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

/*
 * Copyright (c) 2000-2003,2005 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_mount.h"
#include "xfs_defer.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_bmap.h"
#include "xfs_trace.h"
#include "xfs_cksum.h"
#include "xfs_rmap.h"

/*
 * Convert on-disk form of btree root to in-memory form.
 */
void
xfs_bmdr_to_bmbt(
        struct xfs_inode        *ip,
        xfs_bmdr_block_t        *dblock,
        int                     dblocklen,
        struct xfs_btree_block  *rblock,
        int                     rblocklen)
{
        struct xfs_mount        *mp = ip->i_mount;
        int                     dmxr;
        xfs_bmbt_key_t          *fkp;
        __be64                  *fpp;
        xfs_bmbt_key_t          *tkp;
        __be64                  *tpp;

        xfs_btree_init_block_int(mp, rblock, XFS_BUF_DADDR_NULL,
                                 XFS_BTNUM_BMAP, 0, 0, ip->i_ino,
                                 XFS_BTREE_LONG_PTRS);
        rblock->bb_level = dblock->bb_level;
        ASSERT(be16_to_cpu(rblock->bb_level) > 0);
        rblock->bb_numrecs = dblock->bb_numrecs;
        dmxr = xfs_bmdr_maxrecs(dblocklen, 0);
        fkp = XFS_BMDR_KEY_ADDR(dblock, 1);
        tkp = XFS_BMBT_KEY_ADDR(mp, rblock, 1);
        fpp = XFS_BMDR_PTR_ADDR(dblock, 1, dmxr);
        tpp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, rblocklen);
        dmxr = be16_to_cpu(dblock->bb_numrecs);
        memcpy(tkp, fkp, sizeof(*fkp) * dmxr);
        memcpy(tpp, fpp, sizeof(*fpp) * dmxr);
}

void
xfs_bmbt_disk_get_all(
        struct xfs_bmbt_rec     *rec,
        struct xfs_bmbt_irec    *irec)
{
        uint64_t                l0 = get_unaligned_be64(&rec->l0);
        uint64_t                l1 = get_unaligned_be64(&rec->l1);

        irec->br_startoff = (l0 & xfs_mask64lo(64 - BMBT_EXNTFLAG_BITLEN)) >> 9;
        irec->br_startblock = ((l0 & xfs_mask64lo(9)) << 43) | (l1 >> 21);
        irec->br_blockcount = l1 & xfs_mask64lo(21);
        if (l0 >> (64 - BMBT_EXNTFLAG_BITLEN))
                irec->br_state = XFS_EXT_UNWRITTEN;
        else
                irec->br_state = XFS_EXT_NORM;
}

/*
 * Extract the blockcount field from an on disk bmap extent record.
 */
xfs_filblks_t
xfs_bmbt_disk_get_blockcount(
        xfs_bmbt_rec_t  *r)
{
        return (xfs_filblks_t)(be64_to_cpu(r->l1) & xfs_mask64lo(21));
}

/*
 * Extract the startoff field from a disk format bmap extent record.
 */
xfs_fileoff_t
xfs_bmbt_disk_get_startoff(
        xfs_bmbt_rec_t  *r)
{
        return ((xfs_fileoff_t)be64_to_cpu(r->l0) &
                 xfs_mask64lo(64 - BMBT_EXNTFLAG_BITLEN)) >> 9;
}

/*
 * Set all the fields in a bmap extent record from the uncompressed form.
 */
void
xfs_bmbt_disk_set_all(
        struct xfs_bmbt_rec     *r,
        struct xfs_bmbt_irec    *s)
{
        int                     extent_flag = (s->br_state != XFS_EXT_NORM);

