xfs: verify inline directory data forks

[thirdparty/xfsprogs-dev.git] / libxfs / xfs_inode_fork.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_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_bmap.h"
#include "xfs_trace.h"
#include "xfs_attr_sf.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_dir2_priv.h"


kmem_zone_t *xfs_ifork_zone;

STATIC int xfs_iformat_local(xfs_inode_t *, xfs_dinode_t *, int, int);
STATIC int xfs_iformat_extents(xfs_inode_t *, xfs_dinode_t *, int);
STATIC int xfs_iformat_btree(xfs_inode_t *, xfs_dinode_t *, int);

#ifdef DEBUG
/*
 * Make sure that the extents in the given memory buffer
 * are valid.
 */
void
xfs_validate_extents(
        xfs_ifork_t             *ifp,
        int                     nrecs,
        xfs_exntfmt_t           fmt)
{
        xfs_bmbt_irec_t         irec;
        xfs_bmbt_rec_host_t     rec;
        int                     i;

        for (i = 0; i < nrecs; i++) {
                xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
                rec.l0 = get_unaligned(&ep->l0);
                rec.l1 = get_unaligned(&ep->l1);
                xfs_bmbt_get_all(&rec, &irec);
                if (fmt == XFS_EXTFMT_NOSTATE)
                        ASSERT(irec.br_state == XFS_EXT_NORM);
        }
}
#else /* DEBUG */
#define xfs_validate_extents(ifp, nrecs, fmt)
#endif /* DEBUG */


/*
 * Move inode type and inode format specific information from the
 * on-disk inode to the in-core inode.  For fifos, devs, and sockets
 * this means set if_rdev to the proper value.  For files, directories,
 * and symlinks this means to bring in the in-line data or extent
 * pointers.  For a file in B-tree format, only the root is immediately
 * brought in-core.  The rest will be in-lined in if_extents when it
 * is first referenced (see xfs_iread_extents()).
 */
int
xfs_iformat_fork(
        xfs_inode_t             *ip,
        xfs_dinode_t            *dip)
{
        xfs_attr_shortform_t    *atp;
        int                     size;
        int                     error = 0;
        xfs_fsize_t             di_size;

        if (unlikely(be32_to_cpu(dip->di_nextents) +
                     be16_to_cpu(dip->di_anextents) >
                     be64_to_cpu(dip->di_nblocks))) {
                xfs_warn(ip->i_mount,
                        "corrupt dinode %Lu, extent total = %d, nblocks = %Lu.",
                        (unsigned long long)ip->i_ino,
                        (int)(be32_to_cpu(dip->di_nextents) +
                              be16_to_cpu(dip->di_anextents)),
                        (unsigned long long)
                                be64_to_cpu(dip->di_nblocks));
                XFS_CORRUPTION_ERROR("xfs_iformat(1)", XFS_ERRLEVEL_LOW,
                                     ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        if (unlikely(dip->di_forkoff > ip->i_mount->m_sb.sb_inodesize)) {
                xfs_warn(ip->i_mount, "corrupt dinode %Lu, forkoff = 0x%x.",
                        (unsigned long long)ip->i_ino,
                        dip->di_forkoff);
                XFS_CORRUPTION_ERROR("xfs_iformat(2)", XFS_ERRLEVEL_LOW,
                                     ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        if (unlikely((ip->i_d.di_flags & XFS_DIFLAG_REALTIME) &&
                     !ip->i_mount->m_rtdev_targp)) {
                xfs_warn(ip->i_mount,
                        "corrupt dinode %Lu, has realtime flag set.",
                        ip->i_ino);
                XFS_CORRUPTION_ERROR("xfs_iformat(realtime)",
                                     XFS_ERRLEVEL_LOW, ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        if (unlikely(xfs_is_reflink_inode(ip) &&
            (VFS_I(ip)->i_mode & S_IFMT) != S_IFREG)) {
                xfs_warn(ip->i_mount,
                        "corrupt dinode %llu, wrong file type for reflink.",
                        ip->i_ino);
                XFS_CORRUPTION_ERROR("xfs_iformat(reflink)",
                                     XFS_ERRLEVEL_LOW, ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        if (unlikely(xfs_is_reflink_inode(ip) &&
            (ip->i_d.di_flags & XFS_DIFLAG_REALTIME))) {
                xfs_warn(ip->i_mount,
                        "corrupt dinode %llu, has reflink+realtime flag set.",
                        ip->i_ino);
                XFS_CORRUPTION_ERROR("xfs_iformat(reflink)",
                                     XFS_ERRLEVEL_LOW, ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        switch (VFS_I(ip)->i_mode & S_IFMT) {
        case S_IFIFO:
        case S_IFCHR:
        case S_IFBLK:
        case S_IFSOCK:
                if (unlikely(dip->di_format != XFS_DINODE_FMT_DEV)) {
                        XFS_CORRUPTION_ERROR("xfs_iformat(3)", XFS_ERRLEVEL_LOW,
                                              ip->i_mount, dip);
                        return -EFSCORRUPTED;
                }
                ip->i_d.di_size = 0;
                ip->i_df.if_u2.if_rdev = xfs_dinode_get_rdev(dip);
                break;

        case S_IFREG:
        case S_IFLNK:
        case S_IFDIR:
                switch (dip->di_format) {
                case XFS_DINODE_FMT_LOCAL:
                        /*
                         * no local regular files yet
                         */
                        if (unlikely(S_ISREG(be16_to_cpu(dip->di_mode)))) {
                                xfs_warn(ip->i_mount,
                        "corrupt inode %Lu (local format for regular file).",
                                        (unsigned long long) ip->i_ino);
                                XFS_CORRUPTION_ERROR("xfs_iformat(4)",
                                                     XFS_ERRLEVEL_LOW,
                                                     ip->i_mount, dip);
                                return -EFSCORRUPTED;
                        }

                        di_size = be64_to_cpu(dip->di_size);
                        if (unlikely(di_size < 0 ||
                                     di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
                                xfs_warn(ip->i_mount,
                        "corrupt inode %Lu (bad size %Ld for local inode).",
                                        (unsigned long long) ip->i_ino,
                                        (long long) di_size);
                                XFS_CORRUPTION_ERROR("xfs_iformat(5)",
                                                     XFS_ERRLEVEL_LOW,
                                                     ip->i_mount, dip);
                                return -EFSCORRUPTED;
                        }

                        size = (int)di_size;
                        error = xfs_iformat_local(ip, dip, XFS_DATA_FORK, size);
                        break;
                case XFS_DINODE_FMT_EXTENTS:
                        error = xfs_iformat_extents(ip, dip, XFS_DATA_FORK);
                        break;
                case XFS_DINODE_FMT_BTREE:
                        error = xfs_iformat_btree(ip, dip, XFS_DATA_FORK);
                        break;
                default:
                        XFS_ERROR_REPORT("xfs_iformat(6)", XFS_ERRLEVEL_LOW,
                                         ip->i_mount);
                        return -EFSCORRUPTED;
                }
                break;

        default:
                XFS_ERROR_REPORT("xfs_iformat(7)", XFS_ERRLEVEL_LOW, ip->i_mount);
                return -EFSCORRUPTED;
        }
        if (error)
                return error;

        if (xfs_is_reflink_inode(ip)) {
                ASSERT(ip->i_cowfp == NULL);
                xfs_ifork_init_cow(ip);
        }

        if (!XFS_DFORK_Q(dip))
                return 0;

        ASSERT(ip->i_afp == NULL);
        ip->i_afp = kmem_zone_zalloc(xfs_ifork_zone, KM_SLEEP | KM_NOFS);

        switch (dip->di_aformat) {
        case XFS_DINODE_FMT_LOCAL:
                atp = (xfs_attr_shortform_t *)XFS_DFORK_APTR(dip);
                size = be16_to_cpu(atp->hdr.totsize);

                if (unlikely(size < sizeof(struct xfs_attr_sf_hdr))) {
                        xfs_warn(ip->i_mount,
                                "corrupt inode %Lu (bad attr fork size %Ld).",
                                (unsigned long long) ip->i_ino,
                                (long long) size);
                        XFS_CORRUPTION_ERROR("xfs_iformat(8)",
                                             XFS_ERRLEVEL_LOW,
                                             ip->i_mount, dip);
                        error = -EFSCORRUPTED;
                        break;
                }

                error = xfs_iformat_local(ip, dip, XFS_ATTR_FORK, size);
                break;
        case XFS_DINODE_FMT_EXTENTS:
                error = xfs_iformat_extents(ip, dip, XFS_ATTR_FORK);
                break;
        case XFS_DINODE_FMT_BTREE:
                error = xfs_iformat_btree(ip, dip, XFS_ATTR_FORK);
                break;
        default:
                error = -EFSCORRUPTED;
                break;
        }
        if (error) {
                kmem_zone_free(xfs_ifork_zone, ip->i_afp);
                ip->i_afp = NULL;
                if (ip->i_cowfp)
                        kmem_zone_free(xfs_ifork_zone, ip->i_cowfp);
                ip->i_cowfp = NULL;
                xfs_idestroy_fork(ip, XFS_DATA_FORK);
        }
        return error;
}

void
xfs_init_local_fork(
        struct xfs_inode        *ip,
        int                     whichfork,
        const void              *data,
        int                     size)
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        int                     mem_size = size, real_size = 0;
        bool                    zero_terminate;

