment has a left neighbor
         */
        if (*idx > 0) {
                state |= BMAP_LEFT_VALID;
                xfs_iext_get_extent(ifp, *idx - 1, &left);

                if (isnullstartblock(left.br_startblock))
                        state |= BMAP_LEFT_DELAY;
        }

        /*
         * Check and set flags if the current (right) segment exists.
         * If it doesn't exist, we're converting the hole at end-of-file.
         */
        if (*idx < xfs_iext_count(ifp)) {
                state |= BMAP_RIGHT_VALID;
                xfs_iext_get_extent(ifp, *idx, &right);

                if (isnullstartblock(right.br_startblock))
                        state |= BMAP_RIGHT_DELAY;
        }

        /*
         * Set contiguity flags on the left and right neighbors.
         * Don't let extents get too large, even if the pieces are contiguous.
         */
        if ((state & BMAP_LEFT_VALID) && (state & BMAP_LEFT_DELAY) &&
            left.br_startoff + left.br_blockcount == new->br_startoff &&
            left.br_blockcount + new->br_blockcount <= MAXEXTLEN)
                state |= BMAP_LEFT_CONTIG;

        if ((state & BMAP_RIGHT_VALID) && (state & BMAP_RIGHT_DELAY) &&
            new->br_startoff + new->br_blockcount == right.br_startoff &&
            new->br_blockcount + right.br_blockcount <= MAXEXTLEN &&
            (!(state & BMAP_LEFT_CONTIG) ||
             (left.br_blockcount + new->br_blockcount +
              right.br_blockcount <= MAXEXTLEN)))
                state |= BMAP_RIGHT_CONTIG;

        /*
         * Switch out based on the contiguity flags.
         */
        switch (state & (BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG)) {
        case BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
                /*
                 * New allocation is contiguous with delayed allocations
                 * on the left and on the right.
                 * Merge all three into a single extent record.
                 */
                --*idx;
                temp = left.br_blockcount + new->br_blockcount +
                        right.br_blockcount;

                oldlen = startblockval(left.br_startblock) +
                        startblockval(new->br_startblock) +
                        startblockval(right.br_startblock);
                newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp),
                                         oldlen);
                left.br_startblock = nullstartblock(newlen);
                left.br_blockcount = temp;
                xfs_iext_update_extent(ip, state, *idx, &left);

                xfs_iext_remove(ip, *idx + 1, 1, state);
                break;

        case BMAP_LEFT_CONTIG:
                /*
                 * New allocation is contiguous with a delayed allocation
                 * on the left.
                 * Merge the new allocation with the left neighbor.
                 */
                --*idx;
                temp = left.br_blockcount + new->br_blockcount;

                oldlen = startblockval(left.br_startblock) +
                        startblockval(new->br_startblock);
                newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp),
                                         oldlen);
                left.br_blockcount = temp;
                left.br_startblock = nullstartblock(newlen);
                xfs_iext_update_extent(ip, state, *idx, &left);
                break;

        case BMAP_RIGHT_CONTIG:
                /*
                 * New allocation is contiguous with a delayed allocation
                 * on the right.
                 * Merge the new allocation with the right neighbor.
                 */
                temp = new->br_blockcount + right.br_blockcount;
                oldlen = startblockval(new->br_startblock) +
                        startblockval(right.br_startblock);
                newlen = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip, temp),
                                         oldlen);
                right.br_startoff = new->br_startoff;
                right.br_startblock = nullstartblock(newlen);
                right.br_blockcount = temp;
                xfs_iext_update_extent(ip, state, *idx, &right);
                break;

        case 0:
                /*
                 * New allocation is not contiguous with another
                 * delayed allocation.
                 * Insert a new entry.
                 */
                oldlen = newlen = 0;
                xfs_iext_insert(ip, *idx, 1, new, state);
                break;
        }
        if (oldlen != newlen) {
                ASSERT(oldlen > newlen);
                xfs_mod_fdblocks(ip->i_mount, (int64_t)(oldlen - newlen),
                                 false);
                /*
                 * Nothing to do for disk quota accounting here.
                 */
        }
}

/*
 * Convert a hole to a real allocation.
 */
STATIC int                              /* error */
xfs_bmap_add_extent_hole_real(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_extnum_t            *idx,
        struct xfs_btree_cur    **curp,
        struct xfs_bmbt_irec    *new,
        xfs_fsblock_t           *first,
        struct xfs_defer_ops    *dfops,
        int                     *logflagsp)
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_btree_cur    *cur = *curp;
        int                     error;  /* error return value */
        int                     i;      /* temp state */
        xfs_bmbt_irec_t         left;   /* left neighbor extent entry */
        xfs_bmbt_irec_t         right;  /* right neighbor extent entry */
        int                     rval=0; /* return value (logging flags) */
        int                     state = xfs_bmap_fork_to_state(whichfork);
        struct xfs_bmbt_irec    old;

        ASSERT(*idx >= 0);
        ASSERT(*idx <= xfs_iext_count(ifp));
        ASSERT(!isnullstartblock(new->br_startblock));
        ASSERT(!cur || !(cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL));

        XFS_STATS_INC(mp, xs_add_exlist);

        /*
         * Check and set flags if this segment has a left neighbor.
         */
        if (*idx > 0) {
                state |= BMAP_LEFT_VALID;
                xfs_iext_get_extent(ifp, *idx - 1, &left);
                if (isnullstartblock(left.br_startblock))
                        state |= BMAP_LEFT_DELAY;
        }

        /*
         * Check and set flags if this segment has a current value.
         * Not true if we're inserting into the "hole" at eof.
         */
        if (*idx < xfs_iext_count(ifp)) {
                state |= BMAP_RIGHT_VALID;
                xfs_iext_get_extent(ifp, *idx, &right);
                if (isnullstartblock(right.br_startblock))
                        state |= BMAP_RIGHT_DELAY;
        }

        /*
         * We're inserting a real allocation between "left" and "right".
         * Set the contiguity flags.  Don't let extents get too large.
         */
        if ((state & BMAP_LEFT_VALID) && !(state & BMAP_LEFT_DELAY) &&
            left.br_startoff + left.br_blockcount == new->br_startoff &&
            left.br_startblock + left.br_blockcount == new->br_startblock &&
            left.br_state == new->br_state &&
            left.br_blockcount + new->br_blockcount <= MAXEXTLEN)
                state |= BMAP_LEFT_CONTIG;

        if ((state & BMAP_RIGHT_VALID) && !(state & BMAP_RIGHT_DELAY) &&
            new->br_startoff + new->br_blockcount == right.br_startoff &&
            new->br_startblock + new->br_blockcount == right.br_startblock &&
            new->br_state == right.br_state &&
            new->br_blockcount + right.br_blockcount <= MAXEXTLEN &&
            (!(state & BMAP_LEFT_CONTIG) ||
             left.br_blockcount + new->br_blockcount +
             right.br_blockcount <= MAXEXTLEN))
                state |= BMAP_RIGHT_CONTIG;

        error = 0;
        /*
         * Select which case we're in here, and implement it.
         */
        switch (state & (BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG)) {
        case BMAP_LEFT_CONTIG | BMAP_RIGHT_CONTIG:
                /*
                 * New allocation is contiguous with real allocations on the
                 * left and on the right.
                 * Merge all three into a single extent record.
                 */
                --*idx;
                left.br_blockcount += new->br_blockcount + right.br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &left);

                xfs_iext_remove(ip, *idx + 1, 1, state);

                XFS_IFORK_NEXT_SET(ip, whichfork,
                        XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
                if (cur == NULL) {
                        rval = XFS_ILOG_CORE | xfs_ilog_fext(whichfork);
                } else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, &right, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_btree_delete(cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_btree_decrement(cur, 0, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &left);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_LEFT_CONTIG:
                /*
                 * New allocation is contiguous with a real allocation
                 * on the left.
                 * Merge the new allocation with the left neighbor.
                 */
                --*idx;
                old = left;

                left.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &left);

                if (cur == NULL) {
                        rval = xfs_ilog_fext(whichfork);
                } else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &left);
                        if (error)
                                goto done;
                }
                break;

        case BMAP_RIGHT_CONTIG:
                /*
                 * New allocation is contiguous with a real allocation
                 * on the right.
                 * Merge the new allocation with the right neighbor.
                 */
                old = right;

                right.br_startoff = new->br_startoff;
                right.br_startblock = new->br_startblock;
                right.br_blockcount += new->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &right);

                if (cur == NULL) {
                        rval = xfs_ilog_fext(whichfork);
                } else {
                        rval = 0;
                        error = xfs_bmbt_lookup_eq(cur, &old, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                        error = xfs_bmbt_update(cur, &right);
                        if (error)
                                goto done;
                }
                break;

        case 0:
                /*
                 * New allocation is not contiguous with another
                 * real allocation.
                 * Insert a new entry.
                 */
                xfs_iext_insert(ip, *idx, 1, new, state);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                        XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
                if (cur == NULL) {
                        rval = XFS_ILOG_CORE | xfs_ilog_fext(whichfork);
                } else {
                        rval = XFS_ILOG_CORE;
                        error = xfs_bmbt_lookup_eq(cur, new, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 0, done);
                        error = xfs_btree_insert(cur, &i);
                        if (error)
                                goto done;
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                }
                break;
        }

        /* add reverse mapping */
        error = xfs_rmap_map_extent(mp, dfops, ip, whichfork, new);
        if (error)
                goto done;

        /* convert to a btree if necessary */
        if (xfs_bmap_needs_btree(ip, whichfork)) {
                int     tmp_logflags;   /* partial log flag return val */

                ASSERT(cur == NULL);
                error = xfs_bmap_extents_to_btree(tp, ip, first, dfops, curp,
                                0, &tmp_logflags, whichfork);
                *logflagsp |= tmp_logflags;
                cur = *curp;
                if (error)
                        goto done;
        }

        /* clear out the allocated field, done with it now in any case. */
        if (cur)
                cur->bc_private.b.allocated = 0;

        xfs_bmap_check_leaf_extents(cur, ip, whichfork);
done:
        *logflagsp |= rval;
        return error;
}

/*
 * Functions used in the extent read, allocate and remove paths
 */

/*
 * Adjust the size of the new extent based on di_extsize and rt extsize.
 */
int
xfs_bmap_extsize_align(
        xfs_mount_t     *mp,
        xfs_bmbt_irec_t *gotp,          /* next extent pointer */
        xfs_bmbt_irec_t *prevp,         /* previous extent pointer */
        xfs_extlen_t    extsz,          /* align to this extent size */
        int             rt,             /* is this a realtime inode? */
        int             eof,            /* is extent at end-of-file? */
        int             delay,          /* creating delalloc extent? */
        int             convert,        /* overwriting unwritten extent? */
        xfs_fileoff_t   *offp,          /* in/out: aligned offset */
        xfs_extlen_t    *lenp)          /* in/out: aligned length */
{
        xfs_fileoff_t   orig_off;       /* original offset */
        xfs_extlen_t    orig_alen;      /* original length */
        xfs_fileoff_t   orig_end;       /* original off+len */
        xfs_fileoff_t   nexto;          /* next file offset */
        xfs_fileoff_t   prevo;          /* previous file offset */
        xfs_fileoff_t   align_off;      /* temp for offset */
        xfs_extlen_t    align_alen;     /* temp for length */
        xfs_extlen_t    temp;           /* temp for calculations */

        if (convert)
                return 0;

        orig_off = align_off = *offp;
        orig_alen = align_alen = *lenp;
        orig_end = orig_off + orig_alen;

        /*
         * If this request overlaps an existing extent, then don't
         * attempt to perform any additional alignment.
         */
        if (!delay && !eof &&
            (orig_off >= gotp->br_startoff) &&
            (orig_end <= gotp->br_startoff + gotp->br_blockcount)) {
                return 0;
        }

        /*
         * If the file offset is unaligned vs. the extent size
         * we need to align it.  This will be possible unless
         * the file was previously written with a kernel that didn't
         * perform this alignment, or if a truncate shot us in the
         * foot.
         */
        temp = do_mod(orig_off, extsz);
        if (temp) {
                align_alen += temp;
                align_off -= temp;
        }

        /* Same adjustment for the end of the requested area. */
        temp = (align_alen % extsz);
        if (temp)
                align_alen += extsz - temp;

        /*
         * For large extent hint sizes, the aligned extent might be larger than
         * MAXEXTLEN. In that case, reduce the size by an extsz so that it pulls
         * the length back under MAXEXTLEN. The outer allocation loops handle
         * short allocation just fine, so it is safe to do this. We only want to
         * do it when we are forced to, though, because it means more allocation
         * operations are required.
         */
        while (align_alen > MAXEXTLEN)
                align_alen -= extsz;
        ASSERT(align_alen <= MAXEXTLEN);

        /*
         * If the previous block overlaps with this proposed allocation
         * then move the start forward without adjusting the length.
         */
        if (prevp->br_startoff != NULLFILEOFF) {
                if (prevp->br_startblock == HOLESTARTBLOCK)
                        prevo = prevp->br_startoff;
                else
                        prevo = prevp->br_startoff + prevp->br_blockcount;
        } else
                prevo = 0;
        if (align_off != orig_off && align_off < prevo)
                align_off = prevo;
        /*
         * If the next block overlaps with this proposed allocation
         * then move the start back without adjusting the length,
         * but not before offset 0.
         * This may of course make the start overlap previous block,
         * and if we hit the offset 0 limit then the next block
         * can still overlap too.
         */
        if (!eof && gotp->br_startoff != NULLFILEOFF) {
                if ((delay && gotp->br_startblock == HOLESTARTBLOCK) ||
                    (!delay && gotp->br_startblock == DELAYSTARTBLOCK))
                        nexto = gotp->br_startoff + gotp->br_blockcount;
                else
                        nexto = gotp->br_startoff;
        } else
                nexto = NULLFILEOFF;
        if (!eof &&
            align_off + align_alen != orig_end &&
            align_off + align_alen > nexto)
                align_off = nexto > align_alen ? nexto - align_alen : 0;
        /*
         * If we're now overlapping the next or previous extent that
         * means we can't fit an extsz piece in this hole.  Just move
         * the start forward to the first valid spot and set
         * the length so we hit the end.
         */
        if (align_off != orig_off && align_off < prevo)
                align_off = prevo;
        if (align_off + align_alen != orig_end &&
            align_off + align_alen > nexto &&
            nexto != NULLFILEOFF) {
                ASSERT(nexto > prevo);
                align_alen = nexto - align_off;
        }