        ASSERT(s->br_state == XFS_EXT_NORM || s->br_state == XFS_EXT_UNWRITTEN);
        ASSERT(!(s->br_startoff & xfs_mask64hi(64-BMBT_STARTOFF_BITLEN)));
        ASSERT(!(s->br_blockcount & xfs_mask64hi(64-BMBT_BLOCKCOUNT_BITLEN)));
        ASSERT(!(s->br_startblock & xfs_mask64hi(64-BMBT_STARTBLOCK_BITLEN)));

        put_unaligned_be64(
                ((xfs_bmbt_rec_base_t)extent_flag << 63) |
                 ((xfs_bmbt_rec_base_t)s->br_startoff << 9) |
                 ((xfs_bmbt_rec_base_t)s->br_startblock >> 43), &r->l0);
        put_unaligned_be64(
                ((xfs_bmbt_rec_base_t)s->br_startblock << 21) |
                 ((xfs_bmbt_rec_base_t)s->br_blockcount &
                  (xfs_bmbt_rec_base_t)xfs_mask64lo(21)), &r->l1);
}

/*
 * Convert in-memory form of btree root to on-disk form.
 */
void
xfs_bmbt_to_bmdr(
        struct xfs_mount        *mp,
        struct xfs_btree_block  *rblock,
        int                     rblocklen,
        xfs_bmdr_block_t        *dblock,
        int                     dblocklen)
{
        int                     dmxr;
        xfs_bmbt_key_t          *fkp;
        __be64                  *fpp;
        xfs_bmbt_key_t          *tkp;
        __be64                  *tpp;

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                ASSERT(rblock->bb_magic == cpu_to_be32(XFS_BMAP_CRC_MAGIC));
                ASSERT(uuid_equal(&rblock->bb_u.l.bb_uuid,
                       &mp->m_sb.sb_meta_uuid));
                ASSERT(rblock->bb_u.l.bb_blkno ==
                       cpu_to_be64(XFS_BUF_DADDR_NULL));
        } else
                ASSERT(rblock->bb_magic == cpu_to_be32(XFS_BMAP_MAGIC));
        ASSERT(rblock->bb_u.l.bb_leftsib == cpu_to_be64(NULLFSBLOCK));
        ASSERT(rblock->bb_u.l.bb_rightsib == cpu_to_be64(NULLFSBLOCK));
        ASSERT(rblock->bb_level != 0);
        dblock->bb_level = rblock->bb_level;
        dblock->bb_numrecs = rblock->bb_numrecs;
        dmxr = xfs_bmdr_maxrecs(dblocklen, 0);
        fkp = XFS_BMBT_KEY_ADDR(mp, rblock, 1);
        tkp = XFS_BMDR_KEY_ADDR(dblock, 1);
        fpp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, rblocklen);
        tpp = XFS_BMDR_PTR_ADDR(dblock, 1, dmxr);
        dmxr = be16_to_cpu(dblock->bb_numrecs);
        memcpy(tkp, fkp, sizeof(*fkp) * dmxr);
        memcpy(tpp, fpp, sizeof(*fpp) * dmxr);
}

STATIC struct xfs_btree_cur *
xfs_bmbt_dup_cursor(
        struct xfs_btree_cur    *cur)
{
        struct xfs_btree_cur    *new;

        new = xfs_bmbt_init_cursor(cur->bc_mp, cur->bc_tp,
                        cur->bc_private.b.ip, cur->bc_private.b.whichfork);

        /*
         * Copy the firstblock, dfops, and flags values,
         * since init cursor doesn't get them.
         */
        new->bc_private.b.firstblock = cur->bc_private.b.firstblock;
        new->bc_private.b.dfops = cur->bc_private.b.dfops;
        new->bc_private.b.flags = cur->bc_private.b.flags;

        return new;
}

STATIC void
xfs_bmbt_update_cursor(
        struct xfs_btree_cur    *src,
        struct xfs_btree_cur    *dst)
{
        ASSERT((dst->bc_private.b.firstblock != NULLFSBLOCK) ||
               (dst->bc_private.b.ip->i_d.di_flags & XFS_DIFLAG_REALTIME));
        ASSERT(dst->bc_private.b.dfops == src->bc_private.b.dfops);