        /*
         * If we are using the local fork to store a symlink body we need to
         * zero-terminate it so that we can pass it back to the VFS directly.
         * Overallocate the in-memory fork by one for that and add a zero
         * to terminate it below.
         */
        zero_terminate = S_ISLNK(VFS_I(ip)->i_mode);
        if (zero_terminate)
                mem_size++;

        if (size == 0)
                ifp->if_u1.if_data = NULL;
        else if (mem_size <= sizeof(ifp->if_u2.if_inline_data))
                ifp->if_u1.if_data = ifp->if_u2.if_inline_data;
        else {
                real_size = roundup(mem_size, 4);
                ifp->if_u1.if_data = kmem_alloc(real_size, KM_SLEEP | KM_NOFS);
        }

        if (size) {
                memcpy(ifp->if_u1.if_data, data, size);
                if (zero_terminate)
                        ifp->if_u1.if_data[size] = '\0';
        }

        ifp->if_bytes = size;
        ifp->if_real_bytes = real_size;
        ifp->if_flags &= ~(XFS_IFEXTENTS | XFS_IFBROOT);
        ifp->if_flags |= XFS_IFINLINE;
}

/*
 * The file is in-lined in the on-disk inode.
 * If it fits into if_inline_data, then copy
 * it there, otherwise allocate a buffer for it
 * and copy the data there.  Either way, set
 * if_data to point at the data.
 * If we allocate a buffer for the data, make
 * sure that its size is a multiple of 4 and
 * record the real size in i_real_bytes.
 */
STATIC int
xfs_iformat_local(
        xfs_inode_t     *ip,
        xfs_dinode_t    *dip,
        int             whichfork,
        int             size)
{
        int             error;

        /*
         * If the size is unreasonable, then something
         * is wrong and we just bail out rather than crash in
         * kmem_alloc() or memcpy() below.
         */
        if (unlikely(size > XFS_DFORK_SIZE(dip, ip->i_mount, whichfork))) {
                xfs_warn(ip->i_mount,
        "corrupt inode %Lu (bad size %d for local fork, size = %d).",
                        (unsigned long long) ip->i_ino, size,
                        XFS_DFORK_SIZE(dip, ip->i_mount, whichfork));
                XFS_CORRUPTION_ERROR("xfs_iformat_local", XFS_ERRLEVEL_LOW,
                                     ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        if (S_ISDIR(VFS_I(ip)->i_mode) && whichfork == XFS_DATA_FORK) {
                error = xfs_dir2_sf_verify(ip->i_mount,
                                (struct xfs_dir2_sf_hdr *)XFS_DFORK_DPTR(dip),
                                size);
                if (error)
                        return error;
        }

        xfs_init_local_fork(ip, whichfork, XFS_DFORK_PTR(dip, whichfork), size);
        return 0;
}

/*
 * The file consists of a set of extents all
 * of which fit into the on-disk inode.
 * If there are few enough extents to fit into
 * the if_inline_ext, then copy them there.
 * Otherwise allocate a buffer for them and copy
 * them into it.  Either way, set if_extents
 * to point at the extents.
 */
STATIC int
xfs_iformat_extents(
        xfs_inode_t     *ip,
        xfs_dinode_t    *dip,
        int             whichfork)
{
        xfs_bmbt_rec_t  *dp;
        xfs_ifork_t     *ifp;
        int             nex;
        int             size;
        int             i;

        ifp = XFS_IFORK_PTR(ip, whichfork);
        nex = XFS_DFORK_NEXTENTS(dip, whichfork);
        size = nex * (uint)sizeof(xfs_bmbt_rec_t);

        /*
         * If the number of extents is unreasonable, then something
         * is wrong and we just bail out rather than crash in
         * kmem_alloc() or memcpy() below.
         */
        if (unlikely(size < 0 || size > XFS_DFORK_SIZE(dip, ip->i_mount, whichfork))) {
                xfs_warn(ip->i_mount, "corrupt inode %Lu ((a)extents = %d).",
                        (unsigned long long) ip->i_ino, nex);
                XFS_CORRUPTION_ERROR("xfs_iformat_extents(1)", XFS_ERRLEVEL_LOW,
                                     ip->i_mount, dip);
                return -EFSCORRUPTED;
        }

        ifp->if_real_bytes = 0;
        if (nex == 0)
                ifp->if_u1.if_extents = NULL;
        else if (nex <= XFS_INLINE_EXTS)
                ifp->if_u1.if_extents = ifp->if_u2.if_inline_ext;
        else
                xfs_iext_add(ifp, 0, nex);

        ifp->if_bytes = size;
        if (size) {
                dp = (xfs_bmbt_rec_t *) XFS_DFORK_PTR(dip, whichfork);
                xfs_validate_extents(ifp, nex, XFS_EXTFMT_INODE(ip));
                for (i = 0; i < nex; i++, dp++) {
                        xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
                        ep->l0 = get_unaligned_be64(&dp->l0);
                        ep->l1 = get_unaligned_be64(&dp->l1);
                }
                XFS_BMAP_TRACE_EXLIST(ip, nex, whichfork);
                if (whichfork != XFS_DATA_FORK ||
                        XFS_EXTFMT_INODE(ip) == XFS_EXTFMT_NOSTATE)
                                if (unlikely(xfs_check_nostate_extents(
                                    ifp, 0, nex))) {
                                        XFS_ERROR_REPORT("xfs_iformat_extents(2)",
                                                         XFS_ERRLEVEL_LOW,
                                                         ip->i_mount);
                                        return -EFSCORRUPTED;
                                }
        }
        ifp->if_flags |= XFS_IFEXTENTS;
        return 0;
}

/*
 * The file has too many extents to fit into
 * the inode, so they are in B-tree format.
 * Allocate a buffer for the root of the B-tree
 * and copy the root into it.  The i_extents
 * field will remain NULL until all of the
 * extents are read in (when they are needed).
 */
STATIC int
xfs_iformat_btree(
        xfs_inode_t             *ip,
        xfs_dinode_t            *dip,
        int                     whichfork)
{
        struct xfs_mount        *mp = ip->i_mount;
        xfs_bmdr_block_t        *dfp;
        xfs_ifork_t             *ifp;
        /* REFERENCED */
        int                     nrecs;
        int                     size;
        int                     level;

        ifp = XFS_IFORK_PTR(ip, whichfork);
        dfp = (xfs_bmdr_block_t *)XFS_DFORK_PTR(dip, whichfork);
        size = XFS_BMAP_BROOT_SPACE(mp, dfp);
        nrecs = be16_to_cpu(dfp->bb_numrecs);
        level = be16_to_cpu(dfp->bb_level);

        /*
         * blow out if -- fork has less extents than can fit in
         * fork (fork shouldn't be a btree format), root btree
         * block has more records than can fit into the fork,
         * or the number of extents is greater than the number of
         * blocks.
         */
        if (unlikely(XFS_IFORK_NEXTENTS(ip, whichfork) <=
                                        XFS_IFORK_MAXEXT(ip, whichfork) ||
                     XFS_BMDR_SPACE_CALC(nrecs) >
                                        XFS_DFORK_SIZE(dip, mp, whichfork) ||
                     XFS_IFORK_NEXTENTS(ip, whichfork) > ip->i_d.di_nblocks) ||
                     level == 0 || level > XFS_BTREE_MAXLEVELS) {
                xfs_warn(mp, "corrupt inode %Lu (btree).",
                                        (unsigned long long) ip->i_ino);
                XFS_CORRUPTION_ERROR("xfs_iformat_btree", XFS_ERRLEVEL_LOW,
                                         mp, dip);
                return -EFSCORRUPTED;
        }

        ifp->if_broot_bytes = size;
        ifp->if_broot = kmem_alloc(size, KM_SLEEP | KM_NOFS);
        ASSERT(ifp->if_broot != NULL);
        /*
         * Copy and convert from the on-disk structure
         * to the in-memory structure.
         */
        xfs_bmdr_to_bmbt(ip, dfp, XFS_DFORK_SIZE(dip, ip->i_mount, whichfork),
                         ifp->if_broot, size);
        ifp->if_flags &= ~XFS_IFEXTENTS;
        ifp->if_flags |= XFS_IFBROOT;

        return 0;
}

/*
 * Read in extents from a btree-format inode.
 * Allocate and fill in if_extents.  Real work is done in xfs_bmap.c.
 */
int
xfs_iread_extents(
        xfs_trans_t     *tp,
        xfs_inode_t     *ip,
        int             whichfork)
{
        int             error;
        xfs_ifork_t     *ifp;
        xfs_extnum_t    nextents;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        if (unlikely(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE)) {
                XFS_ERROR_REPORT("xfs_iread_extents", XFS_ERRLEVEL_LOW,
                                 ip->i_mount);
                return -EFSCORRUPTED;
        }
        nextents = XFS_IFORK_NEXTENTS(ip, whichfork);
        ifp = XFS_IFORK_PTR(ip, whichfork);

