Merge tag 'xfs-for-linus-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / fs / xfs / libxfs / xfs_btree.c

/*
 * Copyright (c) 2000-2002,2005 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 "xfs.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_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_buf_item.h"
#include "xfs_btree.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_cksum.h"
#include "xfs_alloc.h"
#include "xfs_log.h"

/*
 * Cursor allocation zone.
 */
kmem_zone_t     *xfs_btree_cur_zone;

/*
 * Btree magic numbers.
 */
static const __uint32_t xfs_magics[2][XFS_BTNUM_MAX] = {
        { XFS_ABTB_MAGIC, XFS_ABTC_MAGIC, XFS_BMAP_MAGIC, XFS_IBT_MAGIC,
          XFS_FIBT_MAGIC },
        { XFS_ABTB_CRC_MAGIC, XFS_ABTC_CRC_MAGIC,
          XFS_BMAP_CRC_MAGIC, XFS_IBT_CRC_MAGIC, XFS_FIBT_CRC_MAGIC }
};
#define xfs_btree_magic(cur) \
        xfs_magics[!!((cur)->bc_flags & XFS_BTREE_CRC_BLOCKS)][cur->bc_btnum]


STATIC int                              /* error (0 or EFSCORRUPTED) */
xfs_btree_check_lblock(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_btree_block  *block, /* btree long form block pointer */
        int                     level,  /* level of the btree block */
        struct xfs_buf          *bp)    /* buffer for block, if any */
{
        int                     lblock_ok = 1; /* block passes checks */
        struct xfs_mount        *mp;    /* file system mount point */

        mp = cur->bc_mp;

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                lblock_ok = lblock_ok &&
                        uuid_equal(&block->bb_u.l.bb_uuid,
                                   &mp->m_sb.sb_meta_uuid) &&
                        block->bb_u.l.bb_blkno == cpu_to_be64(
                                bp ? bp->b_bn : XFS_BUF_DADDR_NULL);
        }

        lblock_ok = lblock_ok &&
                be32_to_cpu(block->bb_magic) == xfs_btree_magic(cur) &&
                be16_to_cpu(block->bb_level) == level &&
                be16_to_cpu(block->bb_numrecs) <=
                        cur->bc_ops->get_maxrecs(cur, level) &&
                block->bb_u.l.bb_leftsib &&
                (block->bb_u.l.bb_leftsib == cpu_to_be64(NULLFSBLOCK) ||
                 XFS_FSB_SANITY_CHECK(mp,
                        be64_to_cpu(block->bb_u.l.bb_leftsib))) &&
                block->bb_u.l.bb_rightsib &&
                (block->bb_u.l.bb_rightsib == cpu_to_be64(NULLFSBLOCK) ||
                 XFS_FSB_SANITY_CHECK(mp,
                        be64_to_cpu(block->bb_u.l.bb_rightsib)));

        if (unlikely(XFS_TEST_ERROR(!lblock_ok, mp,
                        XFS_ERRTAG_BTREE_CHECK_LBLOCK,
                        XFS_RANDOM_BTREE_CHECK_LBLOCK))) {
                if (bp)
                        trace_xfs_btree_corrupt(bp, _RET_IP_);
                XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }
        return 0;
}

STATIC int                              /* error (0 or EFSCORRUPTED) */
xfs_btree_check_sblock(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_btree_block  *block, /* btree short form block pointer */
        int                     level,  /* level of the btree block */
        struct xfs_buf          *bp)    /* buffer containing block */
{
        struct xfs_mount        *mp;    /* file system mount point */
        struct xfs_buf          *agbp;  /* buffer for ag. freespace struct */
        struct xfs_agf          *agf;   /* ag. freespace structure */
        xfs_agblock_t           agflen; /* native ag. freespace length */
        int                     sblock_ok = 1; /* block passes checks */

        mp = cur->bc_mp;
        agbp = cur->bc_private.a.agbp;
        agf = XFS_BUF_TO_AGF(agbp);
        agflen = be32_to_cpu(agf->agf_length);