        /*
         * If realtime, and the result isn't a multiple of the realtime
         * extent size we need to remove blocks until it is.
         */
        if (rt && (temp = (align_alen % mp->m_sb.sb_rextsize))) {
                /*
                 * We're not covering the original request, or
                 * we won't be able to once we fix the length.
                 */
                if (orig_off < align_off ||
                    orig_end > align_off + align_alen ||
                    align_alen - temp < orig_alen)
                        return -EINVAL;
                /*
                 * Try to fix it by moving the start up.
                 */
                if (align_off + temp <= orig_off) {
                        align_alen -= temp;
                        align_off += temp;
                }
                /*
                 * Try to fix it by moving the end in.
                 */
                else if (align_off + align_alen - temp >= orig_end)
                        align_alen -= temp;
                /*
                 * Set the start to the minimum then trim the length.
                 */
                else {
                        align_alen -= orig_off - align_off;
                        align_off = orig_off;
                        align_alen -= align_alen % mp->m_sb.sb_rextsize;
                }
                /*
                 * Result doesn't cover the request, fail it.
                 */
                if (orig_off < align_off || orig_end > align_off + align_alen)
                        return -EINVAL;
        } else {
                ASSERT(orig_off >= align_off);
                /* see MAXEXTLEN handling above */
                ASSERT(orig_end <= align_off + align_alen ||
                       align_alen + extsz > MAXEXTLEN);
        }

#ifdef DEBUG
        if (!eof && gotp->br_startoff != NULLFILEOFF)
                ASSERT(align_off + align_alen <= gotp->br_startoff);
        if (prevp->br_startoff != NULLFILEOFF)
                ASSERT(align_off >= prevp->br_startoff + prevp->br_blockcount);
#endif

        *lenp = align_alen;
        *offp = align_off;
        return 0;
}

#define XFS_ALLOC_GAP_UNITS     4

void
xfs_bmap_adjacent(
        struct xfs_bmalloca     *ap)    /* bmap alloc argument struct */
{
        xfs_fsblock_t   adjust;         /* adjustment to block numbers */
        xfs_agnumber_t  fb_agno;        /* ag number of ap->firstblock */
        xfs_mount_t     *mp;            /* mount point structure */
        int             nullfb;         /* true if ap->firstblock isn't set */
        int             rt;             /* true if inode is realtime */

#define ISVALID(x,y)    \
        (rt ? \
                (x) < mp->m_sb.sb_rblocks : \
                XFS_FSB_TO_AGNO(mp, x) == XFS_FSB_TO_AGNO(mp, y) && \
                XFS_FSB_TO_AGNO(mp, x) < mp->m_sb.sb_agcount && \
                XFS_FSB_TO_AGBNO(mp, x) < mp->m_sb.sb_agblocks)

        mp = ap->ip->i_mount;
        nullfb = *ap->firstblock == NULLFSBLOCK;
        rt = XFS_IS_REALTIME_INODE(ap->ip) &&
                xfs_alloc_is_userdata(ap->datatype);
        fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, *ap->firstblock);
        /*
         * If allocating at eof, and there's a previous real block,
         * try to use its last block as our starting point.
         */
        if (ap->eof && ap->prev.br_startoff != NULLFILEOFF &&
            !isnullstartblock(ap->prev.br_startblock) &&
            ISVALID(ap->prev.br_startblock + ap->prev.br_blockcount,
                    ap->prev.br_startblock)) {
                ap->blkno = ap->prev.br_startblock + ap->prev.br_blockcount;
                /*
                 * Adjust for the gap between prevp and us.
                 */
                adjust = ap->offset -
                        (ap->prev.br_startoff + ap->prev.br_blockcount);
                if (adjust &&
                    ISVALID(ap->blkno + adjust, ap->prev.br_startblock))
                        ap->blkno += adjust;
        }
        /*
         * If not at eof, then compare the two neighbor blocks.
         * Figure out whether either one gives us a good starting point,
         * and pick the better one.
         */
        else if (!ap->eof) {
                xfs_fsblock_t   gotbno;         /* right side block number */
                xfs_fsblock_t   gotdiff=0;      /* right side difference */
                xfs_fsblock_t   prevbno;        /* left side block number */
                xfs_fsblock_t   prevdiff=0;     /* left side difference */

                /*
                 * If there's a previous (left) block, select a requested
                 * start block based on it.
                 */
                if (ap->prev.br_startoff != NULLFILEOFF &&
                    !isnullstartblock(ap->prev.br_startblock) &&
                    (prevbno = ap->prev.br_startblock +
                               ap->prev.br_blockcount) &&
                    ISVALID(prevbno, ap->prev.br_startblock)) {
                        /*
                         * Calculate gap to end of previous block.
                         */
                        adjust = prevdiff = ap->offset -
                                (ap->prev.br_startoff +
                                 ap->prev.br_blockcount);
                        /*
                         * Figure the startblock based on the previous block's
                         * end and the gap size.
                         * Heuristic!
                         * If the gap is large relative to the piece we're
                         * allocating, or using it gives us an invalid block
                         * number, then just use the end of the previous block.
                         */
                        if (prevdiff <= XFS_ALLOC_GAP_UNITS * ap->length &&
                            ISVALID(prevbno + prevdiff,
                                    ap->prev.br_startblock))
                                prevbno += adjust;
                        else
                                prevdiff += adjust;
                        /*
                         * If the firstblock forbids it, can't use it,
                         * must use default.
                         */
                        if (!rt && !nullfb &&
                            XFS_FSB_TO_AGNO(mp, prevbno) != fb_agno)
                                prevbno = NULLFSBLOCK;
                }
                /*
                 * No previous block or can't follow it, just default.
                 */
                else
                        prevbno = NULLFSBLOCK;
                /*
                 * If there's a following (right) block, select a requested
                 * start block based on it.
                 */
                if (!isnullstartblock(ap->got.br_startblock)) {
                        /*
                         * Calculate gap to start of next block.
                         */
                        adjust = gotdiff = ap->got.br_startoff - ap->offset;
                        /*
                         * Figure the startblock based on the next block's
                         * start and the gap size.
                         */
                        gotbno = ap->got.br_startblock;
                        /*
                         * Heuristic!
                         * If the gap is large relative to the piece we're
                         * allocating, or using it gives us an invalid block
                         * number, then just use the start of the next block
                         * offset by our length.
                         */
                        if (gotdiff <= XFS_ALLOC_GAP_UNITS * ap->length &&
                            ISVALID(gotbno - gotdiff, gotbno))
                                gotbno -= adjust;
                        else if (ISVALID(gotbno - ap->length, gotbno)) {
                                gotbno -= ap->length;
                                gotdiff += adjust - ap->length;
                        } else
                                gotdiff += adjust;
                        /*
                         * If the firstblock forbids it, can't use it,
                         * must use default.
                         */
                        if (!rt && !nullfb &&
                            XFS_FSB_TO_AGNO(mp, gotbno) != fb_agno)
                                gotbno = NULLFSBLOCK;
                }
                /*
                 * No next block, just default.
                 */
                else
                        gotbno = NULLFSBLOCK;
                /*
                 * If both valid, pick the better one, else the only good
                 * one, else ap->blkno is already set (to 0 or the inode block).
                 */
                if (prevbno != NULLFSBLOCK && gotbno != NULLFSBLOCK)
                        ap->blkno = prevdiff <= gotdiff ? prevbno : gotbno;
                else if (prevbno != NULLFSBLOCK)
                        ap->blkno = prevbno;
                else if (gotbno != NULLFSBLOCK)
                        ap->blkno = gotbno;
        }
#undef ISVALID
}

static int
xfs_bmap_longest_free_extent(
        struct xfs_trans        *tp,
        xfs_agnumber_t          ag,
        xfs_extlen_t            *blen,
        int                     *notinit)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_perag        *pag;
        xfs_extlen_t            longest;
        int                     error = 0;

        pag = xfs_perag_get(mp, ag);
        if (!pag->pagf_init) {
                error = xfs_alloc_pagf_init(mp, tp, ag, XFS_ALLOC_FLAG_TRYLOCK);
                if (error)
                        goto out;

                if (!pag->pagf_init) {
                        *notinit = 1;
                        goto out;
                }
        }

        longest = xfs_alloc_longest_free_extent(mp, pag,
                                xfs_alloc_min_freelist(mp, pag),
                                xfs_ag_resv_needed(pag, XFS_AG_RESV_NONE));
        if (*blen < longest)
                *blen = longest;

out:
        xfs_perag_put(pag);
        return error;
}

static void
xfs_bmap_select_minlen(
        struct xfs_bmalloca     *ap,
        struct xfs_alloc_arg    *args,
        xfs_extlen_t            *blen,
        int                     notinit)
{
        if (notinit || *blen < ap->minlen) {
                /*
                 * Since we did a BUF_TRYLOCK above, it is possible that
                 * there is space for this request.
                 */
                args->minlen = ap->minlen;
        } else if (*blen < args->maxlen) {
                /*
                 * If the best seen length is less than the request length,
                 * use the best as the minimum.
                 */
                args->minlen = *blen;
        } else {
                /*
                 * Otherwise we've seen an extent as big as maxlen, use that
                 * as the minimum.
                 */
                args->minlen = args->maxlen;
        }
}

STATIC int
xfs_bmap_btalloc_nullfb(
        struct xfs_bmalloca     *ap,
        struct xfs_alloc_arg    *args,
        xfs_extlen_t            *blen)
{
        struct xfs_mount        *mp = ap->ip->i_mount;
        xfs_agnumber_t          ag, startag;
        int                     notinit = 0;
        int                     error;

        args->type = XFS_ALLOCTYPE_START_BNO;
        args->total = ap->total;

        startag = ag = XFS_FSB_TO_AGNO(mp, args->fsbno);
        if (startag == NULLAGNUMBER)
                startag = ag = 0;

        while (*blen < args->maxlen) {
                error = xfs_bmap_longest_free_extent(args->tp, ag, blen,
                                                     &notinit);
                if (error)
                        return error;

                if (++ag == mp->m_sb.sb_agcount)
                        ag = 0;
                if (ag == startag)
                        break;
        }

        xfs_bmap_select_minlen(ap, args, blen, notinit);
        return 0;
}

STATIC int
xfs_bmap_btalloc_filestreams(
        struct xfs_bmalloca     *ap,
        struct xfs_alloc_arg    *args,
        xfs_extlen_t            *blen)
{
        struct xfs_mount        *mp = ap->ip->i_mount;
        xfs_agnumber_t          ag;
        int                     notinit = 0;
        int                     error;

        args->type = XFS_ALLOCTYPE_NEAR_BNO;
        args->total = ap->total;

        ag = XFS_FSB_TO_AGNO(mp, args->fsbno);
        if (ag == NULLAGNUMBER)
                ag = 0;

        error = xfs_bmap_longest_free_extent(args->tp, ag, blen, &notinit);
        if (error)
                return error;

        if (*blen < args->maxlen) {
                error = xfs_filestream_new_ag(ap, &ag);
                if (error)
                        return error;

                error = xfs_bmap_longest_free_extent(args->tp, ag, blen,
                                                     &notinit);
                if (error)
                        return error;

        }

        xfs_bmap_select_minlen(ap, args, blen, notinit);

        /*
         * Set the failure fallback case to look in the selected AG as stream
         * may have moved.
         */
        ap->blkno = args->fsbno = XFS_AGB_TO_FSB(mp, ag, 0);
        return 0;
}

STATIC int
xfs_bmap_btalloc(
        struct xfs_bmalloca     *ap)    /* bmap alloc argument struct */
{
        xfs_mount_t     *mp;            /* mount point structure */
        xfs_alloctype_t atype = 0;      /* type for allocation routines */
        xfs_extlen_t    align = 0;      /* minimum allocation alignment */
        xfs_agnumber_t  fb_agno;        /* ag number of ap->firstblock */
        xfs_agnumber_t  ag;
        xfs_alloc_arg_t args;
        xfs_extlen_t    blen;
        xfs_extlen_t    nextminlen = 0;
        int             nullfb;         /* true if ap->firstblock isn't set */
        int             isaligned;
        int             tryagain;
        int             error;
        int             stripe_align;

        ASSERT(ap->length);

        mp = ap->ip->i_mount;

        /* stripe alignment for allocation is determined by mount parameters */
        stripe_align = 0;
        if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
                stripe_align = mp->m_swidth;
        else if (mp->m_dalign)
                stripe_align = mp->m_dalign;

        if (ap->flags & XFS_BMAPI_COWFORK)
                align = xfs_get_cowextsz_hint(ap->ip);
        else if (xfs_alloc_is_userdata(ap->datatype))
                align = xfs_get_extsz_hint(ap->ip);
        if (align) {
                error = xfs_bmap_extsize_align(mp, &ap->got, &ap->prev,
                                                align, 0, ap->eof, 0, ap->conv,
                                                &ap->offset, &ap->length);
                ASSERT(!error);
                ASSERT(ap->length);
        }


        nullfb = *ap->firstblock == NULLFSBLOCK;
        fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, *ap->firstblock);
        if (nullfb) {
                if (xfs_alloc_is_userdata(ap->datatype) &&
                    xfs_inode_is_filestream(ap->ip)) {
                        ag = xfs_filestream_lookup_ag(ap->ip);
                        ag = (ag != NULLAGNUMBER) ? ag : 0;
                        ap->blkno = XFS_AGB_TO_FSB(mp, ag, 0);
                } else {
                        ap->blkno = XFS_INO_TO_FSB(mp, ap->ip->i_ino);
                }
        } else
                ap->blkno = *ap->firstblock;

        xfs_bmap_adjacent(ap);

        /*
         * If allowed, use ap->blkno; otherwise must use firstblock since
         * it's in the right allocation group.
         */
        if (nullfb || XFS_FSB_TO_AGNO(mp, ap->blkno) == fb_agno)
                ;
        else
                ap->blkno = *ap->firstblock;
        /*
         * Normal allocation, done through xfs_alloc_vextent.
         */
        tryagain = isaligned = 0;
        memset(&args, 0, sizeof(args));
        args.tp = ap->tp;
        args.mp = mp;
        args.fsbno = ap->blkno;
        xfs_rmap_skip_owner_update(&args.oinfo);