        /*
         * We know that the size is valid (it's checked in iformat_btree)
         */
        ifp->if_bytes = ifp->if_real_bytes = 0;
        xfs_iext_add(ifp, 0, nextents);
        error = xfs_bmap_read_extents(tp, ip, whichfork);
        if (error) {
                xfs_iext_destroy(ifp);
                return error;
        }
        xfs_validate_extents(ifp, nextents, XFS_EXTFMT_INODE(ip));
        ifp->if_flags |= XFS_IFEXTENTS;
        return 0;
}
/*
 * Reallocate the space for if_broot based on the number of records
 * being added or deleted as indicated in rec_diff.  Move the records
 * and pointers in if_broot to fit the new size.  When shrinking this
 * will eliminate holes between the records and pointers created by
 * the caller.  When growing this will create holes to be filled in
 * by the caller.
 *
 * The caller must not request to add more records than would fit in
 * the on-disk inode root.  If the if_broot is currently NULL, then
 * if we are adding records, one will be allocated.  The caller must also
 * not request that the number of records go below zero, although
 * it can go to zero.
 *
 * ip -- the inode whose if_broot area is changing
 * ext_diff -- the change in the number of records, positive or negative,
 *       requested for the if_broot array.
 */
void
xfs_iroot_realloc(
        xfs_inode_t             *ip,
        int                     rec_diff,
        int                     whichfork)
{
        struct xfs_mount        *mp = ip->i_mount;
        int                     cur_max;
        xfs_ifork_t             *ifp;
        struct xfs_btree_block  *new_broot;
        int                     new_max;
        size_t                  new_size;
        char                    *np;
        char                    *op;

        /*
         * Handle the degenerate case quietly.
         */
        if (rec_diff == 0) {
                return;
        }

        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (rec_diff > 0) {
                /*
                 * If there wasn't any memory allocated before, just
                 * allocate it now and get out.
                 */
                if (ifp->if_broot_bytes == 0) {
                        new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, rec_diff);
                        ifp->if_broot = kmem_alloc(new_size, KM_SLEEP | KM_NOFS);
                        ifp->if_broot_bytes = (int)new_size;
                        return;
                }

                /*
                 * If there is already an existing if_broot, then we need
                 * to realloc() it and shift the pointers to their new
                 * location.  The records don't change location because
                 * they are kept butted up against the btree block header.
                 */
                cur_max = xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0);
                new_max = cur_max + rec_diff;
                new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, new_max);
                ifp->if_broot = kmem_realloc(ifp->if_broot, new_size,
                                KM_SLEEP | KM_NOFS);
                op = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
                                                     ifp->if_broot_bytes);
                np = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
                                                     (int)new_size);
                ifp->if_broot_bytes = (int)new_size;
                ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
                        XFS_IFORK_SIZE(ip, whichfork));
                memmove(np, op, cur_max * (uint)sizeof(xfs_fsblock_t));
                return;
        }

        /*
         * rec_diff is less than 0.  In this case, we are shrinking the
         * if_broot buffer.  It must already exist.  If we go to zero
         * records, just get rid of the root and clear the status bit.
         */
        ASSERT((ifp->if_broot != NULL) && (ifp->if_broot_bytes > 0));
        cur_max = xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0);
        new_max = cur_max + rec_diff;
        ASSERT(new_max >= 0);
        if (new_max > 0)
                new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, new_max);
        else
                new_size = 0;
        if (new_size > 0) {
                new_broot = kmem_alloc(new_size, KM_SLEEP | KM_NOFS);
                /*
                 * First copy over the btree block header.
                 */
                memcpy(new_broot, ifp->if_broot,
                        XFS_BMBT_BLOCK_LEN(ip->i_mount));
        } else {
                new_broot = NULL;
                ifp->if_flags &= ~XFS_IFBROOT;
        }

        /*
         * Only copy the records and pointers if there are any.
         */
        if (new_max > 0) {
                /*
                 * First copy the records.
                 */
                op = (char *)XFS_BMBT_REC_ADDR(mp, ifp->if_broot, 1);
                np = (char *)XFS_BMBT_REC_ADDR(mp, new_broot, 1);
                memcpy(np, op, new_max * (uint)sizeof(xfs_bmbt_rec_t));

                /*
                 * Then copy the pointers.
                 */
                op = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
                                                     ifp->if_broot_bytes);
                np = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, new_broot, 1,
                                                     (int)new_size);
                memcpy(np, op, new_max * (uint)sizeof(xfs_fsblock_t));
        }
        kmem_free(ifp->if_broot);
        ifp->if_broot = new_broot;
        ifp->if_broot_bytes = (int)new_size;
        if (ifp->if_broot)
                ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
                        XFS_IFORK_SIZE(ip, whichfork));
        return;
}


/*
 * This is called when the amount of space needed for if_data
 * is increased or decreased.  The change in size is indicated by
 * the number of bytes that need to be added or deleted in the
 * byte_diff parameter.
 *
 * If the amount of space needed has decreased below the size of the
 * inline buffer, then switch to using the inline buffer.  Otherwise,
 * use kmem_realloc() or kmem_alloc() to adjust the size of the buffer
 * to what is needed.
 *
 * ip -- the inode whose if_data area is changing
 * byte_diff -- the change in the number of bytes, positive or negative,
 *       requested for the if_data array.
 */
void
xfs_idata_realloc(
        xfs_inode_t     *ip,
        int             byte_diff,
        int             whichfork)
{
        xfs_ifork_t     *ifp;
        int             new_size;
        int             real_size;

        if (byte_diff == 0) {
                return;
        }

        ifp = XFS_IFORK_PTR(ip, whichfork);
        new_size = (int)ifp->if_bytes + byte_diff;
        ASSERT(new_size >= 0);

        if (new_size == 0) {
                if (ifp->if_u1.if_data != ifp->if_u2.if_inline_data) {
                        kmem_free(ifp->if_u1.if_data);
                }
                ifp->if_u1.if_data = NULL;
                real_size = 0;
        } else if (new_size <= sizeof(ifp->if_u2.if_inline_data)) {
                /*
                 * If the valid extents/data can fit in if_inline_ext/data,
                 * copy them from the malloc'd vector and free it.
                 */
                if (ifp->if_u1.if_data == NULL) {
                        ifp->if_u1.if_data = ifp->if_u2.if_inline_data;
                } else if (ifp->if_u1.if_data != ifp->if_u2.if_inline_data) {
                        ASSERT(ifp->if_real_bytes != 0);
                        memcpy(ifp->if_u2.if_inline_data, ifp->if_u1.if_data,
                              new_size);
                        kmem_free(ifp->if_u1.if_data);
                        ifp->if_u1.if_data = ifp->if_u2.if_inline_data;
                }
                real_size = 0;
        } else {
                /*
                 * Stuck with malloc/realloc.
                 * For inline data, the underlying buffer must be
                 * a multiple of 4 bytes in size so that it can be
                 * logged and stay on word boundaries.  We enforce
                 * that here.
                 */
                real_size = roundup(new_size, 4);
                if (ifp->if_u1.if_data == NULL) {
                        ASSERT(ifp->if_real_bytes == 0);
                        ifp->if_u1.if_data = kmem_alloc(real_size,
                                                        KM_SLEEP | KM_NOFS);
                } else if (ifp->if_u1.if_data != ifp->if_u2.if_inline_data) {
                        /*
                         * Only do the realloc if the underlying size
                         * is really changing.
                         */
                        if (ifp->if_real_bytes != real_size) {
                                ifp->if_u1.if_data =
                                        kmem_realloc(ifp->if_u1.if_data,
                                                        real_size,
                                                        KM_SLEEP | KM_NOFS);
                        }
                } else {
                        ASSERT(ifp->if_real_bytes == 0);
                        ifp->if_u1.if_data = kmem_alloc(real_size,
                                                        KM_SLEEP | KM_NOFS);
                        memcpy(ifp->if_u1.if_data, ifp->if_u2.if_inline_data,
                                ifp->if_bytes);
                }
        }
        ifp->if_real_bytes = real_size;
        ifp->if_bytes = new_size;
        ASSERT(ifp->if_bytes <= XFS_IFORK_SIZE(ip, whichfork));
}

void
xfs_idestroy_fork(
        xfs_inode_t     *ip,
        int             whichfork)
{
        xfs_ifork_t     *ifp;

        ifp = XFS_IFORK_PTR(ip, whichfork);
        if (ifp->if_broot != NULL) {
                kmem_free(ifp->if_broot);
                ifp->if_broot = NULL;
        }

        /*
         * If the format is local, then we can't have an extents
         * array so just look for an inline data array.  If we're
         * not local then we may or may not have an extents list,
         * so check and free it up if we do.
         */
        if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL) {
                if ((ifp->if_u1.if_data != ifp->if_u2.if_inline_data) &&
                    (ifp->if_u1.if_data != NULL)) {
                        ASSERT(ifp->if_real_bytes != 0);
                        kmem_free(ifp->if_u1.if_data);
                        ifp->if_u1.if_data = NULL;
                        ifp->if_real_bytes = 0;
                }
        } else if ((ifp->if_flags & XFS_IFEXTENTS) &&
                   ((ifp->if_flags & XFS_IFEXTIREC) ||
                    ((ifp->if_u1.if_extents != NULL) &&
                     (ifp->if_u1.if_extents != ifp->if_u2.if_inline_ext)))) {
                ASSERT(ifp->if_real_bytes != 0);
                xfs_iext_destroy(ifp);
        }
        ASSERT(ifp->if_u1.if_extents == NULL ||
               ifp->if_u1.if_extents == ifp->if_u2.if_inline_ext);
        ASSERT(ifp->if_real_bytes == 0);
        if (whichfork == XFS_ATTR_FORK) {
                kmem_zone_free(xfs_ifork_zone, ip->i_afp);
                ip->i_afp = NULL;
        } else if (whichfork == XFS_COW_FORK) {
                kmem_zone_free(xfs_ifork_zone, ip->i_cowfp);
                ip->i_cowfp = NULL;
        }
}