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                sblock_ok = sblock_ok &&
                        uuid_equal(&block->bb_u.s.bb_uuid,
                                   &mp->m_sb.sb_meta_uuid) &&
                        block->bb_u.s.bb_blkno == cpu_to_be64(
                                bp ? bp->b_bn : XFS_BUF_DADDR_NULL);
        }

        sblock_ok = sblock_ok &&
                be32_to_cpu(block->bb_magic) == xfs_btree_magic(cur) &&
                be16_to_cpu(block->bb_level) == level &&
                be16_to_cpu(block->bb_numrecs) <=
                        cur->bc_ops->get_maxrecs(cur, level) &&
                (block->bb_u.s.bb_leftsib == cpu_to_be32(NULLAGBLOCK) ||
                 be32_to_cpu(block->bb_u.s.bb_leftsib) < agflen) &&
                block->bb_u.s.bb_leftsib &&
                (block->bb_u.s.bb_rightsib == cpu_to_be32(NULLAGBLOCK) ||
                 be32_to_cpu(block->bb_u.s.bb_rightsib) < agflen) &&
                block->bb_u.s.bb_rightsib;

        if (unlikely(XFS_TEST_ERROR(!sblock_ok, mp,
                        XFS_ERRTAG_BTREE_CHECK_SBLOCK,
                        XFS_RANDOM_BTREE_CHECK_SBLOCK))) {
                if (bp)
                        trace_xfs_btree_corrupt(bp, _RET_IP_);
                XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
                return -EFSCORRUPTED;
        }
        return 0;
}

/*
 * Debug routine: check that block header is ok.
 */
int
xfs_btree_check_block(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_btree_block  *block, /* generic btree block pointer */
        int                     level,  /* level of the btree block */
        struct xfs_buf          *bp)    /* buffer containing block, if any */
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                return xfs_btree_check_lblock(cur, block, level, bp);
        else
                return xfs_btree_check_sblock(cur, block, level, bp);
}

/*
 * Check that (long) pointer is ok.
 */
int                                     /* error (0 or EFSCORRUPTED) */
xfs_btree_check_lptr(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_fsblock_t           bno,    /* btree block disk address */
        int                     level)  /* btree block level */
{
        XFS_WANT_CORRUPTED_RETURN(cur->bc_mp,
                level > 0 &&
                bno != NULLFSBLOCK &&
                XFS_FSB_SANITY_CHECK(cur->bc_mp, bno));
        return 0;
}

#ifdef DEBUG
/*
 * Check that (short) pointer is ok.
 */
STATIC int                              /* error (0 or EFSCORRUPTED) */
xfs_btree_check_sptr(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* btree block disk address */
        int                     level)  /* btree block level */
{
        xfs_agblock_t           agblocks = cur->bc_mp->m_sb.sb_agblocks;

        XFS_WANT_CORRUPTED_RETURN(cur->bc_mp,
                level > 0 &&
                bno != NULLAGBLOCK &&
                bno != 0 &&
                bno < agblocks);
        return 0;
}

/*
 * Check that block ptr is ok.
 */
STATIC int                              /* error (0 or EFSCORRUPTED) */
xfs_btree_check_ptr(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        union xfs_btree_ptr     *ptr,   /* btree block disk address */
        int                     index,  /* offset from ptr to check */
        int                     level)  /* btree block level */
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                return xfs_btree_check_lptr(cur,
                                be64_to_cpu((&ptr->l)[index]), level);
        } else {
                return xfs_btree_check_sptr(cur,
                                be32_to_cpu((&ptr->s)[index]), level);
        }
}
#endif

/*
 * Calculate CRC on the whole btree block and stuff it into the
 * long-form btree header.
 *
 * Prior to calculting the CRC, pull the LSN out of the buffer log item and put
 * it into the buffer so recovery knows what the last modification was that made
 * it to disk.
 */
void
xfs_btree_lblock_calc_crc(
        struct xfs_buf          *bp)
{
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_buf_log_item *bip = bp->b_fspriv;

        if (!xfs_sb_version_hascrc(&bp->b_target->bt_mount->m_sb))
                return;
        if (bip)
                block->bb_u.l.bb_lsn = cpu_to_be64(bip->bli_item.li_lsn);
        xfs_buf_update_cksum(bp, XFS_BTREE_LBLOCK_CRC_OFF);
}

bool
xfs_btree_lblock_verify_crc(
        struct xfs_buf          *bp)
{
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_mount        *mp = bp->b_target->bt_mount;