        /* Trim the allocation back to the maximum an AG can fit. */
        args.maxlen = MIN(ap->length, mp->m_ag_max_usable);
        args.firstblock = *ap->firstblock;
        blen = 0;
        if (nullfb) {
                /*
                 * Search for an allocation group with a single extent large
                 * enough for the request.  If one isn't found, then adjust
                 * the minimum allocation size to the largest space found.
                 */
                if (xfs_alloc_is_userdata(ap->datatype) &&
                    xfs_inode_is_filestream(ap->ip))
                        error = xfs_bmap_btalloc_filestreams(ap, &args, &blen);
                else
                        error = xfs_bmap_btalloc_nullfb(ap, &args, &blen);
                if (error)
                        return error;
        } else if (ap->dfops->dop_low) {
                if (xfs_inode_is_filestream(ap->ip))
                        args.type = XFS_ALLOCTYPE_FIRST_AG;
                else
                        args.type = XFS_ALLOCTYPE_START_BNO;
                args.total = args.minlen = ap->minlen;
        } else {
                args.type = XFS_ALLOCTYPE_NEAR_BNO;
                args.total = ap->total;
                args.minlen = ap->minlen;
        }
        /* apply extent size hints if obtained earlier */
        if (align) {
                args.prod = align;
                if ((args.mod = (xfs_extlen_t)do_mod(ap->offset, args.prod)))
                        args.mod = (xfs_extlen_t)(args.prod - args.mod);
        } else if (mp->m_sb.sb_blocksize >= PAGE_SIZE) {
                args.prod = 1;
                args.mod = 0;
        } else {
                args.prod = PAGE_SIZE >> mp->m_sb.sb_blocklog;
                if ((args.mod = (xfs_extlen_t)(do_mod(ap->offset, args.prod))))
                        args.mod = (xfs_extlen_t)(args.prod - args.mod);
        }
        /*
         * If we are not low on available data blocks, and the
         * underlying logical volume manager is a stripe, and
         * the file offset is zero then try to allocate data
         * blocks on stripe unit boundary.
         * NOTE: ap->aeof is only set if the allocation length
         * is >= the stripe unit and the allocation offset is
         * at the end of file.
         */
        if (!ap->dfops->dop_low && ap->aeof) {
                if (!ap->offset) {
                        args.alignment = stripe_align;
                        atype = args.type;
                        isaligned = 1;
                        /*
                         * Adjust for alignment
                         */
                        if (blen > args.alignment && blen <= args.maxlen)
                                args.minlen = blen - args.alignment;
                        args.minalignslop = 0;
                } else {
                        /*
                         * First try an exact bno allocation.
                         * If it fails then do a near or start bno
                         * allocation with alignment turned on.
                         */
                        atype = args.type;
                        tryagain = 1;
                        args.type = XFS_ALLOCTYPE_THIS_BNO;
                        args.alignment = 1;
                        /*
                         * Compute the minlen+alignment for the
                         * next case.  Set slop so that the value
                         * of minlen+alignment+slop doesn't go up
                         * between the calls.
                         */
                        if (blen > stripe_align && blen <= args.maxlen)
                                nextminlen = blen - stripe_align;
                        else
                                nextminlen = args.minlen;
                        if (nextminlen + stripe_align > args.minlen + 1)
                                args.minalignslop =
                                        nextminlen + stripe_align -
                                        args.minlen - 1;
                        else
                                args.minalignslop = 0;
                }
        } else {
                args.alignment = 1;
                args.minalignslop = 0;
        }
        args.minleft = ap->minleft;
        args.wasdel = ap->wasdel;
        args.resv = XFS_AG_RESV_NONE;
        args.datatype = ap->datatype;
        if (ap->datatype & XFS_ALLOC_USERDATA_ZERO)
                args.ip = ap->ip;

        error = xfs_alloc_vextent(&args);
        if (error)
                return error;

        if (tryagain && args.fsbno == NULLFSBLOCK) {
                /*
                 * Exact allocation failed. Now try with alignment
                 * turned on.
                 */
                args.type = atype;
                args.fsbno = ap->blkno;
                args.alignment = stripe_align;
                args.minlen = nextminlen;
                args.minalignslop = 0;
                isaligned = 1;
                if ((error = xfs_alloc_vextent(&args)))
                        return error;
        }
        if (isaligned && args.fsbno == NULLFSBLOCK) {
                /*
                 * allocation failed, so turn off alignment and
                 * try again.
                 */
                args.type = atype;
                args.fsbno = ap->blkno;
                args.alignment = 0;
                if ((error = xfs_alloc_vextent(&args)))
                        return error;
        }
        if (args.fsbno == NULLFSBLOCK && nullfb &&
            args.minlen > ap->minlen) {
                args.minlen = ap->minlen;
                args.type = XFS_ALLOCTYPE_START_BNO;
                args.fsbno = ap->blkno;
                if ((error = xfs_alloc_vextent(&args)))
                        return error;
        }
        if (args.fsbno == NULLFSBLOCK && nullfb) {
                args.fsbno = 0;
                args.type = XFS_ALLOCTYPE_FIRST_AG;
                args.total = ap->minlen;
                if ((error = xfs_alloc_vextent(&args)))
                        return error;
                ap->dfops->dop_low = true;
        }
        if (args.fsbno != NULLFSBLOCK) {
                /*
                 * check the allocation happened at the same or higher AG than
                 * the first block that was allocated.
                 */
                ASSERT(*ap->firstblock == NULLFSBLOCK ||
                       XFS_FSB_TO_AGNO(mp, *ap->firstblock) <=
                       XFS_FSB_TO_AGNO(mp, args.fsbno));

                ap->blkno = args.fsbno;
                if (*ap->firstblock == NULLFSBLOCK)
                        *ap->firstblock = args.fsbno;
                ASSERT(nullfb || fb_agno <= args.agno);
                ap->length = args.len;
                if (!(ap->flags & XFS_BMAPI_COWFORK))
                        ap->ip->i_d.di_nblocks += args.len;
                xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
                if (ap->wasdel)
                        ap->ip->i_delayed_blks -= args.len;
                /*
                 * Adjust the disk quota also. This was reserved
                 * earlier.
                 */
                xfs_trans_mod_dquot_byino(ap->tp, ap->ip,
                        ap->wasdel ? XFS_TRANS_DQ_DELBCOUNT :
                                        XFS_TRANS_DQ_BCOUNT,
                        (long) args.len);
        } else {
                ap->blkno = NULLFSBLOCK;
                ap->length = 0;
        }
        return 0;
}

/*
 * xfs_bmap_alloc is called by xfs_bmapi to allocate an extent for a file.
 * It figures out where to ask the underlying allocator to put the new extent.
 */
STATIC int
xfs_bmap_alloc(
        struct xfs_bmalloca     *ap)    /* bmap alloc argument struct */
{
        if (XFS_IS_REALTIME_INODE(ap->ip) &&
            xfs_alloc_is_userdata(ap->datatype))
                return xfs_bmap_rtalloc(ap);
        return xfs_bmap_btalloc(ap);
}

/* Trim extent to fit a logical block range. */
void
xfs_trim_extent(
        struct xfs_bmbt_irec    *irec,
        xfs_fileoff_t           bno,
        xfs_filblks_t           len)
{
        xfs_fileoff_t           distance;
        xfs_fileoff_t           end = bno + len;

        if (irec->br_startoff + irec->br_blockcount <= bno ||
            irec->br_startoff >= end) {
                irec->br_blockcount = 0;
                return;
        }

        if (irec->br_startoff < bno) {
                distance = bno - irec->br_startoff;
                if (isnullstartblock(irec->br_startblock))
                        irec->br_startblock = DELAYSTARTBLOCK;
                if (irec->br_startblock != DELAYSTARTBLOCK &&
                    irec->br_startblock != HOLESTARTBLOCK)
                        irec->br_startblock += distance;
                irec->br_startoff += distance;
                irec->br_blockcount -= distance;
        }

        if (end < irec->br_startoff + irec->br_blockcount) {
                distance = irec->br_startoff + irec->br_blockcount - end;
                irec->br_blockcount -= distance;
        }
}

/* trim extent to within eof */
void
xfs_trim_extent_eof(
        struct xfs_bmbt_irec    *irec,
        struct xfs_inode        *ip)

{
        xfs_trim_extent(irec, 0, XFS_B_TO_FSB(ip->i_mount,
                                              i_size_read(VFS_I(ip))));
}

/*
 * Trim the returned map to the required bounds
 */
STATIC void
xfs_bmapi_trim_map(
        struct xfs_bmbt_irec    *mval,
        struct xfs_bmbt_irec    *got,
        xfs_fileoff_t           *bno,
        xfs_filblks_t           len,
        xfs_fileoff_t           obno,
        xfs_fileoff_t           end,
        int                     n,
        int                     flags)
{
        if ((flags & XFS_BMAPI_ENTIRE) ||
            got->br_startoff + got->br_blockcount <= obno) {
                *mval = *got;
                if (isnullstartblock(got->br_startblock))
                        mval->br_startblock = DELAYSTARTBLOCK;
                return;
        }

        if (obno > *bno)
                *bno = obno;
        ASSERT((*bno >= obno) || (n == 0));
        ASSERT(*bno < end);
        mval->br_startoff = *bno;
        if (isnullstartblock(got->br_startblock))
                mval->br_startblock = DELAYSTARTBLOCK;
        else
                mval->br_startblock = got->br_startblock +
                                        (*bno - got->br_startoff);
        /*
         * Return the minimum of what we got and what we asked for for
         * the length.  We can use the len variable here because it is
         * modified below and we could have been there before coming
         * here if the first part of the allocation didn't overlap what
         * was asked for.
         */
        mval->br_blockcount = XFS_FILBLKS_MIN(end - *bno,
                        got->br_blockcount - (*bno - got->br_startoff));
        mval->br_state = got->br_state;
        ASSERT(mval->br_blockcount <= len);
        return;
}

/*
 * Update and validate the extent map to return
 */
STATIC void
xfs_bmapi_update_map(
        struct xfs_bmbt_irec    **map,
        xfs_fileoff_t           *bno,
        xfs_filblks_t           *len,
        xfs_fileoff_t           obno,
        xfs_fileoff_t           end,
        int                     *n,
        int                     flags)
{
        xfs_bmbt_irec_t *mval = *map;

        ASSERT((flags & XFS_BMAPI_ENTIRE) ||
               ((mval->br_startoff + mval->br_blockcount) <= end));
        ASSERT((flags & XFS_BMAPI_ENTIRE) || (mval->br_blockcount <= *len) ||
               (mval->br_startoff < obno));

        *bno = mval->br_startoff + mval->br_blockcount;
        *len = end - *bno;
        if (*n > 0 && mval->br_startoff == mval[-1].br_startoff) {
                /* update previous map with new information */
                ASSERT(mval->br_startblock == mval[-1].br_startblock);
                ASSERT(mval->br_blockcount > mval[-1].br_blockcount);
                ASSERT(mval->br_state == mval[-1].br_state);
                mval[-1].br_blockcount = mval->br_blockcount;
                mval[-1].br_state = mval->br_state;
        } else if (*n > 0 && mval->br_startblock != DELAYSTARTBLOCK &&
                   mval[-1].br_startblock != DELAYSTARTBLOCK &&
                   mval[-1].br_startblock != HOLESTARTBLOCK &&
                   mval->br_startblock == mval[-1].br_startblock +
                                          mval[-1].br_blockcount &&
                   ((flags & XFS_BMAPI_IGSTATE) ||
                        mval[-1].br_state == mval->br_state)) {
                ASSERT(mval->br_startoff ==
                       mval[-1].br_startoff + mval[-1].br_blockcount);
                mval[-1].br_blockcount += mval->br_blockcount;
        } else if (*n > 0 &&
                   mval->br_startblock == DELAYSTARTBLOCK &&
                   mval[-1].br_startblock == DELAYSTARTBLOCK &&
                   mval->br_startoff ==
                   mval[-1].br_startoff + mval[-1].br_blockcount) {
                mval[-1].br_blockcount += mval->br_blockcount;
                mval[-1].br_state = mval->br_state;
        } else if (!((*n == 0) &&
                     ((mval->br_startoff + mval->br_blockcount) <=
                      obno))) {
                mval++;
                (*n)++;
        }
        *map = mval;
}

/*
 * Map file blocks to filesystem blocks without allocation.
 */
int
xfs_bmapi_read(
        struct xfs_inode        *ip,
        xfs_fileoff_t           bno,
        xfs_filblks_t           len,
        struct xfs_bmbt_irec    *mval,
        int                     *nmap,
        int                     flags)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp;
        struct xfs_bmbt_irec    got;
        xfs_fileoff_t           obno;
        xfs_fileoff_t           end;
        xfs_extnum_t            idx;
        int                     error;
        bool                    eof = false;
        int                     n = 0;
        int                     whichfork = xfs_bmapi_whichfork(flags);

        ASSERT(*nmap >= 1);
        ASSERT(!(flags & ~(XFS_BMAPI_ATTRFORK|XFS_BMAPI_ENTIRE|
                           XFS_BMAPI_IGSTATE|XFS_BMAPI_COWFORK)));
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED|XFS_ILOCK_EXCL));

        if (unlikely(XFS_TEST_ERROR(
            (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
             XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
             mp, XFS_ERRTAG_BMAPIFORMAT))) {
                XFS_ERROR_REPORT("xfs_bmapi_read", XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        XFS_STATS_INC(mp, xs_blk_mapr);

        ifp = XFS_IFORK_PTR(ip, whichfork);

        /* No CoW fork?  Return a hole. */
        if (whichfork == XFS_COW_FORK && !ifp) {
                mval->br_startoff = bno;
                mval->br_startblock = HOLESTARTBLOCK;
                mval->br_blockcount = len;
                mval->br_state = XFS_EXT_NORM;
                *nmap = 1;
                return 0;
        }

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(NULL, ip, whichfork);
                if (error)
                        return error;
        }

        if (!xfs_iext_lookup_extent(ip, ifp, bno, &idx, &got))
                eof = true;
        end = bno + len;
        obno = bno;

        while (bno < end && n < *nmap) {
                /* Reading past eof, act as though there's a hole up to end. */
                if (eof)
                        got.br_startoff = end;
                if (got.br_startoff > bno) {
                        /* Reading in a hole.  */
                        mval->br_startoff = bno;
                        mval->br_startblock = HOLESTARTBLOCK;
                        mval->br_blockcount =
                                XFS_FILBLKS_MIN(len, got.br_startoff - bno);
                        mval->br_state = XFS_EXT_NORM;
                        bno += mval->br_blockcount;
                        len -= mval->br_blockcount;
                        mval++;
                        n++;
                        continue;
                }

                /* set up the extent map to return. */
                xfs_bmapi_trim_map(mval, &got, &bno, len, obno, end, n, flags);
                xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);

                /* If we're done, stop now. */
                if (bno >= end || n >= *nmap)
                        break;

                /* Else go on to the next record. */
                if (!xfs_iext_get_extent(ifp, ++idx, &got))
                        eof = true;
        }
        *nmap = n;
        return 0;
}

/*
 * Add a delayed allocation extent to an inode. Blocks are reserved from the
 * global pool and the extent inserted into the inode in-core extent tree.
 *
 * On entry, got refers to the first extent beyond the offset of the extent to
 * allocate or eof is specified if no such extent exists. On return, got refers
 * to the extent record that was inserted to the inode fork.
 *
 * Note that the allocated extent may have been merged with contiguous extents
 * during insertion into the inode fork. Thus, got does not reflect the current
 * state of the inode fork on return. If necessary, the caller can use lastx to
 * look up the updated record in the inode fork.
 */
int
xfs_bmapi_reserve_delalloc(
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_fileoff_t           off,
        xfs_filblks_t           len,
        xfs_filblks_t           prealloc,
        struct xfs_bmbt_irec    *got,
        xfs_extnum_t            *lastx,
        int                     eof)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        xfs_extlen_t            alen;
        xfs_extlen_t            indlen;
        char                    rt = XFS_IS_REALTIME_INODE(ip);
        xfs_extlen_t            extsz;
        int                     error;
        xfs_fileoff_t           aoff = off;

        /*
         * Cap the alloc length. Keep track of prealloc so we know whether to
         * tag the inode before we return.
         */
        alen = XFS_FILBLKS_MIN(len + prealloc, MAXEXTLEN);
        if (!eof)
                alen = XFS_FILBLKS_MIN(alen, got->br_startoff - aoff);
        if (prealloc && alen >= len)
                prealloc = alen - len;