/* Count number of incore extents based on if_bytes */
xfs_extnum_t
xfs_iext_count(struct xfs_ifork *ifp)
{
        return ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
}

/*
 * Convert in-core extents to on-disk form
 *
 * For either the data or attr fork in extent format, we need to endian convert
 * the in-core extent as we place them into the on-disk inode.
 *
 * In the case of the data fork, the in-core and on-disk fork sizes can be
 * different due to delayed allocation extents. We only copy on-disk extents
 * here, so callers must always use the physical fork size to determine the
 * size of the buffer passed to this routine.  We will return the size actually
 * used.
 */
int
xfs_iextents_copy(
        xfs_inode_t             *ip,
        xfs_bmbt_rec_t          *dp,
        int                     whichfork)
{
        int                     copied;
        int                     i;
        xfs_ifork_t             *ifp;
        int                     nrecs;
        xfs_fsblock_t           start_block;

        ifp = XFS_IFORK_PTR(ip, whichfork);
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
        ASSERT(ifp->if_bytes > 0);

        nrecs = xfs_iext_count(ifp);
        XFS_BMAP_TRACE_EXLIST(ip, nrecs, whichfork);
        ASSERT(nrecs > 0);

        /*
         * There are some delayed allocation extents in the
         * inode, so copy the extents one at a time and skip
         * the delayed ones.  There must be at least one
         * non-delayed extent.
         */
        copied = 0;
        for (i = 0; i < nrecs; i++) {
                xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
                start_block = xfs_bmbt_get_startblock(ep);
                if (isnullstartblock(start_block)) {
                        /*
                         * It's a delayed allocation extent, so skip it.
                         */
                        continue;
                }

                /* Translate to on disk format */
                put_unaligned_be64(ep->l0, &dp->l0);
                put_unaligned_be64(ep->l1, &dp->l1);
                dp++;
                copied++;
        }
        ASSERT(copied != 0);
        xfs_validate_extents(ifp, copied, XFS_EXTFMT_INODE(ip));

        return (copied * (uint)sizeof(xfs_bmbt_rec_t));
}

/*
 * Each of the following cases stores data into the same region
 * of the on-disk inode, so only one of them can be valid at
 * any given time. While it is possible to have conflicting formats
 * and log flags, e.g. having XFS_ILOG_?DATA set when the fork is
 * in EXTENTS format, this can only happen when the fork has
 * changed formats after being modified but before being flushed.
 * In these cases, the format always takes precedence, because the
 * format indicates the current state of the fork.
 */
int
xfs_iflush_fork(
        xfs_inode_t             *ip,
        xfs_dinode_t            *dip,
        xfs_inode_log_item_t    *iip,
        int                     whichfork)
{
        char                    *cp;
        xfs_ifork_t             *ifp;
        xfs_mount_t             *mp;
        int                     error;
        static const short      brootflag[2] =
                { XFS_ILOG_DBROOT, XFS_ILOG_ABROOT };
        static const short      dataflag[2] =
                { XFS_ILOG_DDATA, XFS_ILOG_ADATA };
        static const short      extflag[2] =
                { XFS_ILOG_DEXT, XFS_ILOG_AEXT };

        if (!iip)
                return 0;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        /*
         * This can happen if we gave up in iformat in an error path,
         * for the attribute fork.
         */
        if (!ifp) {
                ASSERT(whichfork == XFS_ATTR_FORK);
                return 0;
        }
        cp = XFS_DFORK_PTR(dip, whichfork);
        mp = ip->i_mount;
        switch (XFS_IFORK_FORMAT(ip, whichfork)) {
        case XFS_DINODE_FMT_LOCAL:
                if (S_ISDIR(VFS_I(ip)->i_mode) && whichfork == XFS_DATA_FORK) {
                        error = xfs_dir2_sf_verify(mp,
                                        (struct xfs_dir2_sf_hdr *)ifp->if_u1.if_data,
                                        ifp->if_bytes);
                        if (error)
                                return error;
                }
                if ((iip->ili_fields & dataflag[whichfork]) &&
                    (ifp->if_bytes > 0)) {
                        ASSERT(ifp->if_u1.if_data != NULL);
                        ASSERT(ifp->if_bytes <= XFS_IFORK_SIZE(ip, whichfork));
                        memcpy(cp, ifp->if_u1.if_data, ifp->if_bytes);
                }
                break;

        case XFS_DINODE_FMT_EXTENTS:
                ASSERT((ifp->if_flags & XFS_IFEXTENTS) ||
                       !(iip->ili_fields & extflag[whichfork]));
                if ((iip->ili_fields & extflag[whichfork]) &&
                    (ifp->if_bytes > 0)) {
                        ASSERT(xfs_iext_get_ext(ifp, 0));
                        ASSERT(XFS_IFORK_NEXTENTS(ip, whichfork) > 0);
                        (void)xfs_iextents_copy(ip, (xfs_bmbt_rec_t *)cp,
                                whichfork);
                }
                break;

        case XFS_DINODE_FMT_BTREE:
                if ((iip->ili_fields & brootflag[whichfork]) &&
                    (ifp->if_broot_bytes > 0)) {
                        ASSERT(ifp->if_broot != NULL);
                        ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
                                XFS_IFORK_SIZE(ip, whichfork));
                        xfs_bmbt_to_bmdr(mp, ifp->if_broot, ifp->if_broot_bytes,
                                (xfs_bmdr_block_t *)cp,
                                XFS_DFORK_SIZE(dip, mp, whichfork));
                }
                break;

        case XFS_DINODE_FMT_DEV:
                if (iip->ili_fields & XFS_ILOG_DEV) {
                        ASSERT(whichfork == XFS_DATA_FORK);
                        xfs_dinode_put_rdev(dip, ip->i_df.if_u2.if_rdev);
                }
                break;

        case XFS_DINODE_FMT_UUID:
                if (iip->ili_fields & XFS_ILOG_UUID) {
                        ASSERT(whichfork == XFS_DATA_FORK);
                        memcpy(XFS_DFORK_DPTR(dip),
                               &ip->i_df.if_u2.if_uuid,
                               sizeof(uuid_t));
                }
                break;

        default:
                ASSERT(0);
                break;
        }
        return 0;
}

/*
 * Return a pointer to the extent record at file index idx.
 */
xfs_bmbt_rec_host_t *
xfs_iext_get_ext(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    idx)            /* index of target extent */
{
        ASSERT(idx >= 0);
        ASSERT(idx < xfs_iext_count(ifp));

        if ((ifp->if_flags & XFS_IFEXTIREC) && (idx == 0)) {
                return ifp->if_u1.if_ext_irec->er_extbuf;
        } else if (ifp->if_flags & XFS_IFEXTIREC) {
                xfs_ext_irec_t  *erp;           /* irec pointer */
                int             erp_idx = 0;    /* irec index */
                xfs_extnum_t    page_idx = idx; /* ext index in target list */

                erp = xfs_iext_idx_to_irec(ifp, &page_idx, &erp_idx, 0);
                return &erp->er_extbuf[page_idx];
        } else if (ifp->if_bytes) {
                return &ifp->if_u1.if_extents[idx];
        } else {
                return NULL;
        }
}

/* Convert bmap state flags to an inode fork. */
struct xfs_ifork *
xfs_iext_state_to_fork(
        struct xfs_inode        *ip,
        int                     state)
{
        if (state & BMAP_COWFORK)
                return ip->i_cowfp;
        else if (state & BMAP_ATTRFORK)
                return ip->i_afp;
        return &ip->i_df;
}

/*
 * Insert new item(s) into the extent records for incore inode
 * fork 'ifp'.  'count' new items are inserted at index 'idx'.
 */
void
xfs_iext_insert(
        xfs_inode_t     *ip,            /* incore inode pointer */
        xfs_extnum_t    idx,            /* starting index of new items */
        xfs_extnum_t    count,          /* number of inserted items */
        xfs_bmbt_irec_t *new,           /* items to insert */
        int             state)          /* type of extent conversion */
{
        xfs_ifork_t     *ifp = xfs_iext_state_to_fork(ip, state);
        xfs_extnum_t    i;              /* extent record index */

        trace_xfs_iext_insert(ip, idx, new, state, _RET_IP_);

        ASSERT(ifp->if_flags & XFS_IFEXTENTS);
        xfs_iext_add(ifp, idx, count);
        for (i = idx; i < idx + count; i++, new++)
                xfs_bmbt_set_all(xfs_iext_get_ext(ifp, i), new);
}