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                if (!xfs_log_check_lsn(mp, be64_to_cpu(block->bb_u.l.bb_lsn)))
                        return false;
                return xfs_buf_verify_cksum(bp, XFS_BTREE_LBLOCK_CRC_OFF);
        }

        return true;
}

/*
 * Calculate CRC on the whole btree block and stuff it into the
 * short-form btree header.
 *
 * Prior to calculting the CRC, pull the LSN out of the buffer log item and put
 * it into the buffer so recovery knows what the last modification was that made
 * it to disk.
 */
void
xfs_btree_sblock_calc_crc(
        struct xfs_buf          *bp)
{
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_buf_log_item *bip = bp->b_fspriv;

        if (!xfs_sb_version_hascrc(&bp->b_target->bt_mount->m_sb))
                return;
        if (bip)
                block->bb_u.s.bb_lsn = cpu_to_be64(bip->bli_item.li_lsn);
        xfs_buf_update_cksum(bp, XFS_BTREE_SBLOCK_CRC_OFF);
}

bool
xfs_btree_sblock_verify_crc(
        struct xfs_buf          *bp)
{
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_mount        *mp = bp->b_target->bt_mount;

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                if (!xfs_log_check_lsn(mp, be64_to_cpu(block->bb_u.s.bb_lsn)))
                        return false;
                return xfs_buf_verify_cksum(bp, XFS_BTREE_SBLOCK_CRC_OFF);
        }

        return true;
}

static int
xfs_btree_free_block(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp)
{
        int                     error;

        error = cur->bc_ops->free_block(cur, bp);
        if (!error) {
                xfs_trans_binval(cur->bc_tp, bp);
                XFS_BTREE_STATS_INC(cur, free);
        }
        return error;
}

/*
 * Delete the btree cursor.
 */
void
xfs_btree_del_cursor(
        xfs_btree_cur_t *cur,           /* btree cursor */
        int             error)          /* del because of error */
{
        int             i;              /* btree level */

        /*
         * Clear the buffer pointers, and release the buffers.
         * If we're doing this in the face of an error, we
         * need to make sure to inspect all of the entries
         * in the bc_bufs array for buffers to be unlocked.
         * This is because some of the btree code works from
         * level n down to 0, and if we get an error along
         * the way we won't have initialized all the entries
         * down to 0.
         */
        for (i = 0; i < cur->bc_nlevels; i++) {
                if (cur->bc_bufs[i])
                        xfs_trans_brelse(cur->bc_tp, cur->bc_bufs[i]);
                else if (!error)
                        break;
        }
        /*
         * Can't free a bmap cursor without having dealt with the
         * allocated indirect blocks' accounting.
         */
        ASSERT(cur->bc_btnum != XFS_BTNUM_BMAP ||
               cur->bc_private.b.allocated == 0);
        /*
         * Free the cursor.
         */
        kmem_zone_free(xfs_btree_cur_zone, cur);
}

/*
 * Duplicate the btree cursor.
 * Allocate a new one, copy the record, re-get the buffers.
 */
int                                     /* error */
xfs_btree_dup_cursor(
        xfs_btree_cur_t *cur,           /* input cursor */
        xfs_btree_cur_t **ncur)         /* output cursor */
{
        xfs_buf_t       *bp;            /* btree block's buffer pointer */
        int             error;          /* error return value */
        int             i;              /* level number of btree block */
        xfs_mount_t     *mp;            /* mount structure for filesystem */
        xfs_btree_cur_t *new;           /* new cursor value */
        xfs_trans_t     *tp;            /* transaction pointer, can be NULL */

        tp = cur->bc_tp;
        mp = cur->bc_mp;

        /*
         * Allocate a new cursor like the old one.
         */
        new = cur->bc_ops->dup_cursor(cur);

        /*
         * Copy the record currently in the cursor.
         */
        new->bc_rec = cur->bc_rec;