        /* Figure out the extent size, adjust alen */
        if (whichfork == XFS_COW_FORK)
                extsz = xfs_get_cowextsz_hint(ip);
        else
                extsz = xfs_get_extsz_hint(ip);
        if (extsz) {
                struct xfs_bmbt_irec    prev;

                if (!xfs_iext_get_extent(ifp, *lastx - 1, &prev))
                        prev.br_startoff = NULLFILEOFF;

                error = xfs_bmap_extsize_align(mp, got, &prev, extsz, rt, eof,
                                               1, 0, &aoff, &alen);
                ASSERT(!error);
        }

        if (rt)
                extsz = alen / mp->m_sb.sb_rextsize;

        /*
         * Make a transaction-less quota reservation for delayed allocation
         * blocks.  This number gets adjusted later.  We return if we haven't
         * allocated blocks already inside this loop.
         */
        error = xfs_trans_reserve_quota_nblks(NULL, ip, (long)alen, 0,
                        rt ? XFS_QMOPT_RES_RTBLKS : XFS_QMOPT_RES_REGBLKS);
        if (error)
                return error;

        /*
         * Split changing sb for alen and indlen since they could be coming
         * from different places.
         */
        indlen = (xfs_extlen_t)xfs_bmap_worst_indlen(ip, alen);
        ASSERT(indlen > 0);

        if (rt) {
                error = xfs_mod_frextents(mp, -((int64_t)extsz));
        } else {
                error = xfs_mod_fdblocks(mp, -((int64_t)alen), false);
        }

        if (error)
                goto out_unreserve_quota;

        error = xfs_mod_fdblocks(mp, -((int64_t)indlen), false);
        if (error)
                goto out_unreserve_blocks;


        ip->i_delayed_blks += alen;

        got->br_startoff = aoff;
        got->br_startblock = nullstartblock(indlen);
        got->br_blockcount = alen;
        got->br_state = XFS_EXT_NORM;

        xfs_bmap_add_extent_hole_delay(ip, whichfork, lastx, got);

        /*
         * Tag the inode if blocks were preallocated. Note that COW fork
         * preallocation can occur at the start or end of the extent, even when
         * prealloc == 0, so we must also check the aligned offset and length.
         */
        if (whichfork == XFS_DATA_FORK && prealloc)
                xfs_inode_set_eofblocks_tag(ip);
        if (whichfork == XFS_COW_FORK && (prealloc || aoff < off || alen > len))
                xfs_inode_set_cowblocks_tag(ip);

        return 0;

out_unreserve_blocks:
        if (rt)
                xfs_mod_frextents(mp, extsz);
        else
                xfs_mod_fdblocks(mp, alen, false);
out_unreserve_quota:
        if (XFS_IS_QUOTA_ON(mp))
                xfs_trans_unreserve_quota_nblks(NULL, ip, (long)alen, 0, rt ?
                                XFS_QMOPT_RES_RTBLKS : XFS_QMOPT_RES_REGBLKS);
        return error;
}

static int
xfs_bmapi_allocate(
        struct xfs_bmalloca     *bma)
{
        struct xfs_mount        *mp = bma->ip->i_mount;
        int                     whichfork = xfs_bmapi_whichfork(bma->flags);
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(bma->ip, whichfork);
        int                     tmp_logflags = 0;
        int                     error;

        ASSERT(bma->length > 0);

        /*
         * For the wasdelay case, we could also just allocate the stuff asked
         * for in this bmap call but that wouldn't be as good.
         */
        if (bma->wasdel) {
                bma->length = (xfs_extlen_t)bma->got.br_blockcount;
                bma->offset = bma->got.br_startoff;
                if (bma->idx)
                        xfs_iext_get_extent(ifp, bma->idx - 1, &bma->prev);
        } else {
                bma->length = XFS_FILBLKS_MIN(bma->length, MAXEXTLEN);
                if (!bma->eof)
                        bma->length = XFS_FILBLKS_MIN(bma->length,
                                        bma->got.br_startoff - bma->offset);
        }

        /*
         * Set the data type being allocated. For the data fork, the first data
         * in the file is treated differently to all other allocations. For the
         * attribute fork, we only need to ensure the allocated range is not on
         * the busy list.
         */
        if (!(bma->flags & XFS_BMAPI_METADATA)) {
                bma->datatype = XFS_ALLOC_NOBUSY;
                if (whichfork == XFS_DATA_FORK) {
                        if (bma->offset == 0)
                                bma->datatype |= XFS_ALLOC_INITIAL_USER_DATA;
                        else
                                bma->datatype |= XFS_ALLOC_USERDATA;
                }
                if (bma->flags & XFS_BMAPI_ZERO)
                        bma->datatype |= XFS_ALLOC_USERDATA_ZERO;
        }

        bma->minlen = (bma->flags & XFS_BMAPI_CONTIG) ? bma->length : 1;

        /*
         * Only want to do the alignment at the eof if it is userdata and
         * allocation length is larger than a stripe unit.
         */
        if (mp->m_dalign && bma->length >= mp->m_dalign &&
            !(bma->flags & XFS_BMAPI_METADATA) && whichfork == XFS_DATA_FORK) {
                error = xfs_bmap_isaeof(bma, whichfork);
                if (error)
                        return error;
        }

        error = xfs_bmap_alloc(bma);
        if (error)
                return error;

        if (bma->cur)
                bma->cur->bc_private.b.firstblock = *bma->firstblock;
        if (bma->blkno == NULLFSBLOCK)
                return 0;
        if ((ifp->if_flags & XFS_IFBROOT) && !bma->cur) {
                bma->cur = xfs_bmbt_init_cursor(mp, bma->tp, bma->ip, whichfork);
                bma->cur->bc_private.b.firstblock = *bma->firstblock;
                bma->cur->bc_private.b.dfops = bma->dfops;
        }
        /*
         * Bump the number of extents we've allocated
         * in this call.
         */
        bma->nallocs++;

        if (bma->cur)
                bma->cur->bc_private.b.flags =
                        bma->wasdel ? XFS_BTCUR_BPRV_WASDEL : 0;

        bma->got.br_startoff = bma->offset;
        bma->got.br_startblock = bma->blkno;
        bma->got.br_blockcount = bma->length;
        bma->got.br_state = XFS_EXT_NORM;

        /*
         * In the data fork, a wasdelay extent has been initialized, so
         * shouldn't be flagged as unwritten.
         *
         * For the cow fork, however, we convert delalloc reservations
         * (extents allocated for speculative preallocation) to
         * allocated unwritten extents, and only convert the unwritten
         * extents to real extents when we're about to write the data.
         */
        if ((!bma->wasdel || (bma->flags & XFS_BMAPI_COWFORK)) &&
            (bma->flags & XFS_BMAPI_PREALLOC) &&
            xfs_sb_version_hasextflgbit(&mp->m_sb))
                bma->got.br_state = XFS_EXT_UNWRITTEN;

        if (bma->wasdel)
                error = xfs_bmap_add_extent_delay_real(bma, whichfork);
        else
                error = xfs_bmap_add_extent_hole_real(bma->tp, bma->ip,
                                whichfork, &bma->idx, &bma->cur, &bma->got,
                                bma->firstblock, bma->dfops, &bma->logflags);

        bma->logflags |= tmp_logflags;
        if (error)
                return error;

        /*
         * Update our extent pointer, given that xfs_bmap_add_extent_delay_real
         * or xfs_bmap_add_extent_hole_real might have merged it into one of
         * the neighbouring ones.
         */
        xfs_iext_get_extent(ifp, bma->idx, &bma->got);

        ASSERT(bma->got.br_startoff <= bma->offset);
        ASSERT(bma->got.br_startoff + bma->got.br_blockcount >=
               bma->offset + bma->length);
        ASSERT(bma->got.br_state == XFS_EXT_NORM ||
               bma->got.br_state == XFS_EXT_UNWRITTEN);
        return 0;
}

STATIC int
xfs_bmapi_convert_unwritten(
        struct xfs_bmalloca     *bma,
        struct xfs_bmbt_irec    *mval,
        xfs_filblks_t           len,
        int                     flags)
{
        int                     whichfork = xfs_bmapi_whichfork(flags);
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(bma->ip, whichfork);
        int                     tmp_logflags = 0;
        int                     error;

        /* check if we need to do unwritten->real conversion */
        if (mval->br_state == XFS_EXT_UNWRITTEN &&
            (flags & XFS_BMAPI_PREALLOC))
                return 0;

        /* check if we need to do real->unwritten conversion */
        if (mval->br_state == XFS_EXT_NORM &&
            (flags & (XFS_BMAPI_PREALLOC | XFS_BMAPI_CONVERT)) !=
                        (XFS_BMAPI_PREALLOC | XFS_BMAPI_CONVERT))
                return 0;

        /*
         * Modify (by adding) the state flag, if writing.
         */
        ASSERT(mval->br_blockcount <= len);
        if ((ifp->if_flags & XFS_IFBROOT) && !bma->cur) {
                bma->cur = xfs_bmbt_init_cursor(bma->ip->i_mount, bma->tp,
                                        bma->ip, whichfork);
                bma->cur->bc_private.b.firstblock = *bma->firstblock;
                bma->cur->bc_private.b.dfops = bma->dfops;
        }
        mval->br_state = (mval->br_state == XFS_EXT_UNWRITTEN)
                                ? XFS_EXT_NORM : XFS_EXT_UNWRITTEN;

        /*
         * Before insertion into the bmbt, zero the range being converted
         * if required.
         */
        if (flags & XFS_BMAPI_ZERO) {
                error = xfs_zero_extent(bma->ip, mval->br_startblock,
                                        mval->br_blockcount);
                if (error)
                        return error;
        }

        error = xfs_bmap_add_extent_unwritten_real(bma->tp, bma->ip, whichfork,
                        &bma->idx, &bma->cur, mval, bma->firstblock, bma->dfops,
                        &tmp_logflags);
        /*
         * Log the inode core unconditionally in the unwritten extent conversion
         * path because the conversion might not have done so (e.g., if the
         * extent count hasn't changed). We need to make sure the inode is dirty
         * in the transaction for the sake of fsync(), even if nothing has
         * changed, because fsync() will not force the log for this transaction
         * unless it sees the inode pinned.
         *
         * Note: If we're only converting cow fork extents, there aren't
         * any on-disk updates to make, so we don't need to log anything.
         */
        if (whichfork != XFS_COW_FORK)
                bma->logflags |= tmp_logflags | XFS_ILOG_CORE;
        if (error)
                return error;

        /*
         * Update our extent pointer, given that
         * xfs_bmap_add_extent_unwritten_real might have merged it into one
         * of the neighbouring ones.
         */
        xfs_iext_get_extent(ifp, bma->idx, &bma->got);

        /*
         * We may have combined previously unwritten space with written space,
         * so generate another request.
         */
        if (mval->br_blockcount < len)
                return -EAGAIN;
        return 0;
}

/*
 * Map file blocks to filesystem blocks, and allocate blocks or convert the
 * extent state if necessary.  Details behaviour is controlled by the flags
 * parameter.  Only allocates blocks from a single allocation group, to avoid
 * locking problems.
 *
 * The returned value in "firstblock" from the first call in a transaction
 * must be remembered and presented to subsequent calls in "firstblock".
 * An upper bound for the number of blocks to be allocated is supplied to
 * the first call in "total"; if no allocation group has that many free
 * blocks then the call will fail (return NULLFSBLOCK in "firstblock").
 */
int
xfs_bmapi_write(
        struct xfs_trans        *tp,            /* transaction pointer */
        struct xfs_inode        *ip,            /* incore inode */
        xfs_fileoff_t           bno,            /* starting file offs. mapped */
        xfs_filblks_t           len,            /* length to map in file */
        int                     flags,          /* XFS_BMAPI_... */
        xfs_fsblock_t           *firstblock,    /* first allocated block
                                                   controls a.g. for allocs */
        xfs_extlen_t            total,          /* total blocks needed */
        struct xfs_bmbt_irec    *mval,          /* output: map values */
        int                     *nmap,          /* i/o: mval size/count */
        struct xfs_defer_ops    *dfops)         /* i/o: list extents to free */
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp;
        struct xfs_bmalloca     bma = { NULL }; /* args for xfs_bmap_alloc */
        xfs_fileoff_t           end;            /* end of mapped file region */
        bool                    eof = false;    /* after the end of extents */
        int                     error;          /* error return */
        int                     n;              /* current extent index */
        xfs_fileoff_t           obno;           /* old block number (offset) */
        int                     whichfork;      /* data or attr fork */

#ifdef DEBUG
        xfs_fileoff_t           orig_bno;       /* original block number value */
        int                     orig_flags;     /* original flags arg value */
        xfs_filblks_t           orig_len;       /* original value of len arg */
        struct xfs_bmbt_irec    *orig_mval;     /* original value of mval */
        int                     orig_nmap;      /* original value of *nmap */

        orig_bno = bno;
        orig_len = len;
        orig_flags = flags;
        orig_mval = mval;
        orig_nmap = *nmap;
#endif
        whichfork = xfs_bmapi_whichfork(flags);

        ASSERT(*nmap >= 1);
        ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);
        ASSERT(!(flags & XFS_BMAPI_IGSTATE));
        ASSERT(tp != NULL ||
               (flags & (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK)) ==
                        (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK));
        ASSERT(len > 0);
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_LOCAL);
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(!(flags & XFS_BMAPI_REMAP));

        /* zeroing is for currently only for data extents, not metadata */
        ASSERT((flags & (XFS_BMAPI_METADATA | XFS_BMAPI_ZERO)) !=
                        (XFS_BMAPI_METADATA | XFS_BMAPI_ZERO));
        /*
         * we can allocate unwritten extents or pre-zero allocated blocks,
         * but it makes no sense to do both at once. This would result in
         * zeroing the unwritten extent twice, but it still being an
         * unwritten extent....
         */
        ASSERT((flags & (XFS_BMAPI_PREALLOC | XFS_BMAPI_ZERO)) !=
                        (XFS_BMAPI_PREALLOC | XFS_BMAPI_ZERO));

        if (unlikely(XFS_TEST_ERROR(
            (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
             XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
             mp, XFS_ERRTAG_BMAPIFORMAT))) {
                XFS_ERROR_REPORT("xfs_bmapi_write", XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        ifp = XFS_IFORK_PTR(ip, whichfork);

        XFS_STATS_INC(mp, xs_blk_mapw);

        if (*firstblock == NULLFSBLOCK) {
                if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE)
                        bma.minleft = be16_to_cpu(ifp->if_broot->bb_level) + 1;
                else
                        bma.minleft = 1;
        } else {
                bma.minleft = 0;
        }

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(tp, ip, whichfork);
                if (error)
                        goto error0;
        }

        n = 0;
        end = bno + len;
        obno = bno;

        if (!xfs_iext_lookup_extent(ip, ifp, bno, &bma.idx, &bma.got))
                eof = true;
        if (!xfs_iext_get_extent(ifp, bma.idx - 1, &bma.prev))
                bma.prev.br_startoff = NULLFILEOFF;
        bma.tp = tp;
        bma.ip = ip;
        bma.total = total;
        bma.datatype = 0;
        bma.dfops = dfops;
        bma.firstblock = firstblock;

        while (bno < end && n < *nmap) {
                bool                    need_alloc = false, wasdelay = false;