/*
 * This is called when the amount of space required for incore file
 * extents needs to be increased. The ext_diff parameter stores the
 * number of new extents being added and the idx parameter contains
 * the extent index where the new extents will be added. If the new
 * extents are being appended, then we just need to (re)allocate and
 * initialize the space. Otherwise, if the new extents are being
 * inserted into the middle of the existing entries, a bit more work
 * is required to make room for the new extents to be inserted. The
 * caller is responsible for filling in the new extent entries upon
 * return.
 */
void
xfs_iext_add(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    idx,            /* index to begin adding exts */
        int             ext_diff)       /* number of extents to add */
{
        int             byte_diff;      /* new bytes being added */
        int             new_size;       /* size of extents after adding */
        xfs_extnum_t    nextents;       /* number of extents in file */

        nextents = xfs_iext_count(ifp);
        ASSERT((idx >= 0) && (idx <= nextents));
        byte_diff = ext_diff * sizeof(xfs_bmbt_rec_t);
        new_size = ifp->if_bytes + byte_diff;
        /*
         * If the new number of extents (nextents + ext_diff)
         * fits inside the inode, then continue to use the inline
         * extent buffer.
         */
        if (nextents + ext_diff <= XFS_INLINE_EXTS) {
                if (idx < nextents) {
                        memmove(&ifp->if_u2.if_inline_ext[idx + ext_diff],
                                &ifp->if_u2.if_inline_ext[idx],
                                (nextents - idx) * sizeof(xfs_bmbt_rec_t));
                        memset(&ifp->if_u2.if_inline_ext[idx], 0, byte_diff);
                }
                ifp->if_u1.if_extents = ifp->if_u2.if_inline_ext;
                ifp->if_real_bytes = 0;
        }
        /*
         * Otherwise use a linear (direct) extent list.
         * If the extents are currently inside the inode,
         * xfs_iext_realloc_direct will switch us from
         * inline to direct extent allocation mode.
         */
        else if (nextents + ext_diff <= XFS_LINEAR_EXTS) {
                xfs_iext_realloc_direct(ifp, new_size);
                if (idx < nextents) {
                        memmove(&ifp->if_u1.if_extents[idx + ext_diff],
                                &ifp->if_u1.if_extents[idx],
                                (nextents - idx) * sizeof(xfs_bmbt_rec_t));
                        memset(&ifp->if_u1.if_extents[idx], 0, byte_diff);
                }
        }
        /* Indirection array */
        else {
                xfs_ext_irec_t  *erp;
                int             erp_idx = 0;
                int             page_idx = idx;

                ASSERT(nextents + ext_diff > XFS_LINEAR_EXTS);
                if (ifp->if_flags & XFS_IFEXTIREC) {
                        erp = xfs_iext_idx_to_irec(ifp, &page_idx, &erp_idx, 1);
                } else {
                        xfs_iext_irec_init(ifp);
                        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
                        erp = ifp->if_u1.if_ext_irec;
                }
                /* Extents fit in target extent page */
                if (erp && erp->er_extcount + ext_diff <= XFS_LINEAR_EXTS) {
                        if (page_idx < erp->er_extcount) {
                                memmove(&erp->er_extbuf[page_idx + ext_diff],
                                        &erp->er_extbuf[page_idx],
                                        (erp->er_extcount - page_idx) *
                                        sizeof(xfs_bmbt_rec_t));
                                memset(&erp->er_extbuf[page_idx], 0, byte_diff);
                        }
                        erp->er_extcount += ext_diff;
                        xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
                }
                /* Insert a new extent page */
                else if (erp) {
                        xfs_iext_add_indirect_multi(ifp,
                                erp_idx, page_idx, ext_diff);
                }
                /*
                 * If extent(s) are being appended to the last page in
                 * the indirection array and the new extent(s) don't fit
                 * in the page, then erp is NULL and erp_idx is set to
                 * the next index needed in the indirection array.
                 */
                else {
                        uint    count = ext_diff;

                        while (count) {
                                erp = xfs_iext_irec_new(ifp, erp_idx);
                                erp->er_extcount = min(count, XFS_LINEAR_EXTS);
                                count -= erp->er_extcount;
                                if (count)
                                        erp_idx++;
                        }
                }
        }
        ifp->if_bytes = new_size;
}

/*
 * This is called when incore extents are being added to the indirection
 * array and the new extents do not fit in the target extent list. The
 * erp_idx parameter contains the irec index for the target extent list
 * in the indirection array, and the idx parameter contains the extent
 * index within the list. The number of extents being added is stored
 * in the count parameter.
 *
 *    |-------|   |-------|
 *    |       |   |       |    idx - number of extents before idx
 *    |  idx  |   | count |
 *    |       |   |       |    count - number of extents being inserted at idx
 *    |-------|   |-------|
 *    | count |   | nex2  |    nex2 - number of extents after idx + count
 *    |-------|   |-------|
 */
void
xfs_iext_add_indirect_multi(
        xfs_ifork_t     *ifp,                   /* inode fork pointer */
        int             erp_idx,                /* target extent irec index */
        xfs_extnum_t    idx,                    /* index within target list */
        int             count)                  /* new extents being added */
{
        int             byte_diff;              /* new bytes being added */
        xfs_ext_irec_t  *erp;                   /* pointer to irec entry */
        xfs_extnum_t    ext_diff;               /* number of extents to add */
        xfs_extnum_t    ext_cnt;                /* new extents still needed */
        xfs_extnum_t    nex2;                   /* extents after idx + count */
        xfs_bmbt_rec_t  *nex2_ep = NULL;        /* temp list for nex2 extents */
        int             nlists;                 /* number of irec's (lists) */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        erp = &ifp->if_u1.if_ext_irec[erp_idx];
        nex2 = erp->er_extcount - idx;
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;

        /*
         * Save second part of target extent list
         * (all extents past */
        if (nex2) {
                byte_diff = nex2 * sizeof(xfs_bmbt_rec_t);
                nex2_ep = (xfs_bmbt_rec_t *) kmem_alloc(byte_diff, KM_NOFS);
                memmove(nex2_ep, &erp->er_extbuf[idx], byte_diff);
                erp->er_extcount -= nex2;
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, -nex2);
                memset(&erp->er_extbuf[idx], 0, byte_diff);
        }

        /*
         * Add the new extents to the end of the target
         * list, then allocate new irec record(s) and
         * extent buffer(s) as needed to store the rest
         * of the new extents.
         */
        ext_cnt = count;
        ext_diff = MIN(ext_cnt, (int)XFS_LINEAR_EXTS - erp->er_extcount);
        if (ext_diff) {
                erp->er_extcount += ext_diff;
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
                ext_cnt -= ext_diff;
        }
        while (ext_cnt) {
                erp_idx++;
                erp = xfs_iext_irec_new(ifp, erp_idx);
                ext_diff = MIN(ext_cnt, (int)XFS_LINEAR_EXTS);
                erp->er_extcount = ext_diff;
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
                ext_cnt -= ext_diff;
        }

        /* Add nex2 extents back to indirection array */
        if (nex2) {
                xfs_extnum_t    ext_avail;
                int             i;

                byte_diff = nex2 * sizeof(xfs_bmbt_rec_t);
                ext_avail = XFS_LINEAR_EXTS - erp->er_extcount;
                i = 0;
                /*
                 * If nex2 extents fit in the current page, append
                 * nex2_ep after the new extents.
                 */
                if (nex2 <= ext_avail) {
                        i = erp->er_extcount;
                }
                /*
                 * Otherwise, check if space is available in the
                 * next page.
                 */
                else if ((erp_idx < nlists - 1) &&
                         (nex2 <= (ext_avail = XFS_LINEAR_EXTS -
                          ifp->if_u1.if_ext_irec[erp_idx+1].er_extcount))) {
                        erp_idx++;
                        erp++;
                        /* Create a hole for nex2 extents */
                        memmove(&erp->er_extbuf[nex2], erp->er_extbuf,
                                erp->er_extcount * sizeof(xfs_bmbt_rec_t));
                }
                /*
                 * Final choice, create a new extent page for
                 * nex2 extents.
                 */
                else {
                        erp_idx++;
                        erp = xfs_iext_irec_new(ifp, erp_idx);
                }
                memmove(&erp->er_extbuf[i], nex2_ep, byte_diff);
                kmem_free(nex2_ep);
                erp->er_extcount += nex2;
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, nex2);
        }
}

/*
 * This is called when the amount of space required for incore file
 * extents needs to be decreased. The ext_diff parameter stores the
 * number of extents to be removed and the idx parameter contains
 * the extent index where the extents will be removed from.
 *
 * If the amount of space needed has decreased below the linear
 * limit, XFS_IEXT_BUFSZ, then switch to using the contiguous
 * extent array.  Otherwise, use kmem_realloc() to adjust the
 * size to what is needed.
 */
void
xfs_iext_remove(
        xfs_inode_t     *ip,            /* incore inode pointer */
        xfs_extnum_t    idx,            /* index to begin removing exts */
        int             ext_diff,       /* number of extents to remove */
        int             state)          /* type of extent conversion */
{
        xfs_ifork_t     *ifp = xfs_iext_state_to_fork(ip, state);
        xfs_extnum_t    nextents;       /* number of extents in file */
        int             new_size;       /* size of extents after removal */

        trace_xfs_iext_remove(ip, idx, state, _RET_IP_);

        ASSERT(ext_diff > 0);
        nextents = xfs_iext_count(ifp);
        new_size = (nextents - ext_diff) * sizeof(xfs_bmbt_rec_t);

        if (new_size == 0) {
                xfs_iext_destroy(ifp);
        } else if (ifp->if_flags & XFS_IFEXTIREC) {
                xfs_iext_remove_indirect(ifp, idx, ext_diff);
        } else if (ifp->if_real_bytes) {
                xfs_iext_remove_direct(ifp, idx, ext_diff);
        } else {
                xfs_iext_remove_inline(ifp, idx, ext_diff);
        }
        ifp->if_bytes = new_size;
}