        /*
         * For each level current, re-get the buffer and copy the ptr value.
         */
        for (i = 0; i < new->bc_nlevels; i++) {
                new->bc_ptrs[i] = cur->bc_ptrs[i];
                new->bc_ra[i] = cur->bc_ra[i];
                bp = cur->bc_bufs[i];
                if (bp) {
                        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                                                   XFS_BUF_ADDR(bp), mp->m_bsize,
                                                   0, &bp,
                                                   cur->bc_ops->buf_ops);
                        if (error) {
                                xfs_btree_del_cursor(new, error);
                                *ncur = NULL;
                                return error;
                        }
                }
                new->bc_bufs[i] = bp;
        }
        *ncur = new;
        return 0;
}

/*
 * XFS btree block layout and addressing:
 *
 * There are two types of blocks in the btree: leaf and non-leaf blocks.
 *
 * The leaf record start with a header then followed by records containing
 * the values.  A non-leaf block also starts with the same header, and
 * then first contains lookup keys followed by an equal number of pointers
 * to the btree blocks at the previous level.
 *
 *              +--------+-------+-------+-------+-------+-------+-------+
 * Leaf:        | header | rec 1 | rec 2 | rec 3 | rec 4 | rec 5 | rec N |
 *              +--------+-------+-------+-------+-------+-------+-------+
 *
 *              +--------+-------+-------+-------+-------+-------+-------+
 * Non-Leaf:    | header | key 1 | key 2 | key N | ptr 1 | ptr 2 | ptr N |
 *              +--------+-------+-------+-------+-------+-------+-------+
 *
 * The header is called struct xfs_btree_block for reasons better left unknown
 * and comes in different versions for short (32bit) and long (64bit) block
 * pointers.  The record and key structures are defined by the btree instances
 * and opaque to the btree core.  The block pointers are simple disk endian
 * integers, available in a short (32bit) and long (64bit) variant.
 *
 * The helpers below calculate the offset of a given record, key or pointer
 * into a btree block (xfs_btree_*_offset) or return a pointer to the given
 * record, key or pointer (xfs_btree_*_addr).  Note that all addressing
 * inside the btree block is done using indices starting at one, not zero!
 */

/*
 * Return size of the btree block header for this btree instance.
 */
static inline size_t xfs_btree_block_len(struct xfs_btree_cur *cur)
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                if (cur->bc_flags & XFS_BTREE_CRC_BLOCKS)
                        return XFS_BTREE_LBLOCK_CRC_LEN;
                return XFS_BTREE_LBLOCK_LEN;
        }
        if (cur->bc_flags & XFS_BTREE_CRC_BLOCKS)
                return XFS_BTREE_SBLOCK_CRC_LEN;
        return XFS_BTREE_SBLOCK_LEN;
}

/*
 * Return size of btree block pointers for this btree instance.
 */
static inline size_t xfs_btree_ptr_len(struct xfs_btree_cur *cur)
{
        return (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?
                sizeof(__be64) : sizeof(__be32);
}

/*
 * Calculate offset of the n-th record in a btree block.
 */
STATIC size_t
xfs_btree_rec_offset(
        struct xfs_btree_cur    *cur,
        int                     n)
{
        return xfs_btree_block_len(cur) +
                (n - 1) * cur->bc_ops->rec_len;
}

/*
 * Calculate offset of the n-th key in a btree block.
 */
STATIC size_t
xfs_btree_key_offset(
        struct xfs_btree_cur    *cur,
        int                     n)
{
        return xfs_btree_block_len(cur) +
                (n - 1) * cur->bc_ops->key_len;
}

/*
 * Calculate offset of the n-th block pointer in a btree block.
 */
STATIC size_t
xfs_btree_ptr_offset(
        struct xfs_btree_cur    *cur,
        int                     n,
        int                     level)
{
        return xfs_btree_block_len(cur) +
                cur->bc_ops->get_maxrecs(cur, level) * cur->bc_ops->key_len +
                (n - 1) * xfs_btree_ptr_len(cur);
}

/*
 * Return a pointer to the n-th record in the btree block.
 */
STATIC union xfs_btree_rec *
xfs_btree_rec_addr(
        struct xfs_btree_cur    *cur,
        int                     n,
        struct xfs_btree_block  *block)
{
        return (union xfs_btree_rec *)
                ((char *)block + xfs_btree_rec_offset(cur, n));
}