                /* in hole or beyoned EOF? */
                if (eof || bma.got.br_startoff > bno) {
                        if (flags & XFS_BMAPI_DELALLOC) {
                                /*
                                 * For the COW fork we can reasonably get a
                                 * request for converting an extent that races
                                 * with other threads already having converted
                                 * part of it, as there converting COW to
                                 * regular blocks is not protected using the
                                 * IOLOCK.
                                 */
                                ASSERT(flags & XFS_BMAPI_COWFORK);
                                if (!(flags & XFS_BMAPI_COWFORK)) {
                                        error = -EIO;
                                        goto error0;
                                }

                                if (eof || bno >= end)
                                        break;
                        } else {
                                need_alloc = true;
                        }
                } else if (isnullstartblock(bma.got.br_startblock)) {
                        wasdelay = true;
                }

                /*
                 * First, deal with the hole before the allocated space
                 * that we found, if any.
                 */
                if (need_alloc || wasdelay) {
                        bma.eof = eof;
                        bma.conv = !!(flags & XFS_BMAPI_CONVERT);
                        bma.wasdel = wasdelay;
                        bma.offset = bno;
                        bma.flags = flags;

                        /*
                         * There's a 32/64 bit type mismatch between the
                         * allocation length request (which can be 64 bits in
                         * length) and the bma length request, which is
                         * xfs_extlen_t and therefore 32 bits. Hence we have to
                         * check for 32-bit overflows and handle them here.
                         */
                        if (len > (xfs_filblks_t)MAXEXTLEN)
                                bma.length = MAXEXTLEN;
                        else
                                bma.length = len;

                        ASSERT(len > 0);
                        ASSERT(bma.length > 0);
                        error = xfs_bmapi_allocate(&bma);
                        if (error)
                                goto error0;
                        if (bma.blkno == NULLFSBLOCK)
                                break;

                        /*
                         * If this is a CoW allocation, record the data in
                         * the refcount btree for orphan recovery.
                         */
                        if (whichfork == XFS_COW_FORK) {
                                error = xfs_refcount_alloc_cow_extent(mp, dfops,
                                                bma.blkno, bma.length);
                                if (error)
                                        goto error0;
                        }
                }

                /* Deal with the allocated space we found.  */
                xfs_bmapi_trim_map(mval, &bma.got, &bno, len, obno,
                                                        end, n, flags);

                /* Execute unwritten extent conversion if necessary */
                error = xfs_bmapi_convert_unwritten(&bma, mval, len, flags);
                if (error == -EAGAIN)
                        continue;
                if (error)
                        goto error0;

                /* update the extent map to return */
                xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);

                /*
                 * If we're done, stop now.  Stop when we've allocated
                 * XFS_BMAP_MAX_NMAP extents no matter what.  Otherwise
                 * the transaction may get too big.
                 */
                if (bno >= end || n >= *nmap || bma.nallocs >= *nmap)
                        break;

                /* Else go on to the next record. */
                bma.prev = bma.got;
                if (!xfs_iext_get_extent(ifp, ++bma.idx, &bma.got))
                        eof = true;
        }
        *nmap = n;

        /*
         * Transform from btree to extents, give it cur.
         */
        if (xfs_bmap_wants_extents(ip, whichfork)) {
                int             tmp_logflags = 0;

                ASSERT(bma.cur);
                error = xfs_bmap_btree_to_extents(tp, ip, bma.cur,
                        &tmp_logflags, whichfork);
                bma.logflags |= tmp_logflags;
                if (error)
                        goto error0;
        }

        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE ||
               XFS_IFORK_NEXTENTS(ip, whichfork) >
                XFS_IFORK_MAXEXT(ip, whichfork));
        error = 0;
error0:
        /*
         * Log everything.  Do this after conversion, there's no point in
         * logging the extent records if we've converted to btree format.
         */
        if ((bma.logflags & xfs_ilog_fext(whichfork)) &&
            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS)
                bma.logflags &= ~xfs_ilog_fext(whichfork);
        else if ((bma.logflags & xfs_ilog_fbroot(whichfork)) &&
                 XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE)
                bma.logflags &= ~xfs_ilog_fbroot(whichfork);
        /*
         * Log whatever the flags say, even if error.  Otherwise we might miss
         * detecting a case where the data is changed, there's an error,
         * and it's not logged so we don't shutdown when we should.
         */
        if (bma.logflags)
                xfs_trans_log_inode(tp, ip, bma.logflags);

        if (bma.cur) {
                if (!error) {
                        ASSERT(*firstblock == NULLFSBLOCK ||
                               XFS_FSB_TO_AGNO(mp, *firstblock) <=
                               XFS_FSB_TO_AGNO(mp,
                                       bma.cur->bc_private.b.firstblock));
                        *firstblock = bma.cur->bc_private.b.firstblock;
                }
                xfs_btree_del_cursor(bma.cur,
                        error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        }
        if (!error)
                xfs_bmap_validate_ret(orig_bno, orig_len, orig_flags, orig_mval,
                        orig_nmap, *nmap);
        return error;
}

static int
xfs_bmapi_remap(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        xfs_fileoff_t           bno,
        xfs_filblks_t           len,
        xfs_fsblock_t           startblock,
        struct xfs_defer_ops    *dfops)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
        struct xfs_btree_cur    *cur = NULL;
        xfs_fsblock_t           firstblock = NULLFSBLOCK;
        struct xfs_bmbt_irec    got;
        xfs_extnum_t            idx;
        int                     logflags = 0, error;

        ASSERT(len > 0);
        ASSERT(len <= (xfs_filblks_t)MAXEXTLEN);
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        if (unlikely(XFS_TEST_ERROR(
            (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
             XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
             mp, XFS_ERRTAG_BMAPIFORMAT))) {
                XFS_ERROR_REPORT("xfs_bmapi_remap", XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
                if (error)
                        return error;
        }

        if (xfs_iext_lookup_extent(ip, ifp, bno, &idx, &got)) {
                /* make sure we only reflink into a hole. */
                ASSERT(got.br_startoff > bno);
                ASSERT(got.br_startoff - bno >= len);
        }

        ip->i_d.di_nblocks += len;
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        if (ifp->if_flags & XFS_IFBROOT) {
                cur = xfs_bmbt_init_cursor(mp, tp, ip, XFS_DATA_FORK);
                cur->bc_private.b.firstblock = firstblock;
                cur->bc_private.b.dfops = dfops;
                cur->bc_private.b.flags = 0;
        }

        got.br_startoff = bno;
        got.br_startblock = startblock;
        got.br_blockcount = len;
        got.br_state = XFS_EXT_NORM;

        error = xfs_bmap_add_extent_hole_real(tp, ip, XFS_DATA_FORK, &idx, &cur,
                        &got, &firstblock, dfops, &logflags);
        if (error)
                goto error0;

        if (xfs_bmap_wants_extents(ip, XFS_DATA_FORK)) {
                int             tmp_logflags = 0;

                error = xfs_bmap_btree_to_extents(tp, ip, cur,
                        &tmp_logflags, XFS_DATA_FORK);
                logflags |= tmp_logflags;
        }

error0:
        if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS)
                logflags &= ~XFS_ILOG_DEXT;
        else if (ip->i_d.di_format != XFS_DINODE_FMT_BTREE)
                logflags &= ~XFS_ILOG_DBROOT;

        if (logflags)
                xfs_trans_log_inode(tp, ip, logflags);
        if (cur) {
                xfs_btree_del_cursor(cur,
                                error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        }
        return error;
}

/*
 * When a delalloc extent is split (e.g., due to a hole punch), the original
 * indlen reservation must be shared across the two new extents that are left
 * behind.
 *
 * Given the original reservation and the worst case indlen for the two new
 * extents (as calculated by xfs_bmap_worst_indlen()), split the original
 * reservation fairly across the two new extents. If necessary, steal available
 * blocks from a deleted extent to make up a reservation deficiency (e.g., if
 * ores == 1). The number of stolen blocks is returned. The availability and
 * subsequent accounting of stolen blocks is the responsibility of the caller.
 */
static xfs_filblks_t
xfs_bmap_split_indlen(
        xfs_filblks_t                   ores,           /* original res. */
        xfs_filblks_t                   *indlen1,       /* ext1 worst indlen */
        xfs_filblks_t                   *indlen2,       /* ext2 worst indlen */
        xfs_filblks_t                   avail)          /* stealable blocks */
{
        xfs_filblks_t                   len1 = *indlen1;
        xfs_filblks_t                   len2 = *indlen2;
        xfs_filblks_t                   nres = len1 + len2; /* new total res. */
        xfs_filblks_t                   stolen = 0;
        xfs_filblks_t                   resfactor;

        /*
         * Steal as many blocks as we can to try and satisfy the worst case
         * indlen for both new extents.
         */
        if (ores < nres && avail)
                stolen = XFS_FILBLKS_MIN(nres - ores, avail);
        ores += stolen;

         /* nothing else to do if we've satisfied the new reservation */
        if (ores >= nres)
                return stolen;

        /*
         * We can't meet the total required reservation for the two extents.
         * Calculate the percent of the overall shortage between both extents
         * and apply this percentage to each of the requested indlen values.
         * This distributes the shortage fairly and reduces the chances that one
         * of the two extents is left with nothing when extents are repeatedly
         * split.
         */
        resfactor = (ores * 100);
        do_div(resfactor, nres);
        len1 *= resfactor;
        do_div(len1, 100);
        len2 *= resfactor;
        do_div(len2, 100);
        ASSERT(len1 + len2 <= ores);
        ASSERT(len1 < *indlen1 && len2 < *indlen2);

        /*
         * Hand out the remainder to each extent. If one of the two reservations
         * is zero, we want to make sure that one gets a block first. The loop
         * below starts with len1, so hand len2 a block right off the bat if it
         * is zero.
         */
        ores -= (len1 + len2);
        ASSERT((*indlen1 - len1) + (*indlen2 - len2) >= ores);
        if (ores && !len2 && *indlen2) {
                len2++;
                ores--;
        }
        while (ores) {
                if (len1 < *indlen1) {
                        len1++;
                        ores--;
                }
                if (!ores)
                        break;
                if (len2 < *indlen2) {
                        len2++;
                        ores--;
                }
        }

        *indlen1 = len1;
        *indlen2 = len2;

        return stolen;
}

int
xfs_bmap_del_extent_delay(
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_extnum_t            *idx,
        struct xfs_bmbt_irec    *got,
        struct xfs_bmbt_irec    *del)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_bmbt_irec    new;
        int64_t                 da_old, da_new, da_diff = 0;
        xfs_fileoff_t           del_endoff, got_endoff;
        xfs_filblks_t           got_indlen, new_indlen, stolen;
        int                     state = xfs_bmap_fork_to_state(whichfork);
        int                     error = 0;
        bool                    isrt;

        XFS_STATS_INC(mp, xs_del_exlist);

        isrt = (whichfork == XFS_DATA_FORK) && XFS_IS_REALTIME_INODE(ip);
        del_endoff = del->br_startoff + del->br_blockcount;
        got_endoff = got->br_startoff + got->br_blockcount;
        da_old = startblockval(got->br_startblock);
        da_new = 0;

        ASSERT(*idx >= 0);
        ASSERT(*idx <= xfs_iext_count(ifp));
        ASSERT(del->br_blockcount > 0);
        ASSERT(got->br_startoff <= del->br_startoff);
        ASSERT(got_endoff >= del_endoff);

        if (isrt) {
                uint64_t rtexts = XFS_FSB_TO_B(mp, del->br_blockcount);

                do_div(rtexts, mp->m_sb.sb_rextsize);
                xfs_mod_frextents(mp, rtexts);
        }

        /*
         * Update the inode delalloc counter now and wait to update the
         * sb counters as we might have to borrow some blocks for the
         * indirect block accounting.
         */
        error = xfs_trans_reserve_quota_nblks(NULL, ip,
                        -((long)del->br_blockcount), 0,
                        isrt ? XFS_QMOPT_RES_RTBLKS : XFS_QMOPT_RES_REGBLKS);
        if (error)
                return error;
        ip->i_delayed_blks -= del->br_blockcount;

        if (got->br_startoff == del->br_startoff)
                state |= BMAP_LEFT_FILLING;
        if (got_endoff == del_endoff)
                state |= BMAP_RIGHT_FILLING;

        switch (state & (BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING)) {
        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING:
                /*
                 * Matches the whole extent.  Delete the entry.
                 */
                xfs_iext_remove(ip, *idx, 1, state);
                --*idx;
                break;
        case BMAP_LEFT_FILLING:
                /*
                 * Deleting the first part of the extent.
                 */
                got->br_startoff = del_endoff;
                got->br_blockcount -= del->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip,
                                got->br_blockcount), da_old);
                got->br_startblock = nullstartblock((int)da_new);
                xfs_iext_update_extent(ip, state, *idx, got);
                break;
        case BMAP_RIGHT_FILLING:
                /*
                 * Deleting the last part of the extent.
                 */
                got->br_blockcount = got->br_blockcount - del->br_blockcount;
                da_new = XFS_FILBLKS_MIN(xfs_bmap_worst_indlen(ip,
                                got->br_blockcount), da_old);
                got->br_startblock = nullstartblock((int)da_new);
                xfs_iext_update_extent(ip, state, *idx, got);
                break;
        case 0:
                /*
                 * Deleting the middle of the extent.
                 *
                 * Distribute the original indlen reservation across the two new
                 * extents.  Steal blocks from the deleted extent if necessary.
                 * Stealing blocks simply fudges the fdblocks accounting below.
                 * Warn if either of the new indlen reservations is zero as this
                 * can lead to delalloc problems.
                 */
                got->br_blockcount = del->br_startoff - got->br_startoff;
                got_indlen = xfs_bmap_worst_indlen(ip, got->br_blockcount);

                new.br_blockcount = got_endoff - del_endoff;
                new_indlen = xfs_bmap_worst_indlen(ip, new.br_blockcount);

                WARN_ON_ONCE(!got_indlen || !new_indlen);
                stolen = xfs_bmap_split_indlen(da_old, &got_indlen, &new_indlen,
                                                       del->br_blockcount);

                got->br_startblock = nullstartblock((int)got_indlen);
                xfs_iext_update_extent(ip, state, *idx, got);

                new.br_startoff = del_endoff;
                new.br_state = got->br_state;
                new.br_startblock = nullstartblock((int)new_indlen);

                ++*idx;
                xfs_iext_insert(ip, *idx, 1, &new, state);

                da_new = got_indlen + new_indlen - stolen;
                del->br_blockcount -= stolen;
                break;
        }

        ASSERT(da_old >= da_new);
        da_diff = da_old - da_new;
        if (!isrt)
                da_diff += del->br_blockcount;
        if (da_diff)
                xfs_mod_fdblocks(mp, da_diff, false);
        return error;
}

void
xfs_bmap_del_extent_cow(
        struct xfs_inode        *ip,
        xfs_extnum_t            *idx,
        struct xfs_bmbt_irec    *got,
        struct xfs_bmbt_irec    *del)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
        struct xfs_bmbt_irec    new;
        xfs_fileoff_t           del_endoff, got_endoff;
        int                     state = BMAP_COWFORK;