        dst->bc_private.b.allocated += src->bc_private.b.allocated;
        dst->bc_private.b.firstblock = src->bc_private.b.firstblock;

        src->bc_private.b.allocated = 0;
}

STATIC int
xfs_bmbt_alloc_block(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *start,
        union xfs_btree_ptr     *new,
        int                     *stat)
{
        xfs_alloc_arg_t         args;           /* block allocation args */
        int                     error;          /* error return value */

        memset(&args, 0, sizeof(args));
        args.tp = cur->bc_tp;
        args.mp = cur->bc_mp;
        args.fsbno = cur->bc_private.b.firstblock;
        args.firstblock = args.fsbno;
        xfs_rmap_ino_bmbt_owner(&args.oinfo, cur->bc_private.b.ip->i_ino,
                        cur->bc_private.b.whichfork);

        if (args.fsbno == NULLFSBLOCK) {
                args.fsbno = be64_to_cpu(start->l);
                args.type = XFS_ALLOCTYPE_START_BNO;
                /*
                 * Make sure there is sufficient room left in the AG to
                 * complete a full tree split for an extent insert.  If
                 * we are converting the middle part of an extent then
                 * we may need space for two tree splits.
                 *
                 * We are relying on the caller to make the correct block
                 * reservation for this operation to succeed.  If the
                 * reservation amount is insufficient then we may fail a
                 * block allocation here and corrupt the filesystem.
                 */
                args.minleft = args.tp->t_blk_res;
        } else if (cur->bc_private.b.dfops->dop_low) {
                args.type = XFS_ALLOCTYPE_START_BNO;
        } else {
                args.type = XFS_ALLOCTYPE_NEAR_BNO;
        }

        args.minlen = args.maxlen = args.prod = 1;
        args.wasdel = cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL;
        if (!args.wasdel && args.tp->t_blk_res == 0) {
                error = -ENOSPC;
                goto error0;
        }
        error = xfs_alloc_vextent(&args);
        if (error)
                goto error0;

        if (args.fsbno == NULLFSBLOCK && args.minleft) {
                /*
                 * Could not find an AG with enough free space to satisfy
                 * a full btree split.  Try again and if
                 * successful activate the lowspace algorithm.
                 */
                args.fsbno = 0;
                args.type = XFS_ALLOCTYPE_FIRST_AG;
                error = xfs_alloc_vextent(&args);
                if (error)
                        goto error0;
                cur->bc_private.b.dfops->dop_low = true;
        }
        if (WARN_ON_ONCE(args.fsbno == NULLFSBLOCK)) {
                *stat = 0;
                return 0;
        }

        ASSERT(args.len == 1);
        cur->bc_private.b.firstblock = args.fsbno;
        cur->bc_private.b.allocated++;
        cur->bc_private.b.ip->i_d.di_nblocks++;
        xfs_trans_log_inode(args.tp, cur->bc_private.b.ip, XFS_ILOG_CORE);
        xfs_trans_mod_dquot_byino(args.tp, cur->bc_private.b.ip,
                        XFS_TRANS_DQ_BCOUNT, 1L);

        new->l = cpu_to_be64(args.fsbno);

        *stat = 1;
        return 0;

 error0:
        return error;
}

STATIC int
xfs_bmbt_free_block(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = cur->bc_mp;
        struct xfs_inode        *ip = cur->bc_private.b.ip;
        struct xfs_trans        *tp = cur->bc_tp;
        xfs_fsblock_t           fsbno = XFS_DADDR_TO_FSB(mp, XFS_BUF_ADDR(bp));
        struct xfs_owner_info   oinfo;

        xfs_rmap_ino_bmbt_owner(&oinfo, ip->i_ino, cur->bc_private.b.whichfork);
        xfs_bmap_add_free(mp, cur->bc_private.b.dfops, fsbno, 1, &oinfo);
        ip->i_d.di_nblocks--;

        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
        xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, -1L);
        return 0;
}