/*
 * Return a pointer to the n-th key in the btree block.
 */
STATIC union xfs_btree_key *
xfs_btree_key_addr(
        struct xfs_btree_cur    *cur,
        int                     n,
        struct xfs_btree_block  *block)
{
        return (union xfs_btree_key *)
                ((char *)block + xfs_btree_key_offset(cur, n));
}

/*
 * Return a pointer to the n-th block pointer in the btree block.
 */
STATIC union xfs_btree_ptr *
xfs_btree_ptr_addr(
        struct xfs_btree_cur    *cur,
        int                     n,
        struct xfs_btree_block  *block)
{
        int                     level = xfs_btree_get_level(block);

        ASSERT(block->bb_level != 0);

        return (union xfs_btree_ptr *)
                ((char *)block + xfs_btree_ptr_offset(cur, n, level));
}

/*
 * Get the root block which is stored in the inode.
 *
 * For now this btree implementation assumes the btree root is always
 * stored in the if_broot field of an inode fork.
 */
STATIC struct xfs_btree_block *
xfs_btree_get_iroot(
        struct xfs_btree_cur    *cur)
{
        struct xfs_ifork        *ifp;

        ifp = XFS_IFORK_PTR(cur->bc_private.b.ip, cur->bc_private.b.whichfork);
        return (struct xfs_btree_block *)ifp->if_broot;
}

/*
 * Retrieve the block pointer from the cursor at the given level.
 * This may be an inode btree root or from a buffer.
 */
STATIC struct xfs_btree_block *         /* generic btree block pointer */
xfs_btree_get_block(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     level,  /* level in btree */
        struct xfs_buf          **bpp)  /* buffer containing the block */
{
        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            (level == cur->bc_nlevels - 1)) {
                *bpp = NULL;
                return xfs_btree_get_iroot(cur);
        }

        *bpp = cur->bc_bufs[level];
        return XFS_BUF_TO_BLOCK(*bpp);
}

/*
 * Get a buffer for the block, return it with no data read.
 * Long-form addressing.
 */
xfs_buf_t *                             /* buffer for fsbno */
xfs_btree_get_bufl(
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_fsblock_t   fsbno,          /* file system block number */
        uint            lock)           /* lock flags for get_buf */
{
        xfs_daddr_t             d;              /* real disk block address */

        ASSERT(fsbno != NULLFSBLOCK);
        d = XFS_FSB_TO_DADDR(mp, fsbno);
        return xfs_trans_get_buf(tp, mp->m_ddev_targp, d, mp->m_bsize, lock);
}

/*
 * Get a buffer for the block, return it with no data read.
 * Short-form addressing.
 */
xfs_buf_t *                             /* buffer for agno/agbno */
xfs_btree_get_bufs(
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_agnumber_t  agno,           /* allocation group number */
        xfs_agblock_t   agbno,          /* allocation group block number */
        uint            lock)           /* lock flags for get_buf */
{
        xfs_daddr_t             d;              /* real disk block address */

        ASSERT(agno != NULLAGNUMBER);
        ASSERT(agbno != NULLAGBLOCK);
        d = XFS_AGB_TO_DADDR(mp, agno, agbno);
        return xfs_trans_get_buf(tp, mp->m_ddev_targp, d, mp->m_bsize, lock);
}

/*
 * Check for the cursor referring to the last block at the given level.
 */
int                                     /* 1=is last block, 0=not last block */
xfs_btree_islastblock(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level)  /* level to check */
{
        struct xfs_btree_block  *block; /* generic btree block pointer */
        xfs_buf_t               *bp;    /* buffer containing block */

        block = xfs_btree_get_block(cur, level, &bp);
        xfs_btree_check_block(cur, block, level, bp);
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                return block->bb_u.l.bb_rightsib == cpu_to_be64(NULLFSBLOCK);
        else
                return block->bb_u.s.bb_rightsib == cpu_to_be32(NULLAGBLOCK);
}

/*
 * Change the cursor to point to the first record at the given level.
 * Other levels are unaffected.
 */
STATIC int                              /* success=1, failure=0 */
xfs_btree_firstrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level)  /* level to change */
{
        struct xfs_btree_block  *block; /* generic btree block pointer */
        xfs_buf_t               *bp;    /* buffer containing block */