        XFS_STATS_INC(mp, xs_del_exlist);

        del_endoff = del->br_startoff + del->br_blockcount;
        got_endoff = got->br_startoff + got->br_blockcount;

        ASSERT(*idx >= 0);
        ASSERT(*idx <= xfs_iext_count(ifp));
        ASSERT(del->br_blockcount > 0);
        ASSERT(got->br_startoff <= del->br_startoff);
        ASSERT(got_endoff >= del_endoff);
        ASSERT(!isnullstartblock(got->br_startblock));

        if (got->br_startoff == del->br_startoff)
                state |= BMAP_LEFT_FILLING;
        if (got_endoff == del_endoff)
                state |= BMAP_RIGHT_FILLING;

        switch (state & (BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING)) {
        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING:
                /*
                 * Matches the whole extent.  Delete the entry.
                 */
                xfs_iext_remove(ip, *idx, 1, state);
                --*idx;
                break;
        case BMAP_LEFT_FILLING:
                /*
                 * Deleting the first part of the extent.
                 */
                got->br_startoff = del_endoff;
                got->br_blockcount -= del->br_blockcount;
                got->br_startblock = del->br_startblock + del->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, got);
                break;
        case BMAP_RIGHT_FILLING:
                /*
                 * Deleting the last part of the extent.
                 */
                got->br_blockcount -= del->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, got);
                break;
        case 0:
                /*
                 * Deleting the middle of the extent.
                 */
                got->br_blockcount = del->br_startoff - got->br_startoff;
                xfs_iext_update_extent(ip, state, *idx, got);

                new.br_startoff = del_endoff;
                new.br_blockcount = got_endoff - del_endoff;
                new.br_state = got->br_state;
                new.br_startblock = del->br_startblock + del->br_blockcount;

                ++*idx;
                xfs_iext_insert(ip, *idx, 1, &new, state);
                break;
        }
}

/*
 * Called by xfs_bmapi to update file extent records and the btree
 * after removing space.
 */
STATIC int                              /* error */
xfs_bmap_del_extent_real(
        xfs_inode_t             *ip,    /* incore inode pointer */
        xfs_trans_t             *tp,    /* current transaction pointer */
        xfs_extnum_t            *idx,   /* extent number to update/delete */
        struct xfs_defer_ops    *dfops, /* list of extents to be freed */
        xfs_btree_cur_t         *cur,   /* if null, not a btree */
        xfs_bmbt_irec_t         *del,   /* data to remove from extents */
        int                     *logflagsp, /* inode logging flags */
        int                     whichfork, /* data or attr fork */
        int                     bflags) /* bmapi flags */
{
        xfs_fsblock_t           del_endblock=0; /* first block past del */
        xfs_fileoff_t           del_endoff;     /* first offset past del */
        int                     do_fx;  /* free extent at end of routine */
        int                     error;  /* error return value */
        int                     flags = 0;/* inode logging flags */
        struct xfs_bmbt_irec    got;    /* current extent entry */
        xfs_fileoff_t           got_endoff;     /* first offset past got */
        int                     i;      /* temp state */
        xfs_ifork_t             *ifp;   /* inode fork pointer */
        xfs_mount_t             *mp;    /* mount structure */
        xfs_filblks_t           nblks;  /* quota/sb block count */
        xfs_bmbt_irec_t         new;    /* new record to be inserted */
        /* REFERENCED */
        uint                    qfield; /* quota field to update */
        int                     state = xfs_bmap_fork_to_state(whichfork);
        struct xfs_bmbt_irec    old;

        mp = ip->i_mount;
        XFS_STATS_INC(mp, xs_del_exlist);

        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT((*idx >= 0) && (*idx < xfs_iext_count(ifp)));
        ASSERT(del->br_blockcount > 0);
        xfs_iext_get_extent(ifp, *idx, &got);
        ASSERT(got.br_startoff <= del->br_startoff);
        del_endoff = del->br_startoff + del->br_blockcount;
        got_endoff = got.br_startoff + got.br_blockcount;
        ASSERT(got_endoff >= del_endoff);
        ASSERT(!isnullstartblock(got.br_startblock));
        qfield = 0;
        error = 0;

        /*
         * If it's the case where the directory code is running with no block
         * reservation, and the deleted block is in the middle of its extent,
         * and the resulting insert of an extent would cause transformation to
         * btree format, then reject it.  The calling code will then swap blocks
         * around instead.  We have to do this now, rather than waiting for the
         * conversion to btree format, since the transaction will be dirty then.
         */
        if (tp->t_blk_res == 0 &&
            XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS &&
            XFS_IFORK_NEXTENTS(ip, whichfork) >=
                        XFS_IFORK_MAXEXT(ip, whichfork) &&
            del->br_startoff > got.br_startoff && del_endoff < got_endoff)
                return -ENOSPC;

        flags = XFS_ILOG_CORE;
        if (whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip)) {
                xfs_fsblock_t   bno;
                xfs_filblks_t   len;

                ASSERT(do_mod(del->br_blockcount, mp->m_sb.sb_rextsize) == 0);
                ASSERT(do_mod(del->br_startblock, mp->m_sb.sb_rextsize) == 0);
                bno = del->br_startblock;
                len = del->br_blockcount;
                do_div(bno, mp->m_sb.sb_rextsize);
                do_div(len, mp->m_sb.sb_rextsize);
                error = xfs_rtfree_extent(tp, bno, (xfs_extlen_t)len);
                if (error)
                        goto done;
                do_fx = 0;
                nblks = len * mp->m_sb.sb_rextsize;
                qfield = XFS_TRANS_DQ_RTBCOUNT;
        } else {
                do_fx = 1;
                nblks = del->br_blockcount;
                qfield = XFS_TRANS_DQ_BCOUNT;
        }

        del_endblock = del->br_startblock + del->br_blockcount;
        if (cur) {
                error = xfs_bmbt_lookup_eq(cur, &got, &i);
                if (error)
                        goto done;
                XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
        }

        if (got.br_startoff == del->br_startoff)
                state |= BMAP_LEFT_FILLING;
        if (got_endoff == del_endoff)
                state |= BMAP_RIGHT_FILLING;

        switch (state & (BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING)) {
        case BMAP_LEFT_FILLING | BMAP_RIGHT_FILLING:
                /*
                 * Matches the whole extent.  Delete the entry.
                 */
                xfs_iext_remove(ip, *idx, 1, state);
                --*idx;

                XFS_IFORK_NEXT_SET(ip, whichfork,
                        XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
                flags |= XFS_ILOG_CORE;
                if (!cur) {
                        flags |= xfs_ilog_fext(whichfork);
                        break;
                }
                if ((error = xfs_btree_delete(cur, &i)))
                        goto done;
                XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                break;
        case BMAP_LEFT_FILLING:
                /*
                 * Deleting the first part of the extent.
                 */
                got.br_startoff = del_endoff;
                got.br_startblock = del_endblock;
                got.br_blockcount -= del->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &got);
                if (!cur) {
                        flags |= xfs_ilog_fext(whichfork);
                        break;
                }
                error = xfs_bmbt_update(cur, &got);
                if (error)
                        goto done;
                break;
        case BMAP_RIGHT_FILLING:
                /*
                 * Deleting the last part of the extent.
                 */
                got.br_blockcount -= del->br_blockcount;
                xfs_iext_update_extent(ip, state, *idx, &got);
                if (!cur) {
                        flags |= xfs_ilog_fext(whichfork);
                        break;
                }
                error = xfs_bmbt_update(cur, &got);
                if (error)
                        goto done;
                break;
        case 0:
                /*
                 * Deleting the middle of the extent.
                 */
                old = got;

                got.br_blockcount = del->br_startoff - got.br_startoff;
                xfs_iext_update_extent(ip, state, *idx, &got);

                new.br_startoff = del_endoff;
                new.br_blockcount = got_endoff - del_endoff;
                new.br_state = got.br_state;
                new.br_startblock = del_endblock;

                flags |= XFS_ILOG_CORE;
                if (cur) {
                        error = xfs_bmbt_update(cur, &got);
                        if (error)
                                goto done;
                        error = xfs_btree_increment(cur, 0, &i);
                        if (error)
                                goto done;
                        cur->bc_rec.b = new;
                        error = xfs_btree_insert(cur, &i);
                        if (error && error != -ENOSPC)
                                goto done;
                        /*
                         * If get no-space back from btree insert, it tried a
                         * split, and we have a zero block reservation.  Fix up
                         * our state and return the error.
                         */
                        if (error == -ENOSPC) {
                                /*
                                 * Reset the cursor, don't trust it after any
                                 * insert operation.
                                 */
                                error = xfs_bmbt_lookup_eq(cur, &got, &i);
                                if (error)
                                        goto done;
                                XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                                /*
                                 * Update the btree record back
                                 * to the original value.
                                 */
                                error = xfs_bmbt_update(cur, &old);
                                if (error)
                                        goto done;
                                /*
                                 * Reset the extent record back
                                 * to the original value.
                                 */
                                xfs_iext_update_extent(ip, state, *idx, &old);
                                flags = 0;
                                error = -ENOSPC;
                                goto done;
                        }
                        XFS_WANT_CORRUPTED_GOTO(mp, i == 1, done);
                } else
                        flags |= xfs_ilog_fext(whichfork);
                XFS_IFORK_NEXT_SET(ip, whichfork,
                        XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
                xfs_iext_insert(ip, *idx + 1, 1, &new, state);
                ++*idx;
                break;
        }

        /* remove reverse mapping */
        error = xfs_rmap_unmap_extent(mp, dfops, ip, whichfork, del);
        if (error)
                goto done;

        /*
         * If we need to, add to list of extents to delete.
         */
        if (do_fx && !(bflags & XFS_BMAPI_REMAP)) {
                if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK) {
                        error = xfs_refcount_decrease_extent(mp, dfops, del);
                        if (error)
                                goto done;
                } else
                        xfs_bmap_add_free(mp, dfops, del->br_startblock,
                                        del->br_blockcount, NULL);
        }

        /*
         * Adjust inode # blocks in the file.
         */
        if (nblks)
                ip->i_d.di_nblocks -= nblks;
        /*
         * Adjust quota data.
         */
        if (qfield && !(bflags & XFS_BMAPI_REMAP))
                xfs_trans_mod_dquot_byino(tp, ip, qfield, (long)-nblks);

done:
        *logflagsp = flags;
        return error;
}

/*
 * Unmap (remove) blocks from a file.
 * If nexts is nonzero then the number of extents to remove is limited to
 * that value.  If not all extents in the block range can be removed then
 * *done is set.
 */
int                                             /* error */
__xfs_bunmapi(
        xfs_trans_t             *tp,            /* transaction pointer */
        struct xfs_inode        *ip,            /* incore inode */
        xfs_fileoff_t           start,          /* first file offset deleted */
        xfs_filblks_t           *rlen,          /* i/o: amount remaining */
        int                     flags,          /* misc flags */
        xfs_extnum_t            nexts,          /* number of extents max */
        xfs_fsblock_t           *firstblock,    /* first allocated block
                                                   controls a.g. for allocs */
        struct xfs_defer_ops    *dfops)         /* i/o: deferred updates */
{
        xfs_btree_cur_t         *cur;           /* bmap btree cursor */
        xfs_bmbt_irec_t         del;            /* extent being deleted */
        int                     error;          /* error return value */
        xfs_extnum_t            extno;          /* extent number in list */
        xfs_bmbt_irec_t         got;            /* current extent record */
        xfs_ifork_t             *ifp;           /* inode fork pointer */
        int                     isrt;           /* freeing in rt area */
        xfs_extnum_t            lastx;          /* last extent index used */
        int                     logflags;       /* transaction logging flags */
        xfs_extlen_t            mod;            /* rt extent offset */
        xfs_mount_t             *mp;            /* mount structure */
        int                     tmp_logflags;   /* partial logging flags */
        int                     wasdel;         /* was a delayed alloc extent */
        int                     whichfork;      /* data or attribute fork */
        xfs_fsblock_t           sum;
        xfs_filblks_t           len = *rlen;    /* length to unmap in file */
        xfs_fileoff_t           max_len;
        xfs_agnumber_t          prev_agno = NULLAGNUMBER, agno;
        xfs_fileoff_t           end;

        trace_xfs_bunmap(ip, start, len, flags, _RET_IP_);

        whichfork = xfs_bmapi_whichfork(flags);
        ASSERT(whichfork != XFS_COW_FORK);
        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (unlikely(
            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE)) {
                XFS_ERROR_REPORT("xfs_bunmapi", XFS_ERRLEVEL_LOW,
                                 ip->i_mount);
                return -EFSCORRUPTED;
        }
        mp = ip->i_mount;
        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(len > 0);
        ASSERT(nexts >= 0);

        /*
         * Guesstimate how many blocks we can unmap without running the risk of
         * blowing out the transaction with a mix of EFIs and reflink
         * adjustments.
         */
        if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK)
                max_len = min(len, xfs_refcount_max_unmap(tp->t_log_res));
        else
                max_len = len;

        if (!(ifp->if_flags & XFS_IFEXTENTS) &&
            (error = xfs_iread_extents(tp, ip, whichfork)))
                return error;
        if (xfs_iext_count(ifp) == 0) {
                *rlen = 0;
                return 0;
        }
        XFS_STATS_INC(mp, xs_blk_unmap);
        isrt = (whichfork == XFS_DATA_FORK) && XFS_IS_REALTIME_INODE(ip);
        end = start + len - 1;

        /*
         * Check to see if the given block number is past the end of the
         * file, back up to the last block if so...
         */
        if (!xfs_iext_lookup_extent(ip, ifp, end, &lastx, &got)) {
                ASSERT(lastx > 0);
                xfs_iext_get_extent(ifp, --lastx, &got);
                end = got.br_startoff + got.br_blockcount - 1;
        }

        logflags = 0;
        if (ifp->if_flags & XFS_IFBROOT) {
                ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE);
                cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
                cur->bc_private.b.firstblock = *firstblock;
                cur->bc_private.b.dfops = dfops;
                cur->bc_private.b.flags = 0;
        } else
                cur = NULL;

        if (isrt) {
                /*
                 * Synchronize by locking the bitmap inode.
                 */
                xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL|XFS_ILOCK_RTBITMAP);
                xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
                xfs_ilock(mp->m_rsumip, XFS_ILOCK_EXCL|XFS_ILOCK_RTSUM);
                xfs_trans_ijoin(tp, mp->m_rsumip, XFS_ILOCK_EXCL);
        }

        extno = 0;
        while (end != (xfs_fileoff_t)-1 && end >= start && lastx >= 0 &&
               (nexts == 0 || extno < nexts) && max_len > 0) {
                /*
                 * Is the found extent after a hole in which end lives?
                 * Just back up to the previous extent, if so.
                 */
                if (got.br_startoff > end) {
                        if (--lastx < 0)
                                break;
                        xfs_iext_get_extent(ifp, lastx, &got);
                }
                /*
                 * Is the last block of this extent before the range
                 * we're supposed to delete?  If so, we're done.
                 */
                end = XFS_FILEOFF_MIN(end,
                        got.br_startoff + got.br_blockcount - 1);
                if (end < start)
                        break;
                /*
                 * Then deal with the (possibly delayed) allocated space
                 * we found.
                 */
                del = got;
                wasdel = isnullstartblock(del.br_startblock);