/*
 * This removes ext_diff extents from the inline buffer, beginning
 * at extent index idx.
 */
void
xfs_iext_remove_inline(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    idx,            /* index to begin removing exts */
        int             ext_diff)       /* number of extents to remove */
{
        int             nextents;       /* number of extents in file */

        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
        ASSERT(idx < XFS_INLINE_EXTS);
        nextents = xfs_iext_count(ifp);
        ASSERT(((nextents - ext_diff) > 0) &&
                (nextents - ext_diff) < XFS_INLINE_EXTS);

        if (idx + ext_diff < nextents) {
                memmove(&ifp->if_u2.if_inline_ext[idx],
                        &ifp->if_u2.if_inline_ext[idx + ext_diff],
                        (nextents - (idx + ext_diff)) *
                         sizeof(xfs_bmbt_rec_t));
                memset(&ifp->if_u2.if_inline_ext[nextents - ext_diff],
                        0, ext_diff * sizeof(xfs_bmbt_rec_t));
        } else {
                memset(&ifp->if_u2.if_inline_ext[idx], 0,
                        ext_diff * sizeof(xfs_bmbt_rec_t));
        }
}

/*
 * This removes ext_diff extents from a linear (direct) extent list,
 * beginning at extent index idx. If the extents are being removed
 * from the end of the list (ie. truncate) then we just need to re-
 * allocate the list to remove the extra space. Otherwise, if the
 * extents are being removed from the middle of the existing extent
 * entries, then we first need to move the extent records beginning
 * at idx + ext_diff up in the list to overwrite the records being
 * removed, then remove the extra space via kmem_realloc.
 */
void
xfs_iext_remove_direct(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    idx,            /* index to begin removing exts */
        int             ext_diff)       /* number of extents to remove */
{
        xfs_extnum_t    nextents;       /* number of extents in file */
        int             new_size;       /* size of extents after removal */

        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
        new_size = ifp->if_bytes -
                (ext_diff * sizeof(xfs_bmbt_rec_t));
        nextents = xfs_iext_count(ifp);

        if (new_size == 0) {
                xfs_iext_destroy(ifp);
                return;
        }
        /* Move extents up in the list (if needed) */
        if (idx + ext_diff < nextents) {
                memmove(&ifp->if_u1.if_extents[idx],
                        &ifp->if_u1.if_extents[idx + ext_diff],
                        (nextents - (idx + ext_diff)) *
                         sizeof(xfs_bmbt_rec_t));
        }
        memset(&ifp->if_u1.if_extents[nextents - ext_diff],
                0, ext_diff * sizeof(xfs_bmbt_rec_t));
        /*
         * Reallocate the direct extent list. If the extents
         * will fit inside the inode then xfs_iext_realloc_direct
         * will switch from direct to inline extent allocation
         * mode for us.
         */
        xfs_iext_realloc_direct(ifp, new_size);
        ifp->if_bytes = new_size;
}

/*
 * This is called when incore extents are being removed from the
 * indirection array and the extents being removed span multiple extent
 * buffers. The idx parameter contains the file extent index where we
 * want to begin removing extents, and the count parameter contains
 * how many extents need to be removed.
 *
 *    |-------|   |-------|
 *    | nex1  |   |       |    nex1 - number of extents before idx
 *    |-------|   | count |
 *    |       |   |       |    count - number of extents being removed at idx
 *    | count |   |-------|
 *    |       |   | nex2  |    nex2 - number of extents after idx + count
 *    |-------|   |-------|
 */
void
xfs_iext_remove_indirect(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    idx,            /* index to begin removing extents */
        int             count)          /* number of extents to remove */
{
        xfs_ext_irec_t  *erp;           /* indirection array pointer */
        int             erp_idx = 0;    /* indirection array index */
        xfs_extnum_t    ext_cnt;        /* extents left to remove */
        xfs_extnum_t    ext_diff;       /* extents to remove in current list */
        xfs_extnum_t    nex1;           /* number of extents before idx */
        xfs_extnum_t    nex2;           /* extents after idx + count */
        int             page_idx = idx; /* index in target extent list */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        erp = xfs_iext_idx_to_irec(ifp,  &page_idx, &erp_idx, 0);
        ASSERT(erp != NULL);
        nex1 = page_idx;
        ext_cnt = count;
        while (ext_cnt) {
                nex2 = MAX((erp->er_extcount - (nex1 + ext_cnt)), 0);
                ext_diff = MIN(ext_cnt, (erp->er_extcount - nex1));
                /*
                 * Check for deletion of entire list;
                 * xfs_iext_irec_remove() updates extent offsets.
                 */
                if (ext_diff == erp->er_extcount) {
                        xfs_iext_irec_remove(ifp, erp_idx);
                        ext_cnt -= ext_diff;
                        nex1 = 0;
                        if (ext_cnt) {
                                ASSERT(erp_idx < ifp->if_real_bytes /
                                        XFS_IEXT_BUFSZ);
                                erp = &ifp->if_u1.if_ext_irec[erp_idx];
                                nex1 = 0;
                                continue;
                        } else {
                                break;
                        }
                }
                /* Move extents up (if needed) */
                if (nex2) {
                        memmove(&erp->er_extbuf[nex1],
                                &erp->er_extbuf[nex1 + ext_diff],
                                nex2 * sizeof(xfs_bmbt_rec_t));
                }
                /* Zero out rest of page */
                memset(&erp->er_extbuf[nex1 + nex2], 0, (XFS_IEXT_BUFSZ -
                        ((nex1 + nex2) * sizeof(xfs_bmbt_rec_t))));
                /* Update remaining counters */
                erp->er_extcount -= ext_diff;
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, -ext_diff);
                ext_cnt -= ext_diff;
                nex1 = 0;
                erp_idx++;
                erp++;
        }
        ifp->if_bytes -= count * sizeof(xfs_bmbt_rec_t);
        xfs_iext_irec_compact(ifp);
}

/*
 * Create, destroy, or resize a linear (direct) block of extents.
 */
void
xfs_iext_realloc_direct(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             new_size)       /* new size of extents after adding */
{
        int             rnew_size;      /* real new size of extents */

        rnew_size = new_size;

        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC) ||
                ((new_size >= 0) && (new_size <= XFS_IEXT_BUFSZ) &&
                 (new_size != ifp->if_real_bytes)));

        /* Free extent records */
        if (new_size == 0) {
                xfs_iext_destroy(ifp);
        }
        /* Resize direct extent list and zero any new bytes */
        else if (ifp->if_real_bytes) {
                /* Check if extents will fit inside the inode */
                if (new_size <= XFS_INLINE_EXTS * sizeof(xfs_bmbt_rec_t)) {
                        xfs_iext_direct_to_inline(ifp, new_size /
                                (uint)sizeof(xfs_bmbt_rec_t));
                        ifp->if_bytes = new_size;
                        return;
                }
                if (!is_power_of_2(new_size)){
                        rnew_size = roundup_pow_of_two(new_size);
                }
                if (rnew_size != ifp->if_real_bytes) {
                        ifp->if_u1.if_extents =
                                kmem_realloc(ifp->if_u1.if_extents,
                                                rnew_size, KM_NOFS);
                }
                if (rnew_size > ifp->if_real_bytes) {
                        memset(&ifp->if_u1.if_extents[ifp->if_bytes /
                                (uint)sizeof(xfs_bmbt_rec_t)], 0,
                                rnew_size - ifp->if_real_bytes);
                }
        }
        /* Switch from the inline extent buffer to a direct extent list */
        else {
                if (!is_power_of_2(new_size)) {
                        rnew_size = roundup_pow_of_two(new_size);
                }
                xfs_iext_inline_to_direct(ifp, rnew_size);
        }
        ifp->if_real_bytes = rnew_size;
        ifp->if_bytes = new_size;
}

/*
 * Switch from linear (direct) extent records to inline buffer.
 */
void
xfs_iext_direct_to_inline(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    nextents)       /* number of extents in file */
{
        ASSERT(ifp->if_flags & XFS_IFEXTENTS);
        ASSERT(nextents <= XFS_INLINE_EXTS);
        /*
         * The inline buffer was zeroed when we switched
         * from inline to direct extent allocation mode,
         * so we don't need to clear it here.
         */
        memcpy(ifp->if_u2.if_inline_ext, ifp->if_u1.if_extents,
                nextents * sizeof(xfs_bmbt_rec_t));
        kmem_free(ifp->if_u1.if_extents);
        ifp->if_u1.if_extents = ifp->if_u2.if_inline_ext;
        ifp->if_real_bytes = 0;
}

/*
 * Switch from inline buffer to linear (direct) extent records.
 * new_size should already be rounded up to the next power of 2
 * by the caller (when appropriate), so use new_size as it is.
 * However, since new_size may be rounded up, we can't update
 * if_bytes here. It is the caller's responsibility to update
 * if_bytes upon return.
 */
void
xfs_iext_inline_to_direct(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             new_size)       /* number of extents in file */
{
        ifp->if_u1.if_extents = kmem_alloc(new_size, KM_NOFS);
        memset(ifp->if_u1.if_extents, 0, new_size);
        if (ifp->if_bytes) {
                memcpy(ifp->if_u1.if_extents, ifp->if_u2.if_inline_ext,
                        ifp->if_bytes);
                memset(ifp->if_u2.if_inline_ext, 0, XFS_INLINE_EXTS *
                        sizeof(xfs_bmbt_rec_t));
        }
        ifp->if_real_bytes = new_size;
}