        /*
         * Get the block pointer for this level.
         */
        block = xfs_btree_get_block(cur, level, &bp);
        xfs_btree_check_block(cur, block, level, bp);
        /*
         * It's empty, there is no such record.
         */
        if (!block->bb_numrecs)
                return 0;
        /*
         * Set the ptr value to 1, that's the first record/key.
         */
        cur->bc_ptrs[level] = 1;
        return 1;
}

/*
 * Change the cursor to point to the last record in the current block
 * at the given level.  Other levels are unaffected.
 */
STATIC int                              /* success=1, failure=0 */
xfs_btree_lastrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level)  /* level to change */
{
        struct xfs_btree_block  *block; /* generic btree block pointer */
        xfs_buf_t               *bp;    /* buffer containing block */

        /*
         * Get the block pointer for this level.
         */
        block = xfs_btree_get_block(cur, level, &bp);
        xfs_btree_check_block(cur, block, level, bp);
        /*
         * It's empty, there is no such record.
         */
        if (!block->bb_numrecs)
                return 0;
        /*
         * Set the ptr value to numrecs, that's the last record/key.
         */
        cur->bc_ptrs[level] = be16_to_cpu(block->bb_numrecs);
        return 1;
}

/*
 * Compute first and last byte offsets for the fields given.
 * Interprets the offsets table, which contains struct field offsets.
 */
void
xfs_btree_offsets(
        __int64_t       fields,         /* bitmask of fields */
        const short     *offsets,       /* table of field offsets */
        int             nbits,          /* number of bits to inspect */
        int             *first,         /* output: first byte offset */
        int             *last)          /* output: last byte offset */
{
        int             i;              /* current bit number */
        __int64_t       imask;          /* mask for current bit number */

        ASSERT(fields != 0);
        /*
         * Find the lowest bit, so the first byte offset.
         */
        for (i = 0, imask = 1LL; ; i++, imask <<= 1) {
                if (imask & fields) {
                        *first = offsets[i];
                        break;
                }
        }
        /*
         * Find the highest bit, so the last byte offset.
         */
        for (i = nbits - 1, imask = 1LL << i; ; i--, imask >>= 1) {
                if (imask & fields) {
                        *last = offsets[i + 1] - 1;
                        break;
                }
        }
}

/*
 * Get a buffer for the block, return it read in.
 * Long-form addressing.
 */
int
xfs_btree_read_bufl(
        struct xfs_mount        *mp,            /* file system mount point */
        struct xfs_trans        *tp,            /* transaction pointer */
        xfs_fsblock_t           fsbno,          /* file system block number */
        uint                    lock,           /* lock flags for read_buf */
        struct xfs_buf          **bpp,          /* buffer for fsbno */
        int                     refval,         /* ref count value for buffer */
        const struct xfs_buf_ops *ops)
{
        struct xfs_buf          *bp;            /* return value */
        xfs_daddr_t             d;              /* real disk block address */
        int                     error;

        ASSERT(fsbno != NULLFSBLOCK);
        d = XFS_FSB_TO_DADDR(mp, fsbno);
        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
                                   mp->m_bsize, lock, &bp, ops);
        if (error)
                return error;
        if (bp)
                xfs_buf_set_ref(bp, refval);
        *bpp = bp;
        return 0;
}

/*
 * Read-ahead the block, don't wait for it, don't return a buffer.
 * Long-form addressing.
 */
/* ARGSUSED */
void
xfs_btree_reada_bufl(
        struct xfs_mount        *mp,            /* file system mount point */
        xfs_fsblock_t           fsbno,          /* file system block number */
        xfs_extlen_t            count,          /* count of filesystem blocks */
        const struct xfs_buf_ops *ops)
{
        xfs_daddr_t             d;

        ASSERT(fsbno != NULLFSBLOCK);
        d = XFS_FSB_TO_DADDR(mp, fsbno);
        xfs_buf_readahead(mp->m_ddev_targp, d, mp->m_bsize * count, ops);
}

/*
 * Read-ahead the block, don't wait for it, don't return a buffer.
 * Short-form addressing.
 */
/* ARGSUSED */
void
xfs_btree_reada_bufs(
        struct xfs_mount        *mp,            /* file system mount point */
        xfs_agnumber_t          agno,           /* allocation group number */
        xfs_agblock_t           agbno,          /* allocation group block number */
        xfs_extlen_t            count,          /* count of filesystem blocks */
        const struct xfs_buf_ops *ops)
{
        xfs_daddr_t             d;