                /*
                 * Make sure we don't touch multiple AGF headers out of order
                 * in a single transaction, as that could cause AB-BA deadlocks.
                 */
                if (!wasdel) {
                        agno = XFS_FSB_TO_AGNO(mp, del.br_startblock);
                        if (prev_agno != NULLAGNUMBER && prev_agno > agno)
                                break;
                        prev_agno = agno;
                }
                if (got.br_startoff < start) {
                        del.br_startoff = start;
                        del.br_blockcount -= start - got.br_startoff;
                        if (!wasdel)
                                del.br_startblock += start - got.br_startoff;
                }
                if (del.br_startoff + del.br_blockcount > end + 1)
                        del.br_blockcount = end + 1 - del.br_startoff;

                /* How much can we safely unmap? */
                if (max_len < del.br_blockcount) {
                        del.br_startoff += del.br_blockcount - max_len;
                        if (!wasdel)
                                del.br_startblock += del.br_blockcount - max_len;
                        del.br_blockcount = max_len;
                }

                sum = del.br_startblock + del.br_blockcount;
                if (isrt &&
                    (mod = do_mod(sum, mp->m_sb.sb_rextsize))) {
                        /*
                         * Realtime extent not lined up at the end.
                         * The extent could have been split into written
                         * and unwritten pieces, or we could just be
                         * unmapping part of it.  But we can't really
                         * get rid of part of a realtime extent.
                         */
                        if (del.br_state == XFS_EXT_UNWRITTEN ||
                            !xfs_sb_version_hasextflgbit(&mp->m_sb)) {
                                /*
                                 * This piece is unwritten, or we're not
                                 * using unwritten extents.  Skip over it.
                                 */
                                ASSERT(end >= mod);
                                end -= mod > del.br_blockcount ?
                                        del.br_blockcount : mod;
                                if (end < got.br_startoff) {
                                        if (--lastx >= 0)
                                                xfs_iext_get_extent(ifp, lastx,
                                                                &got);
                                }
                                continue;
                        }
                        /*
                         * It's written, turn it unwritten.
                         * This is better than zeroing it.
                         */
                        ASSERT(del.br_state == XFS_EXT_NORM);
                        ASSERT(tp->t_blk_res > 0);
                        /*
                         * If this spans a realtime extent boundary,
                         * chop it back to the start of the one we end at.
                         */
                        if (del.br_blockcount > mod) {
                                del.br_startoff += del.br_blockcount - mod;
                                del.br_startblock += del.br_blockcount - mod;
                                del.br_blockcount = mod;
                        }
                        del.br_state = XFS_EXT_UNWRITTEN;
                        error = xfs_bmap_add_extent_unwritten_real(tp, ip,
                                        whichfork, &lastx, &cur, &del,
                                        firstblock, dfops, &logflags);
                        if (error)
                                goto error0;
                        goto nodelete;
                }
                if (isrt && (mod = do_mod(del.br_startblock, mp->m_sb.sb_rextsize))) {
                        /*
                         * Realtime extent is lined up at the end but not
                         * at the front.  We'll get rid of full extents if
                         * we can.
                         */
                        mod = mp->m_sb.sb_rextsize - mod;
                        if (del.br_blockcount > mod) {
                                del.br_blockcount -= mod;
                                del.br_startoff += mod;
                                del.br_startblock += mod;
                        } else if ((del.br_startoff == start &&
                                    (del.br_state == XFS_EXT_UNWRITTEN ||
                                     tp->t_blk_res == 0)) ||
                                   !xfs_sb_version_hasextflgbit(&mp->m_sb)) {
                                /*
                                 * Can't make it unwritten.  There isn't
                                 * a full extent here so just skip it.
                                 */
                                ASSERT(end >= del.br_blockcount);
                                end -= del.br_blockcount;
                                if (got.br_startoff > end && --lastx >= 0)
                                        xfs_iext_get_extent(ifp, lastx, &got);
                                continue;
                        } else if (del.br_state == XFS_EXT_UNWRITTEN) {
                                struct xfs_bmbt_irec    prev;

                                /*
                                 * This one is already unwritten.
                                 * It must have a written left neighbor.
                                 * Unwrite the killed part of that one and
                                 * try again.
                                 */
                                ASSERT(lastx > 0);
                                xfs_iext_get_extent(ifp, lastx - 1, &prev);
                                ASSERT(prev.br_state == XFS_EXT_NORM);
                                ASSERT(!isnullstartblock(prev.br_startblock));
                                ASSERT(del.br_startblock ==
                                       prev.br_startblock + prev.br_blockcount);
                                if (prev.br_startoff < start) {
                                        mod = start - prev.br_startoff;
                                        prev.br_blockcount -= mod;
                                        prev.br_startblock += mod;
                                        prev.br_startoff = start;
                                }
                                prev.br_state = XFS_EXT_UNWRITTEN;
                                lastx--;
                                error = xfs_bmap_add_extent_unwritten_real(tp,
                                                ip, whichfork, &lastx, &cur,
                                                &prev, firstblock, dfops,
                                                &logflags);
                                if (error)
                                        goto error0;
                                goto nodelete;
                        } else {
                                ASSERT(del.br_state == XFS_EXT_NORM);
                                del.br_state = XFS_EXT_UNWRITTEN;
                                error = xfs_bmap_add_extent_unwritten_real(tp,
                                                ip, whichfork, &lastx, &cur,
                                                &del, firstblock, dfops,
                                                &logflags);
                                if (error)
                                        goto error0;
                                goto nodelete;
                        }
                }

                if (wasdel) {
                        error = xfs_bmap_del_extent_delay(ip, whichfork, &lastx,
                                        &got, &del);
                } else {
                        error = xfs_bmap_del_extent_real(ip, tp, &lastx, dfops,
                                        cur, &del, &tmp_logflags, whichfork,
                                        flags);
                        logflags |= tmp_logflags;
                }

                if (error)
                        goto error0;

                max_len -= del.br_blockcount;
                end = del.br_startoff - 1;
nodelete:
                /*
                 * If not done go on to the next (previous) record.
                 */
                if (end != (xfs_fileoff_t)-1 && end >= start) {
                        if (lastx >= 0) {
                                xfs_iext_get_extent(ifp, lastx, &got);
                                if (got.br_startoff > end && --lastx >= 0)
                                        xfs_iext_get_extent(ifp, lastx, &got);
                        }
                        extno++;
                }
        }
        if (end == (xfs_fileoff_t)-1 || end < start || lastx < 0)
                *rlen = 0;
        else
                *rlen = end - start + 1;

        /*
         * Convert to a btree if necessary.
         */
        if (xfs_bmap_needs_btree(ip, whichfork)) {
                ASSERT(cur == NULL);
                error = xfs_bmap_extents_to_btree(tp, ip, firstblock, dfops,
                        &cur, 0, &tmp_logflags, whichfork);
                logflags |= tmp_logflags;
                if (error)
                        goto error0;
        }
        /*
         * transform from btree to extents, give it cur
         */
        else if (xfs_bmap_wants_extents(ip, whichfork)) {
                ASSERT(cur != NULL);
                error = xfs_bmap_btree_to_extents(tp, ip, cur, &tmp_logflags,
                        whichfork);
                logflags |= tmp_logflags;
                if (error)
                        goto error0;
        }
        /*
         * transform from extents to local?
         */
        error = 0;
error0:
        /*
         * Log everything.  Do this after conversion, there's no point in
         * logging the extent records if we've converted to btree format.
         */
        if ((logflags & xfs_ilog_fext(whichfork)) &&
            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS)
                logflags &= ~xfs_ilog_fext(whichfork);
        else if ((logflags & xfs_ilog_fbroot(whichfork)) &&
                 XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE)
                logflags &= ~xfs_ilog_fbroot(whichfork);
        /*
         * Log inode even in the error case, if the transaction
         * is dirty we'll need to shut down the filesystem.
         */
        if (logflags)
                xfs_trans_log_inode(tp, ip, logflags);
        if (cur) {
                if (!error) {
                        *firstblock = cur->bc_private.b.firstblock;
                        cur->bc_private.b.allocated = 0;
                }
                xfs_btree_del_cursor(cur,
                        error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        }
        return error;
}

/* Unmap a range of a file. */
int
xfs_bunmapi(
        xfs_trans_t             *tp,
        struct xfs_inode        *ip,
        xfs_fileoff_t           bno,
        xfs_filblks_t           len,
        int                     flags,
        xfs_extnum_t            nexts,
        xfs_fsblock_t           *firstblock,
        struct xfs_defer_ops    *dfops,
        int                     *done)
{
        int                     error;

        error = __xfs_bunmapi(tp, ip, bno, &len, flags, nexts, firstblock,
                        dfops);
        *done = (len == 0);
        return error;
}

/*
 * Determine whether an extent shift can be accomplished by a merge with the
 * extent that precedes the target hole of the shift.
 */
STATIC bool
xfs_bmse_can_merge(
        struct xfs_bmbt_irec    *left,  /* preceding extent */
        struct xfs_bmbt_irec    *got,   /* current extent to shift */
        xfs_fileoff_t           shift)  /* shift fsb */
{
        xfs_fileoff_t           startoff;

        startoff = got->br_startoff - shift;

        /*
         * The extent, once shifted, must be adjacent in-file and on-disk with
         * the preceding extent.
         */
        if ((left->br_startoff + left->br_blockcount != startoff) ||
            (left->br_startblock + left->br_blockcount != got->br_startblock) ||
            (left->br_state != got->br_state) ||
            (left->br_blockcount + got->br_blockcount > MAXEXTLEN))
                return false;

        return true;
}

/*
 * A bmap extent shift adjusts the file offset of an extent to fill a preceding
 * hole in the file. If an extent shift would result in the extent being fully
 * adjacent to the extent that currently precedes the hole, we can merge with
 * the preceding extent rather than do the shift.
 *
 * This function assumes the caller has verified a shift-by-merge is possible
 * with the provided extents via xfs_bmse_can_merge().
 */
STATIC int
xfs_bmse_merge(
        struct xfs_inode                *ip,
        int                             whichfork,
        xfs_fileoff_t                   shift,          /* shift fsb */
        int                             current_ext,    /* idx of gotp */
        struct xfs_bmbt_irec            *got,           /* extent to shift */
        struct xfs_bmbt_irec            *left,          /* preceding extent */
        struct xfs_btree_cur            *cur,
        int                             *logflags,      /* output */
        struct xfs_defer_ops            *dfops)
{
        struct xfs_bmbt_irec            new;
        xfs_filblks_t                   blockcount;
        int                             error, i;
        struct xfs_mount                *mp = ip->i_mount;

        blockcount = left->br_blockcount + got->br_blockcount;

        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(xfs_bmse_can_merge(left, got, shift));

        new = *left;
        new.br_blockcount = blockcount;

        /*
         * Update the on-disk extent count, the btree if necessary and log the
         * inode.
         */
        XFS_IFORK_NEXT_SET(ip, whichfork,
                           XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
        *logflags |= XFS_ILOG_CORE;
        if (!cur) {
                *logflags |= XFS_ILOG_DEXT;
                goto done;
        }

        /* lookup and remove the extent to merge */
        error = xfs_bmbt_lookup_eq(cur, got, &i);
        if (error)
                return error;
        XFS_WANT_CORRUPTED_RETURN(mp, i == 1);

        error = xfs_btree_delete(cur, &i);
        if (error)
                return error;
        XFS_WANT_CORRUPTED_RETURN(mp, i == 1);

        /* lookup and update size of the previous extent */
        error = xfs_bmbt_lookup_eq(cur, left, &i);
        if (error)
                return error;
        XFS_WANT_CORRUPTED_RETURN(mp, i == 1);

        error = xfs_bmbt_update(cur, &new);
        if (error)
                return error;

done:
        xfs_iext_update_extent(ip, xfs_bmap_fork_to_state(whichfork),
                        current_ext - 1, &new);
        xfs_iext_remove(ip, current_ext, 1, 0);

        /* update reverse mapping. rmap functions merge the rmaps for us */
        error = xfs_rmap_unmap_extent(mp, dfops, ip, whichfork, got);
        if (error)
                return error;
        memcpy(&new, got, sizeof(new));
        new.br_startoff = left->br_startoff + left->br_blockcount;
        return xfs_rmap_map_extent(mp, dfops, ip, whichfork, &new);
}

/*
 * Shift a single extent.
 */
STATIC int
xfs_bmse_shift_one(
        struct xfs_inode                *ip,
        int                             whichfork,
        xfs_fileoff_t                   offset_shift_fsb,
        int                             *current_ext,
        struct xfs_bmbt_irec            *got,
        struct xfs_btree_cur            *cur,
        int                             *logflags,
        enum shift_direction            direction,
        struct xfs_defer_ops            *dfops)
{
        struct xfs_ifork                *ifp;
        struct xfs_mount                *mp;
        xfs_fileoff_t                   startoff;
        struct xfs_bmbt_irec            adj_irec, new;
        int                             error;
        int                             i;
        int                             total_extents;

        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        total_extents = xfs_iext_count(ifp);

        /* delalloc extents should be prevented by caller */
        XFS_WANT_CORRUPTED_RETURN(mp, !isnullstartblock(got->br_startblock));

        if (direction == SHIFT_LEFT) {
                startoff = got->br_startoff - offset_shift_fsb;

                /*
                 * Check for merge if we've got an extent to the left,
                 * otherwise make sure there's enough room at the start
                 * of the file for the shift.
                 */
                if (!*current_ext) {
                        if (got->br_startoff < offset_shift_fsb)
                                return -EINVAL;
                        goto update_current_ext;
                }

                /*
                 * grab the left extent and check for a large enough hole.
                 */
                xfs_iext_get_extent(ifp, *current_ext - 1, &adj_irec);
                if (startoff < adj_irec.br_startoff + adj_irec.br_blockcount)
                        return -EINVAL;

                /* check whether to merge the extent or shift it down */
                if (xfs_bmse_can_merge(&adj_irec, got, offset_shift_fsb)) {
                        return xfs_bmse_merge(ip, whichfork, offset_shift_fsb,
                                              *current_ext, got, &adj_irec,
                                              cur, logflags, dfops);
                }
        } else {
                startoff = got->br_startoff + offset_shift_fsb;
                /* nothing to move if this is the last extent */
                if (*current_ext >= (total_extents - 1))
                        goto update_current_ext;

                /*
                 * If this is not the last extent in the file, make sure there
                 * is enough room between current extent and next extent for
                 * accommodating the shift.
                 */
                xfs_iext_get_extent(ifp, *current_ext + 1, &adj_irec);
                if (startoff + got->br_blockcount > adj_irec.br_startoff)
                        return -EINVAL;

                /*
                 * Unlike a left shift (which involves a hole punch),
                 * a right shift does not modify extent neighbors
                 * in any way. We should never find mergeable extents
                 * in this scenario. Check anyways and warn if we
                 * encounter two extents that could be one.
                 */
                if (xfs_bmse_can_merge(got, &adj_irec, offset_shift_fsb))
                        WARN_ON_ONCE(1);
        }