/*
 * Resize an extent indirection array to new_size bytes.
 */
STATIC void
xfs_iext_realloc_indirect(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             new_size)       /* new indirection array size */
{
#ifdef DEBUG
        int             nlists;         /* number of irec's (ex lists) */
        int             size;           /* current indirection array size */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        size = nlists * sizeof(xfs_ext_irec_t);
        ASSERT(ifp->if_real_bytes);
        ASSERT((new_size >= 0) && (new_size != size));
#endif
        if (new_size == 0) {
                xfs_iext_destroy(ifp);
        } else {
                ifp->if_u1.if_ext_irec =
                        kmem_realloc(ifp->if_u1.if_ext_irec, new_size, KM_NOFS);
        }
}

/*
 * Switch from indirection array to linear (direct) extent allocations.
 */
STATIC void
xfs_iext_indirect_to_direct(
         xfs_ifork_t    *ifp)           /* inode fork pointer */
{
        xfs_bmbt_rec_host_t *ep;        /* extent record pointer */
        xfs_extnum_t    nextents;       /* number of extents in file */
        int             size;           /* size of file extents */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nextents = xfs_iext_count(ifp);
        ASSERT(nextents <= XFS_LINEAR_EXTS);
        size = nextents * sizeof(xfs_bmbt_rec_t);

        xfs_iext_irec_compact_pages(ifp);
        ASSERT(ifp->if_real_bytes == XFS_IEXT_BUFSZ);

        ep = ifp->if_u1.if_ext_irec->er_extbuf;
        kmem_free(ifp->if_u1.if_ext_irec);
        ifp->if_flags &= ~XFS_IFEXTIREC;
        ifp->if_u1.if_extents = ep;
        ifp->if_bytes = size;
        if (nextents < XFS_LINEAR_EXTS) {
                xfs_iext_realloc_direct(ifp, size);
        }
}

/*
 * Remove all records from the indirection array.
 */
STATIC void
xfs_iext_irec_remove_all(
        struct xfs_ifork *ifp)
{
        int             nlists;
        int             i;

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        for (i = 0; i < nlists; i++)
                kmem_free(ifp->if_u1.if_ext_irec[i].er_extbuf);
        kmem_free(ifp->if_u1.if_ext_irec);
        ifp->if_flags &= ~XFS_IFEXTIREC;
}

/*
 * Free incore file extents.
 */
void
xfs_iext_destroy(
        xfs_ifork_t     *ifp)           /* inode fork pointer */
{
        if (ifp->if_flags & XFS_IFEXTIREC) {
                xfs_iext_irec_remove_all(ifp);
        } else if (ifp->if_real_bytes) {
                kmem_free(ifp->if_u1.if_extents);
        } else if (ifp->if_bytes) {
                memset(ifp->if_u2.if_inline_ext, 0, XFS_INLINE_EXTS *
                        sizeof(xfs_bmbt_rec_t));
        }
        ifp->if_u1.if_extents = NULL;
        ifp->if_real_bytes = 0;
        ifp->if_bytes = 0;
}

/*
 * Return a pointer to the extent record for file system block bno.
 */
xfs_bmbt_rec_host_t *                   /* pointer to found extent record */
xfs_iext_bno_to_ext(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_fileoff_t   bno,            /* block number to search for */
        xfs_extnum_t    *idxp)          /* index of target extent */
{
        xfs_bmbt_rec_host_t *base;      /* pointer to first extent */
        xfs_filblks_t   blockcount = 0; /* number of blocks in extent */
        xfs_bmbt_rec_host_t *ep = NULL; /* pointer to target extent */
        xfs_ext_irec_t  *erp = NULL;    /* indirection array pointer */
        int             high;           /* upper boundary in search */
        xfs_extnum_t    idx = 0;        /* index of target extent */
        int             low;            /* lower boundary in search */
        xfs_extnum_t    nextents;       /* number of file extents */
        xfs_fileoff_t   startoff = 0;   /* start offset of extent */

        nextents = xfs_iext_count(ifp);
        if (nextents == 0) {
                *idxp = 0;
                return NULL;
        }
        low = 0;
        if (ifp->if_flags & XFS_IFEXTIREC) {
                /* Find target extent list */
                int     erp_idx = 0;
                erp = xfs_iext_bno_to_irec(ifp, bno, &erp_idx);
                base = erp->er_extbuf;
                high = erp->er_extcount - 1;
        } else {
                base = ifp->if_u1.if_extents;
                high = nextents - 1;
        }
        /* Binary search extent records */
        while (low <= high) {
                idx = (low + high) >> 1;
                ep = base + idx;
                startoff = xfs_bmbt_get_startoff(ep);
                blockcount = xfs_bmbt_get_blockcount(ep);
                if (bno < startoff) {
                        high = idx - 1;
                } else if (bno >= startoff + blockcount) {
                        low = idx + 1;
                } else {
                        /* Convert back to file-based extent index */
                        if (ifp->if_flags & XFS_IFEXTIREC) {
                                idx += erp->er_extoff;
                        }
                        *idxp = idx;
                        return ep;
                }
        }
        /* Convert back to file-based extent index */
        if (ifp->if_flags & XFS_IFEXTIREC) {
                idx += erp->er_extoff;
        }
        if (bno >= startoff + blockcount) {
                if (++idx == nextents) {
                        ep = NULL;
                } else {
                        ep = xfs_iext_get_ext(ifp, idx);
                }
        }
        *idxp = idx;
        return ep;
}

/*
 * Return a pointer to the indirection array entry containing the
 * extent record for filesystem block bno. Store the index of the
 * target irec in *erp_idxp.
 */
xfs_ext_irec_t *                        /* pointer to found extent record */
xfs_iext_bno_to_irec(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_fileoff_t   bno,            /* block number to search for */
        int             *erp_idxp)      /* irec index of target ext list */
{
        xfs_ext_irec_t  *erp = NULL;    /* indirection array pointer */
        xfs_ext_irec_t  *erp_next;      /* next indirection array entry */
        int             erp_idx;        /* indirection array index */
        int             nlists;         /* number of extent irec's (lists) */
        int             high;           /* binary search upper limit */
        int             low;            /* binary search lower limit */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        erp_idx = 0;
        low = 0;
        high = nlists - 1;
        while (low <= high) {
                erp_idx = (low + high) >> 1;
                erp = &ifp->if_u1.if_ext_irec[erp_idx];
                erp_next = erp_idx < nlists - 1 ? erp + 1 : NULL;
                if (bno < xfs_bmbt_get_startoff(erp->er_extbuf)) {
                        high = erp_idx - 1;
                } else if (erp_next && bno >=
                           xfs_bmbt_get_startoff(erp_next->er_extbuf)) {
                        low = erp_idx + 1;
                } else {
                        break;
                }
        }
        *erp_idxp = erp_idx;
        return erp;
}

/*
 * Return a pointer to the indirection array entry containing the
 * extent record at file extent index *idxp. Store the index of the
 * target irec in *erp_idxp and store the page index of the target
 * extent record in *idxp.
 */
xfs_ext_irec_t *
xfs_iext_idx_to_irec(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_extnum_t    *idxp,          /* extent index (file -> page) */
        int             *erp_idxp,      /* pointer to target irec */
        int             realloc)        /* new bytes were just added */
{
        xfs_ext_irec_t  *prev;          /* pointer to previous irec */
        xfs_ext_irec_t  *erp = NULL;    /* pointer to current irec */
        int             erp_idx;        /* indirection array index */
        int             nlists;         /* number of irec's (ex lists) */
        int             high;           /* binary search upper limit */
        int             low;            /* binary search lower limit */
        xfs_extnum_t    page_idx = *idxp; /* extent index in target list */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        ASSERT(page_idx >= 0);
        ASSERT(page_idx <= xfs_iext_count(ifp));
        ASSERT(page_idx < xfs_iext_count(ifp) || realloc);

        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        erp_idx = 0;
        low = 0;
        high = nlists - 1;

        /* Binary search extent irec's */
        while (low <= high) {
                erp_idx = (low + high) >> 1;
                erp = &ifp->if_u1.if_ext_irec[erp_idx];
                prev = erp_idx > 0 ? erp - 1 : NULL;
                if (page_idx < erp->er_extoff || (page_idx == erp->er_extoff &&
                     realloc && prev && prev->er_extcount < XFS_LINEAR_EXTS)) {
                        high = erp_idx - 1;
                } else if (page_idx > erp->er_extoff + erp->er_extcount ||
                           (page_idx == erp->er_extoff + erp->er_extcount &&
                            !realloc)) {
                        low = erp_idx + 1;
                } else if (page_idx == erp->er_extoff + erp->er_extcount &&
                           erp->er_extcount == XFS_LINEAR_EXTS) {
                        ASSERT(realloc);
                        page_idx = 0;
                        erp_idx++;
                        erp = erp_idx < nlists ? erp + 1 : NULL;
                        break;
                } else {
                        page_idx -= erp->er_extoff;
                        break;
                }
        }
        *idxp = page_idx;
        *erp_idxp = erp_idx;
        return erp;
}