        ASSERT(agno != NULLAGNUMBER);
        ASSERT(agbno != NULLAGBLOCK);
        d = XFS_AGB_TO_DADDR(mp, agno, agbno);
        xfs_buf_readahead(mp->m_ddev_targp, d, mp->m_bsize * count, ops);
}

STATIC int
xfs_btree_readahead_lblock(
        struct xfs_btree_cur    *cur,
        int                     lr,
        struct xfs_btree_block  *block)
{
        int                     rval = 0;
        xfs_fsblock_t           left = be64_to_cpu(block->bb_u.l.bb_leftsib);
        xfs_fsblock_t           right = be64_to_cpu(block->bb_u.l.bb_rightsib);

        if ((lr & XFS_BTCUR_LEFTRA) && left != NULLFSBLOCK) {
                xfs_btree_reada_bufl(cur->bc_mp, left, 1,
                                     cur->bc_ops->buf_ops);
                rval++;
        }

        if ((lr & XFS_BTCUR_RIGHTRA) && right != NULLFSBLOCK) {
                xfs_btree_reada_bufl(cur->bc_mp, right, 1,
                                     cur->bc_ops->buf_ops);
                rval++;
        }

        return rval;
}

STATIC int
xfs_btree_readahead_sblock(
        struct xfs_btree_cur    *cur,
        int                     lr,
        struct xfs_btree_block *block)
{
        int                     rval = 0;
        xfs_agblock_t           left = be32_to_cpu(block->bb_u.s.bb_leftsib);
        xfs_agblock_t           right = be32_to_cpu(block->bb_u.s.bb_rightsib);


        if ((lr & XFS_BTCUR_LEFTRA) && left != NULLAGBLOCK) {
                xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
                                     left, 1, cur->bc_ops->buf_ops);
                rval++;
        }

        if ((lr & XFS_BTCUR_RIGHTRA) && right != NULLAGBLOCK) {
                xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
                                     right, 1, cur->bc_ops->buf_ops);
                rval++;
        }

        return rval;
}

/*
 * Read-ahead btree blocks, at the given level.
 * Bits in lr are set from XFS_BTCUR_{LEFT,RIGHT}RA.
 */
STATIC int
xfs_btree_readahead(
        struct xfs_btree_cur    *cur,           /* btree cursor */
        int                     lev,            /* level in btree */
        int                     lr)             /* left/right bits */
{
        struct xfs_btree_block  *block;

        /*
         * No readahead needed if we are at the root level and the
         * btree root is stored in the inode.
         */
        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            (lev == cur->bc_nlevels - 1))
                return 0;

        if ((cur->bc_ra[lev] | lr) == cur->bc_ra[lev])
                return 0;

        cur->bc_ra[lev] |= lr;
        block = XFS_BUF_TO_BLOCK(cur->bc_bufs[lev]);

        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                return xfs_btree_readahead_lblock(cur, lr, block);
        return xfs_btree_readahead_sblock(cur, lr, block);
}

STATIC xfs_daddr_t
xfs_btree_ptr_to_daddr(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr)
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                ASSERT(ptr->l != cpu_to_be64(NULLFSBLOCK));

                return XFS_FSB_TO_DADDR(cur->bc_mp, be64_to_cpu(ptr->l));
        } else {
                ASSERT(cur->bc_private.a.agno != NULLAGNUMBER);
                ASSERT(ptr->s != cpu_to_be32(NULLAGBLOCK));

                return XFS_AGB_TO_DADDR(cur->bc_mp, cur->bc_private.a.agno,
                                        be32_to_cpu(ptr->s));
        }
}

/*
 * Readahead @count btree blocks at the given @ptr location.
 *
 * We don't need to care about long or short form btrees here as we have a
 * method of converting the ptr directly to a daddr available to us.
 */
STATIC void
xfs_btree_readahead_ptr(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr,
        xfs_extlen_t            count)
{
        xfs_buf_readahead(cur->bc_mp->m_ddev_targp,
                          xfs_btree_ptr_to_daddr(cur, ptr),
                          cur->bc_mp->m_bsize * count, cur->bc_ops->buf_ops);
}