        /*
         * Increment the extent index for the next iteration, update the start
         * offset of the in-core extent and update the btree if applicable.
         */
update_current_ext:
        *logflags |= XFS_ILOG_CORE;

        new = *got;
        new.br_startoff = startoff;

        if (cur) {
                error = xfs_bmbt_lookup_eq(cur, got, &i);
                if (error)
                        return error;
                XFS_WANT_CORRUPTED_RETURN(mp, i == 1);

                error = xfs_bmbt_update(cur, &new);
                if (error)
                        return error;
        } else {
                *logflags |= XFS_ILOG_DEXT;
        }

        xfs_iext_update_extent(ip, xfs_bmap_fork_to_state(whichfork),
                        *current_ext, &new);

        if (direction == SHIFT_LEFT)
                (*current_ext)++;
        else
                (*current_ext)--;

        /* update reverse mapping */
        error = xfs_rmap_unmap_extent(mp, dfops, ip, whichfork, got);
        if (error)
                return error;
        return xfs_rmap_map_extent(mp, dfops, ip, whichfork, &new);
}

/*
 * Shift extent records to the left/right to cover/create a hole.
 *
 * The maximum number of extents to be shifted in a single operation is
 * @num_exts. @stop_fsb specifies the file offset at which to stop shift and the
 * file offset where we've left off is returned in @next_fsb. @offset_shift_fsb
 * is the length by which each extent is shifted. If there is no hole to shift
 * the extents into, this will be considered invalid operation and we abort
 * immediately.
 */
int
xfs_bmap_shift_extents(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        xfs_fileoff_t           *next_fsb,
        xfs_fileoff_t           offset_shift_fsb,
        int                     *done,
        xfs_fileoff_t           stop_fsb,
        xfs_fsblock_t           *firstblock,
        struct xfs_defer_ops    *dfops,
        enum shift_direction    direction,
        int                     num_exts)
{
        struct xfs_btree_cur            *cur = NULL;
        struct xfs_bmbt_irec            got;
        struct xfs_mount                *mp = ip->i_mount;
        struct xfs_ifork                *ifp;
        xfs_extnum_t                    nexts = 0;
        xfs_extnum_t                    current_ext;
        xfs_extnum_t                    total_extents;
        xfs_extnum_t                    stop_extent;
        int                             error = 0;
        int                             whichfork = XFS_DATA_FORK;
        int                             logflags = 0;

        if (unlikely(XFS_TEST_ERROR(
            (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
             XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
             mp, XFS_ERRTAG_BMAPIFORMAT))) {
                XFS_ERROR_REPORT("xfs_bmap_shift_extents",
                                 XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(direction == SHIFT_LEFT || direction == SHIFT_RIGHT);

        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                /* Read in all the extents */
                error = xfs_iread_extents(tp, ip, whichfork);
                if (error)
                        return error;
        }

        if (ifp->if_flags & XFS_IFBROOT) {
                cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
                cur->bc_private.b.firstblock = *firstblock;
                cur->bc_private.b.dfops = dfops;
                cur->bc_private.b.flags = 0;
        }

        /*
         * There may be delalloc extents in the data fork before the range we
         * are collapsing out, so we cannot use the count of real extents here.
         * Instead we have to calculate it from the incore fork.
         */
        total_extents = xfs_iext_count(ifp);
        if (total_extents == 0) {
                *done = 1;
                goto del_cursor;
        }

        /*
         * In case of first right shift, we need to initialize next_fsb
         */
        if (*next_fsb == NULLFSBLOCK) {
                ASSERT(direction == SHIFT_RIGHT);

                current_ext = total_extents - 1;
                xfs_iext_get_extent(ifp, current_ext, &got);
                if (stop_fsb > got.br_startoff) {
                        *done = 1;
                        goto del_cursor;
                }
                *next_fsb = got.br_startoff;
        } else {
                /*
                 * Look up the extent index for the fsb where we start shifting. We can
                 * henceforth iterate with current_ext as extent list changes are locked
                 * out via ilock.
                 *
                 * If next_fsb lies in a hole beyond which there are no extents we are
                 * done.
                 */
                if (!xfs_iext_lookup_extent(ip, ifp, *next_fsb, &current_ext,
                                &got)) {
                        *done = 1;
                        goto del_cursor;
                }
        }

        /* Lookup the extent index at which we have to stop */
        if (direction == SHIFT_RIGHT) {
                struct xfs_bmbt_irec s;

                xfs_iext_lookup_extent(ip, ifp, stop_fsb, &stop_extent, &s);
                /* Make stop_extent exclusive of shift range */
                stop_extent--;
                if (current_ext <= stop_extent) {
                        error = -EIO;
                        goto del_cursor;
                }
        } else {
                stop_extent = total_extents;
                if (current_ext >= stop_extent) {
                        error = -EIO;
                        goto del_cursor;
                }
        }

        while (nexts++ < num_exts) {
                error = xfs_bmse_shift_one(ip, whichfork, offset_shift_fsb,
                                           &current_ext, &got, cur, &logflags,
                                           direction, dfops);
                if (error)
                        goto del_cursor;
                /*
                 * If there was an extent merge during the shift, the extent
                 * count can change. Update the total and grade the next record.
                 */
                if (direction == SHIFT_LEFT) {
                        total_extents = xfs_iext_count(ifp);
                        stop_extent = total_extents;
                }

                if (current_ext == stop_extent) {
                        *done = 1;
                        *next_fsb = NULLFSBLOCK;
                        break;
                }
                xfs_iext_get_extent(ifp, current_ext, &got);
        }

        if (!*done)
                *next_fsb = got.br_startoff;

del_cursor:
        if (cur)
                xfs_btree_del_cursor(cur,
                        error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);

        if (logflags)
                xfs_trans_log_inode(tp, ip, logflags);

        return error;
}

/*
 * Splits an extent into two extents at split_fsb block such that it is
 * the first block of the current_ext. @current_ext is a target extent
 * to be split. @split_fsb is a block where the extents is split.
 * If split_fsb lies in a hole or the first block of extents, just return 0.
 */
STATIC int
xfs_bmap_split_extent_at(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        xfs_fileoff_t           split_fsb,
        xfs_fsblock_t           *firstfsb,
        struct xfs_defer_ops    *dfops)
{
        int                             whichfork = XFS_DATA_FORK;
        struct xfs_btree_cur            *cur = NULL;
        struct xfs_bmbt_irec            got;
        struct xfs_bmbt_irec            new; /* split extent */
        struct xfs_mount                *mp = ip->i_mount;
        struct xfs_ifork                *ifp;
        xfs_fsblock_t                   gotblkcnt; /* new block count for got */
        xfs_extnum_t                    current_ext;
        int                             error = 0;
        int                             logflags = 0;
        int                             i = 0;

        if (unlikely(XFS_TEST_ERROR(
            (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
             XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
             mp, XFS_ERRTAG_BMAPIFORMAT))) {
                XFS_ERROR_REPORT("xfs_bmap_split_extent_at",
                                 XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                /* Read in all the extents */
                error = xfs_iread_extents(tp, ip, whichfork);
                if (error)
                        return error;
        }

        /*
         * If there are not extents, or split_fsb lies in a hole we are done.
         */
        if (!xfs_iext_lookup_extent(ip, ifp, split_fsb, &current_ext, &got) ||
            got.br_startoff >= split_fsb)
                return 0;

        gotblkcnt = split_fsb - got.br_startoff;
        new.br_startoff = split_fsb;
        new.br_startblock = got.br_startblock + gotblkcnt;
        new.br_blockcount = got.br_blockcount - gotblkcnt;
        new.br_state = got.br_state;

        if (ifp->if_flags & XFS_IFBROOT) {
                cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
                cur->bc_private.b.firstblock = *firstfsb;
                cur->bc_private.b.dfops = dfops;
                cur->bc_private.b.flags = 0;
                error = xfs_bmbt_lookup_eq(cur, &got, &i);
                if (error)
                        goto del_cursor;
                XFS_WANT_CORRUPTED_GOTO(mp, i == 1, del_cursor);
        }

        got.br_blockcount = gotblkcnt;
        xfs_iext_update_extent(ip, xfs_bmap_fork_to_state(whichfork),
                        current_ext, &got);

        logflags = XFS_ILOG_CORE;
        if (cur) {
                error = xfs_bmbt_update(cur, &got);
                if (error)
                        goto del_cursor;
        } else
                logflags |= XFS_ILOG_DEXT;

        /* Add new extent */
        current_ext++;
        xfs_iext_insert(ip, current_ext, 1, &new, 0);
        XFS_IFORK_NEXT_SET(ip, whichfork,
                           XFS_IFORK_NEXTENTS(ip, whichfork) + 1);

        if (cur) {
                error = xfs_bmbt_lookup_eq(cur, &new, &i);
                if (error)
                        goto del_cursor;
                XFS_WANT_CORRUPTED_GOTO(mp, i == 0, del_cursor);
                error = xfs_btree_insert(cur, &i);
                if (error)
                        goto del_cursor;
                XFS_WANT_CORRUPTED_GOTO(mp, i == 1, del_cursor);
        }

        /*
         * Convert to a btree if necessary.
         */
        if (xfs_bmap_needs_btree(ip, whichfork)) {
                int tmp_logflags; /* partial log flag return val */

                ASSERT(cur == NULL);
                error = xfs_bmap_extents_to_btree(tp, ip, firstfsb, dfops,
                                &cur, 0, &tmp_logflags, whichfork);
                logflags |= tmp_logflags;
        }

del_cursor:
        if (cur) {
                cur->bc_private.b.allocated = 0;
                xfs_btree_del_cursor(cur,
                                error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        }

        if (logflags)
                xfs_trans_log_inode(tp, ip, logflags);
        return error;
}

int
xfs_bmap_split_extent(
        struct xfs_inode        *ip,
        xfs_fileoff_t           split_fsb)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        struct xfs_defer_ops    dfops;
        xfs_fsblock_t           firstfsb;
        int                     error;

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write,
                        XFS_DIOSTRAT_SPACE_RES(mp, 0), 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

        xfs_defer_init(&dfops, &firstfsb);

        error = xfs_bmap_split_extent_at(tp, ip, split_fsb,
                        &firstfsb, &dfops);
        if (error)
                goto out;

        error = xfs_defer_finish(&tp, &dfops);
        if (error)
                goto out;

        return xfs_trans_commit(tp);

out:
        xfs_defer_cancel(&dfops);
        xfs_trans_cancel(tp);
        return error;
}

/* Deferred mapping is only for real extents in the data fork. */
static bool
xfs_bmap_is_update_needed(
        struct xfs_bmbt_irec    *bmap)
{
        return  bmap->br_startblock != HOLESTARTBLOCK &&
                bmap->br_startblock != DELAYSTARTBLOCK;
}

/* Record a bmap intent. */
static int
__xfs_bmap_add(
        struct xfs_mount                *mp,
        struct xfs_defer_ops            *dfops,
        enum xfs_bmap_intent_type       type,
        struct xfs_inode                *ip,
        int                             whichfork,
        struct xfs_bmbt_irec            *bmap)
{
        int                             error;
        struct xfs_bmap_intent          *bi;

        trace_xfs_bmap_defer(mp,
                        XFS_FSB_TO_AGNO(mp, bmap->br_startblock),
                        type,
                        XFS_FSB_TO_AGBNO(mp, bmap->br_startblock),
                        ip->i_ino, whichfork,
                        bmap->br_startoff,
                        bmap->br_blockcount,
                        bmap->br_state);

        bi = kmem_alloc(sizeof(struct xfs_bmap_intent), KM_SLEEP | KM_NOFS);
        INIT_LIST_HEAD(&bi->bi_list);
        bi->bi_type = type;
        bi->bi_owner = ip;
        bi->bi_whichfork = whichfork;
        bi->bi_bmap = *bmap;

        error = xfs_defer_ijoin(dfops, bi->bi_owner);
        if (error) {
                kmem_free(bi);
                return error;
        }

        xfs_defer_add(dfops, XFS_DEFER_OPS_TYPE_BMAP, &bi->bi_list);
        return 0;
}

/* Map an extent into a file. */
int
xfs_bmap_map_extent(
        struct xfs_mount        *mp,
        struct xfs_defer_ops    *dfops,
        struct xfs_inode        *ip,
        struct xfs_bmbt_irec    *PREV)
{
        if (!xfs_bmap_is_update_needed(PREV))
                return 0;

        return __xfs_bmap_add(mp, dfops, XFS_BMAP_MAP, ip,
                        XFS_DATA_FORK, PREV);
}

/* Unmap an extent out of a file. */
int
xfs_bmap_unmap_extent(
        struct xfs_mount        *mp,
        struct xfs_defer_ops    *dfops,
        struct xfs_inode        *ip,
        struct xfs_bmbt_irec    *PREV)
{
        if (!xfs_bmap_is_update_needed(PREV))
                return 0;

        return __xfs_bmap_add(mp, dfops, XFS_BMAP_UNMAP, ip,
                        XFS_DATA_FORK, PREV);
}

/*
 * Process one of the deferred bmap operations.  We pass back the
 * btree cursor to maintain our lock on the bmapbt between calls.
 */
int
xfs_bmap_finish_one(
        struct xfs_trans                *tp,
        struct xfs_defer_ops            *dfops,
        struct xfs_inode                *ip,
        enum xfs_bmap_intent_type       type,
        int                             whichfork,
        xfs_fileoff_t                   startoff,
        xfs_fsblock_t                   startblock,
        xfs_filblks_t                   *blockcount,
        xfs_exntst_t                    state)
{
        xfs_fsblock_t                   firstfsb;
        int                             error = 0;

        /*
         * firstfsb is tied to the transaction lifetime and is used to
         * ensure correct AG locking order and schedule work item
         * continuations.  XFS_BUI_MAX_FAST_EXTENTS (== 1) restricts us
         * to only making one bmap call per transaction, so it should
         * be safe to have it as a local variable here.
         */
        firstfsb = NULLFSBLOCK;

        trace_xfs_bmap_deferred(tp->t_mountp,
                        XFS_FSB_TO_AGNO(tp->t_mountp, startblock), type,
                        XFS_FSB_TO_AGBNO(tp->t_mountp, startblock),
                        ip->i_ino, whichfork, startoff, *blockcount, state);

        if (WARN_ON_ONCE(whichfork != XFS_DATA_FORK))
                return -EFSCORRUPTED;

        if (XFS_TEST_ERROR(false, tp->t_mountp,
                        XFS_ERRTAG_BMAP_FINISH_ONE))
                return -EIO;

        switch (type) {
        case XFS_BMAP_MAP:
                error = xfs_bmapi_remap(tp, ip, startoff, *blockcount,
                                startblock, dfops);
                *blockcount = 0;
                break;
        case XFS_BMAP_UNMAP:
                error = __xfs_bunmapi(tp, ip, startoff, blockcount,
                                XFS_BMAPI_REMAP, 1, &firstfsb, dfops);
                break;
        default:
                ASSERT(0);
                error = -EFSCORRUPTED;
        }

        return error;
}