STATIC int
xfs_bmbt_get_minrecs(
        struct xfs_btree_cur    *cur,
        int                     level)
{
        if (level == cur->bc_nlevels - 1) {
                struct xfs_ifork        *ifp;

                ifp = XFS_IFORK_PTR(cur->bc_private.b.ip,
                                    cur->bc_private.b.whichfork);

                return xfs_bmbt_maxrecs(cur->bc_mp,
                                        ifp->if_broot_bytes, level == 0) / 2;
        }

        return cur->bc_mp->m_bmap_dmnr[level != 0];
}

int
xfs_bmbt_get_maxrecs(
        struct xfs_btree_cur    *cur,
        int                     level)
{
        if (level == cur->bc_nlevels - 1) {
                struct xfs_ifork        *ifp;

                ifp = XFS_IFORK_PTR(cur->bc_private.b.ip,
                                    cur->bc_private.b.whichfork);

                return xfs_bmbt_maxrecs(cur->bc_mp,
                                        ifp->if_broot_bytes, level == 0);
        }

        return cur->bc_mp->m_bmap_dmxr[level != 0];

}

/*
 * Get the maximum records we could store in the on-disk format.
 *
 * For non-root nodes this is equivalent to xfs_bmbt_get_maxrecs, but
 * for the root node this checks the available space in the dinode fork
 * so that we can resize the in-memory buffer to match it.  After a
 * resize to the maximum size this function returns the same value
 * as xfs_bmbt_get_maxrecs for the root node, too.
 */
STATIC int
xfs_bmbt_get_dmaxrecs(
        struct xfs_btree_cur    *cur,
        int                     level)
{
        if (level != cur->bc_nlevels - 1)
                return cur->bc_mp->m_bmap_dmxr[level != 0];
        return xfs_bmdr_maxrecs(cur->bc_private.b.forksize, level == 0);
}

STATIC void
xfs_bmbt_init_key_from_rec(
        union xfs_btree_key     *key,
        union xfs_btree_rec     *rec)
{
        key->bmbt.br_startoff =
                cpu_to_be64(xfs_bmbt_disk_get_startoff(&rec->bmbt));
}

STATIC void
xfs_bmbt_init_high_key_from_rec(
        union xfs_btree_key     *key,
        union xfs_btree_rec     *rec)
{
        key->bmbt.br_startoff = cpu_to_be64(
                        xfs_bmbt_disk_get_startoff(&rec->bmbt) +
                        xfs_bmbt_disk_get_blockcount(&rec->bmbt) - 1);
}

STATIC void
xfs_bmbt_init_rec_from_cur(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *rec)
{
        xfs_bmbt_disk_set_all(&rec->bmbt, &cur->bc_rec.b);
}

STATIC void
xfs_bmbt_init_ptr_from_cur(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr)
{
        ptr->l = 0;
}

STATIC int64_t
xfs_bmbt_key_diff(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *key)
{
        return (int64_t)be64_to_cpu(key->bmbt.br_startoff) -
                                      cur->bc_rec.b.br_startoff;
}

STATIC int64_t
xfs_bmbt_diff_two_keys(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *k1,
        union xfs_btree_key     *k2)
{
        return (int64_t)be64_to_cpu(k1->bmbt.br_startoff) -
                          be64_to_cpu(k2->bmbt.br_startoff);
}

static xfs_failaddr_t
xfs_bmbt_verify(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        xfs_failaddr_t          fa;
        unsigned int            level;

        switch (block->bb_magic) {
        case cpu_to_be32(XFS_BMAP_CRC_MAGIC):
                /*
                 * XXX: need a better way of verifying the owner here. Right now
                 * just make sure there has been one set.
                 */
                fa = xfs_btree_lblock_v5hdr_verify(bp, XFS_RMAP_OWN_UNKNOWN);
                if (fa)
                        return fa;
                /* fall through */
        case cpu_to_be32(XFS_BMAP_MAGIC):
                break;
        default:
                return __this_address;
        }