/*
 * Allocate and initialize an indirection array once the space needed
 * for incore extents increases above XFS_IEXT_BUFSZ.
 */
void
xfs_iext_irec_init(
        xfs_ifork_t     *ifp)           /* inode fork pointer */
{
        xfs_ext_irec_t  *erp;           /* indirection array pointer */
        xfs_extnum_t    nextents;       /* number of extents in file */

        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
        nextents = xfs_iext_count(ifp);
        ASSERT(nextents <= XFS_LINEAR_EXTS);

        erp = kmem_alloc(sizeof(xfs_ext_irec_t), KM_NOFS);

        if (nextents == 0) {
                ifp->if_u1.if_extents = kmem_alloc(XFS_IEXT_BUFSZ, KM_NOFS);
        } else if (!ifp->if_real_bytes) {
                xfs_iext_inline_to_direct(ifp, XFS_IEXT_BUFSZ);
        } else if (ifp->if_real_bytes < XFS_IEXT_BUFSZ) {
                xfs_iext_realloc_direct(ifp, XFS_IEXT_BUFSZ);
        }
        erp->er_extbuf = ifp->if_u1.if_extents;
        erp->er_extcount = nextents;
        erp->er_extoff = 0;

        ifp->if_flags |= XFS_IFEXTIREC;
        ifp->if_real_bytes = XFS_IEXT_BUFSZ;
        ifp->if_bytes = nextents * sizeof(xfs_bmbt_rec_t);
        ifp->if_u1.if_ext_irec = erp;

        return;
}

/*
 * Allocate and initialize a new entry in the indirection array.
 */
xfs_ext_irec_t *
xfs_iext_irec_new(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             erp_idx)        /* index for new irec */
{
        xfs_ext_irec_t  *erp;           /* indirection array pointer */
        int             i;              /* loop counter */
        int             nlists;         /* number of irec's (ex lists) */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;

        /* Resize indirection array */
        xfs_iext_realloc_indirect(ifp, ++nlists *
                                  sizeof(xfs_ext_irec_t));
        /*
         * Move records down in the array so the
         * new page can use erp_idx.
         */
        erp = ifp->if_u1.if_ext_irec;
        for (i = nlists - 1; i > erp_idx; i--) {
                memmove(&erp[i], &erp[i-1], sizeof(xfs_ext_irec_t));
        }
        ASSERT(i == erp_idx);

        /* Initialize new extent record */
        erp = ifp->if_u1.if_ext_irec;
        erp[erp_idx].er_extbuf = kmem_alloc(XFS_IEXT_BUFSZ, KM_NOFS);
        ifp->if_real_bytes = nlists * XFS_IEXT_BUFSZ;
        memset(erp[erp_idx].er_extbuf, 0, XFS_IEXT_BUFSZ);
        erp[erp_idx].er_extcount = 0;
        erp[erp_idx].er_extoff = erp_idx > 0 ?
                erp[erp_idx-1].er_extoff + erp[erp_idx-1].er_extcount : 0;
        return (&erp[erp_idx]);
}

/*
 * Remove a record from the indirection array.
 */
void
xfs_iext_irec_remove(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             erp_idx)        /* irec index to remove */
{
        xfs_ext_irec_t  *erp;           /* indirection array pointer */
        int             i;              /* loop counter */
        int             nlists;         /* number of irec's (ex lists) */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        erp = &ifp->if_u1.if_ext_irec[erp_idx];
        if (erp->er_extbuf) {
                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1,
                        -erp->er_extcount);
                kmem_free(erp->er_extbuf);
        }
        /* Compact extent records */
        erp = ifp->if_u1.if_ext_irec;
        for (i = erp_idx; i < nlists - 1; i++) {
                memmove(&erp[i], &erp[i+1], sizeof(xfs_ext_irec_t));
        }
        /*
         * Manually free the last extent record from the indirection
         * array.  A call to xfs_iext_realloc_indirect() with a size
         * of zero would result in a call to xfs_iext_destroy() which
         * would in turn call this function again, creating a nasty
         * infinite loop.
         */
        if (--nlists) {
                xfs_iext_realloc_indirect(ifp,
                        nlists * sizeof(xfs_ext_irec_t));
        } else {
                kmem_free(ifp->if_u1.if_ext_irec);
        }
        ifp->if_real_bytes = nlists * XFS_IEXT_BUFSZ;
}

/*
 * This is called to clean up large amounts of unused memory allocated
 * by the indirection array.  Before compacting anything though, verify
 * that the indirection array is still needed and switch back to the
 * linear extent list (or even the inline buffer) if possible.  The
 * compaction policy is as follows:
 *
 *    Full Compaction: Extents fit into a single page (or inline buffer)
 * Partial Compaction: Extents occupy less than 50% of allocated space
 *      No Compaction: Extents occupy at least 50% of allocated space
 */
void
xfs_iext_irec_compact(
        xfs_ifork_t     *ifp)           /* inode fork pointer */
{
        xfs_extnum_t    nextents;       /* number of extents in file */
        int             nlists;         /* number of irec's (ex lists) */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        nextents = xfs_iext_count(ifp);

        if (nextents == 0) {
                xfs_iext_destroy(ifp);
        } else if (nextents <= XFS_INLINE_EXTS) {
                xfs_iext_indirect_to_direct(ifp);
                xfs_iext_direct_to_inline(ifp, nextents);
        } else if (nextents <= XFS_LINEAR_EXTS) {
                xfs_iext_indirect_to_direct(ifp);
        } else if (nextents < (nlists * XFS_LINEAR_EXTS) >> 1) {
                xfs_iext_irec_compact_pages(ifp);
        }
}

/*
 * Combine extents from neighboring extent pages.
 */
void
xfs_iext_irec_compact_pages(
        xfs_ifork_t     *ifp)           /* inode fork pointer */
{
        xfs_ext_irec_t  *erp, *erp_next;/* pointers to irec entries */
        int             erp_idx = 0;    /* indirection array index */
        int             nlists;         /* number of irec's (ex lists) */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        while (erp_idx < nlists - 1) {
                erp = &ifp->if_u1.if_ext_irec[erp_idx];
                erp_next = erp + 1;
                if (erp_next->er_extcount <=
                    (XFS_LINEAR_EXTS - erp->er_extcount)) {
                        memcpy(&erp->er_extbuf[erp->er_extcount],
                                erp_next->er_extbuf, erp_next->er_extcount *
                                sizeof(xfs_bmbt_rec_t));
                        erp->er_extcount += erp_next->er_extcount;
                        /*
                         * Free page before removing extent record
                         * so er_extoffs don't get modified in
                         * xfs_iext_irec_remove.
                         */
                        kmem_free(erp_next->er_extbuf);
                        erp_next->er_extbuf = NULL;
                        xfs_iext_irec_remove(ifp, erp_idx + 1);
                        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
                } else {
                        erp_idx++;
                }
        }
}

/*
 * This is called to update the er_extoff field in the indirection
 * array when extents have been added or removed from one of the
 * extent lists. erp_idx contains the irec index to begin updating
 * at and ext_diff contains the number of extents that were added
 * or removed.
 */
void
xfs_iext_irec_update_extoffs(
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        int             erp_idx,        /* irec index to update */
        int             ext_diff)       /* number of new extents */
{
        int             i;              /* loop counter */
        int             nlists;         /* number of irec's (ex lists */

        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
        for (i = erp_idx; i < nlists; i++) {
                ifp->if_u1.if_ext_irec[i].er_extoff += ext_diff;
        }
}

/*
 * Initialize an inode's copy-on-write fork.
 */
void
xfs_ifork_init_cow(
        struct xfs_inode        *ip)
{
        if (ip->i_cowfp)
                return;

        ip->i_cowfp = kmem_zone_zalloc(xfs_ifork_zone,
                                       KM_SLEEP | KM_NOFS);
        ip->i_cowfp->if_flags = XFS_IFEXTENTS;
        ip->i_cformat = XFS_DINODE_FMT_EXTENTS;
        ip->i_cnextents = 0;
}

/*
 * Lookup the extent covering bno.
 *
 * If there is an extent covering bno return the extent index, and store the
 * expanded extent structure in *gotp, and the extent index in *idx.
 * If there is no extent covering bno, but there is an extent after it (e.g.
 * it lies in a hole) return that extent in *gotp and its index in *idx
 * instead.
 * If bno is beyond the last extent return false, and return the index after
 * the last valid index in *idxp.
 */
bool
xfs_iext_lookup_extent(
        struct xfs_inode        *ip,
        struct xfs_ifork        *ifp,
        xfs_fileoff_t           bno,
        xfs_extnum_t            *idxp,
        struct xfs_bmbt_irec    *gotp)
{
        struct xfs_bmbt_rec_host *ep;

        XFS_STATS_INC(ip->i_mount, xs_look_exlist);

        ep = xfs_iext_bno_to_ext(ifp, bno, idxp);
        if (!ep)
                return false;
        xfs_bmbt_get_all(ep, gotp);
        return true;
}

/*
 * Return true if there is an extent at index idx, and return the expanded
 * extent structure at idx in that case.  Else return false.
 */
bool
xfs_iext_get_extent(
        struct xfs_ifork        *ifp,
        xfs_extnum_t            idx,
        struct xfs_bmbt_irec    *gotp)
{
        if (idx < 0 || idx >= xfs_iext_count(ifp))
                return false;
        xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), gotp);
        return true;
}