        /*
         * numrecs and level verification.
         *
         * We don't know what fork we belong to, so just verify that the level
         * is less than the maximum of the two. Later checks will be more
         * precise.
         */
        level = be16_to_cpu(block->bb_level);
        if (level > max(mp->m_bm_maxlevels[0], mp->m_bm_maxlevels[1]))
                return __this_address;

        return xfs_btree_lblock_verify(bp, mp->m_bmap_dmxr[level != 0]);
}

static void
xfs_bmbt_read_verify(
        struct xfs_buf  *bp)
{
        xfs_failaddr_t  fa;

        if (!xfs_btree_lblock_verify_crc(bp))
                xfs_verifier_error(bp, -EFSBADCRC, __this_address);
        else {
                fa = xfs_bmbt_verify(bp);
                if (fa)
                        xfs_verifier_error(bp, -EFSCORRUPTED, fa);
        }

        if (bp->b_error)
                trace_xfs_btree_corrupt(bp, _RET_IP_);
}

static void
xfs_bmbt_write_verify(
        struct xfs_buf  *bp)
{
        xfs_failaddr_t  fa;

        fa = xfs_bmbt_verify(bp);
        if (fa) {
                trace_xfs_btree_corrupt(bp, _RET_IP_);
                xfs_verifier_error(bp, -EFSCORRUPTED, fa);
                return;
        }
        xfs_btree_lblock_calc_crc(bp);
}

const struct xfs_buf_ops xfs_bmbt_buf_ops = {
        .name = "xfs_bmbt",
        .verify_read = xfs_bmbt_read_verify,
        .verify_write = xfs_bmbt_write_verify,
        .verify_struct = xfs_bmbt_verify,
};


STATIC int
xfs_bmbt_keys_inorder(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *k1,
        union xfs_btree_key     *k2)
{
        return be64_to_cpu(k1->bmbt.br_startoff) <
                be64_to_cpu(k2->bmbt.br_startoff);
}

STATIC int
xfs_bmbt_recs_inorder(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *r1,
        union xfs_btree_rec     *r2)
{
        return xfs_bmbt_disk_get_startoff(&r1->bmbt) +
                xfs_bmbt_disk_get_blockcount(&r1->bmbt) <=
                xfs_bmbt_disk_get_startoff(&r2->bmbt);
}

static const struct xfs_btree_ops xfs_bmbt_ops = {
        .rec_len                = sizeof(xfs_bmbt_rec_t),
        .key_len                = sizeof(xfs_bmbt_key_t),

        .dup_cursor             = xfs_bmbt_dup_cursor,
        .update_cursor          = xfs_bmbt_update_cursor,
        .alloc_block            = xfs_bmbt_alloc_block,
        .free_block             = xfs_bmbt_free_block,
        .get_maxrecs            = xfs_bmbt_get_maxrecs,
        .get_minrecs            = xfs_bmbt_get_minrecs,
        .get_dmaxrecs           = xfs_bmbt_get_dmaxrecs,
        .init_key_from_rec      = xfs_bmbt_init_key_from_rec,
        .init_high_key_from_rec = xfs_bmbt_init_high_key_from_rec,
        .init_rec_from_cur      = xfs_bmbt_init_rec_from_cur,
        .init_ptr_from_cur      = xfs_bmbt_init_ptr_from_cur,
        .key_diff               = xfs_bmbt_key_diff,
        .diff_two_keys          = xfs_bmbt_diff_two_keys,
        .buf_ops                = &xfs_bmbt_buf_ops,
        .keys_inorder           = xfs_bmbt_keys_inorder,
        .recs_inorder           = xfs_bmbt_recs_inorder,
};

/*
 * Allocate a new bmap btree cursor.
 */
struct xfs_btree_cur *                          /* new bmap btree cursor */
xfs_bmbt_init_cursor(
        struct xfs_mount        *mp,            /* file system mount point */
        struct xfs_trans        *tp,            /* transaction pointer */
        struct xfs_inode        *ip,            /* inode owning the btree */
        int                     whichfork)      /* data or attr fork */
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_btree_cur    *cur;
        ASSERT(whichfork != XFS_COW_FORK);

        cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_NOFS);

        cur->bc_tp = tp;
        cur->bc_mp = mp;
        cur->bc_nlevels = be16_to_cpu(ifp->if_broot->bb_level) + 1;
        cur->bc_btnum = XFS_BTNUM_BMAP;
        cur->bc_blocklog = mp->m_sb.sb_blocklog;
        cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_bmbt_2);

        cur->bc_ops = &xfs_bmbt_ops;
        cur->bc_flags = XFS_BTREE_LONG_PTRS | XFS_BTREE_ROOT_IN_INODE;
        if (xfs_sb_version_hascrc(&mp->m_sb))
                cur->bc_flags |= XFS_BTREE_CRC_BLOCKS;

        cur->bc_private.b.forksize = XFS_IFORK_SIZE(ip, whichfork);
        cur->bc_private.b.ip = ip;
        cur->bc_private.b.firstblock = NULLFSBLOCK;
        cur->bc_private.b.dfops = NULL;
        cur->bc_private.b.allocated = 0;
        cur->bc_private.b.flags = 0;
        cur->bc_private.b.whichfork = whichfork;

        return cur;
}

/*
 * Calculate number of records in a bmap btree block.
 */
int
xfs_bmbt_maxrecs(
        struct xfs_mount        *mp,
        int                     blocklen,
        int                     leaf)
{
        blocklen -= XFS_BMBT_BLOCK_LEN(mp);

        if (leaf)
                return blocklen / sizeof(xfs_bmbt_rec_t);
        return blocklen / (sizeof(xfs_bmbt_key_t) + sizeof(xfs_bmbt_ptr_t));
}

/*
 * Calculate number of records in a bmap btree inode root.
 */
int
xfs_bmdr_maxrecs(
        int                     blocklen,
        int                     leaf)
{
        blocklen -= sizeof(xfs_bmdr_block_t);

        if (leaf)
                return blocklen / sizeof(xfs_bmdr_rec_t);
        return blocklen / (sizeof(xfs_bmdr_key_t) + sizeof(xfs_bmdr_ptr_t));
}

/*
 * Change the owner of a btree format fork fo the inode passed in. Change it to
 * the owner of that is passed in so that we can change owners before or after
 * we switch forks between inodes. The operation that the caller is doing will
 * determine whether is needs to change owner before or after the switch.
 *
 * For demand paged transactional modification, the fork switch should be done
 * after reading in all the blocks, modifying them and pinning them in the
 * transaction. For modification when the buffers are already pinned in memory,
 * the fork switch can be done before changing the owner as we won't need to
 * validate the owner until the btree buffers are unpinned and writes can occur
 * again.
 *
 * For recovery based ownership change, there is no transactional context and
 * so a buffer list must be supplied so that we can record the buffers that we
 * modified for the caller to issue IO on.
 */
int
xfs_bmbt_change_owner(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_ino_t               new_owner,
        struct list_head        *buffer_list)
{
        struct xfs_btree_cur    *cur;
        int                     error;

        ASSERT(tp || buffer_list);
        ASSERT(!(tp && buffer_list));
        if (whichfork == XFS_DATA_FORK)
                ASSERT(ip->i_d.di_format == XFS_DINODE_FMT_BTREE);
        else
                ASSERT(ip->i_d.di_aformat == XFS_DINODE_FMT_BTREE);

        cur = xfs_bmbt_init_cursor(ip->i_mount, tp, ip, whichfork);
        if (!cur)
                return -ENOMEM;
        cur->bc_private.b.flags |= XFS_BTCUR_BPRV_INVALID_OWNER;

        error = xfs_btree_change_owner(cur, new_owner, buffer_list);
        xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
        return error;
}