/*
 * Set the buffer for level "lev" in the cursor to bp, releasing
 * any previous buffer.
 */
STATIC void
xfs_btree_setbuf(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     lev,    /* level in btree */
        xfs_buf_t               *bp)    /* new buffer to set */
{
        struct xfs_btree_block  *b;     /* btree block */

        if (cur->bc_bufs[lev])
                xfs_trans_brelse(cur->bc_tp, cur->bc_bufs[lev]);
        cur->bc_bufs[lev] = bp;
        cur->bc_ra[lev] = 0;

        b = XFS_BUF_TO_BLOCK(bp);
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                if (b->bb_u.l.bb_leftsib == cpu_to_be64(NULLFSBLOCK))
                        cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
                if (b->bb_u.l.bb_rightsib == cpu_to_be64(NULLFSBLOCK))
                        cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
        } else {
                if (b->bb_u.s.bb_leftsib == cpu_to_be32(NULLAGBLOCK))
                        cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
                if (b->bb_u.s.bb_rightsib == cpu_to_be32(NULLAGBLOCK))
                        cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
        }
}

STATIC int
xfs_btree_ptr_is_null(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr)
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                return ptr->l == cpu_to_be64(NULLFSBLOCK);
        else
                return ptr->s == cpu_to_be32(NULLAGBLOCK);
}

STATIC void
xfs_btree_set_ptr_null(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr)
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                ptr->l = cpu_to_be64(NULLFSBLOCK);
        else
                ptr->s = cpu_to_be32(NULLAGBLOCK);
}

/*
 * Get/set/init sibling pointers
 */
STATIC void
xfs_btree_get_sibling(
        struct xfs_btree_cur    *cur,
        struct xfs_btree_block  *block,
        union xfs_btree_ptr     *ptr,
        int                     lr)
{
        ASSERT(lr == XFS_BB_LEFTSIB || lr == XFS_BB_RIGHTSIB);

        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                if (lr == XFS_BB_RIGHTSIB)
                        ptr->l = block->bb_u.l.bb_rightsib;
                else
                        ptr->l = block->bb_u.l.bb_leftsib;
        } else {
                if (lr == XFS_BB_RIGHTSIB)
                        ptr->s = block->bb_u.s.bb_rightsib;
                else
                        ptr->s = block->bb_u.s.bb_leftsib;
        }
}

STATIC void
xfs_btree_set_sibling(
        struct xfs_btree_cur    *cur,
        struct xfs_btree_block  *block,
        union xfs_btree_ptr     *ptr,
        int                     lr)
{
        ASSERT(lr == XFS_BB_LEFTSIB || lr == XFS_BB_RIGHTSIB);

        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                if (lr == XFS_BB_RIGHTSIB)
                        block->bb_u.l.bb_rightsib = ptr->l;
                else
                        block->bb_u.l.bb_leftsib = ptr->l;
        } else {
                if (lr == XFS_BB_RIGHTSIB)
                        block->bb_u.s.bb_rightsib = ptr->s;
                else
                        block->bb_u.s.bb_leftsib = ptr->s;
        }
}

void
xfs_btree_init_block_int(
        struct xfs_mount        *mp,
        struct xfs_btree_block  *buf,
        xfs_daddr_t             blkno,
        __u32                   magic,
        __u16                   level,
        __u16                   numrecs,
        __u64                   owner,
        unsigned int            flags)
{
        buf->bb_magic = cpu_to_be32(magic);
        buf->bb_level = cpu_to_be16(level);
        buf->bb_numrecs = cpu_to_be16(numrecs);

        if (flags & XFS_BTREE_LONG_PTRS) {
                buf->bb_u.l.bb_leftsib = cpu_to_be64(NULLFSBLOCK);
                buf->bb_u.l.bb_rightsib = cpu_to_be64(NULLFSBLOCK);
                if (flags & XFS_BTREE_CRC_BLOCKS) {
                        buf->bb_u.l.bb_blkno = cpu_to_be64(blkno);
                        buf->bb_u.l.bb_owner = cpu_to_be64(owner);
                        uuid_copy(&buf->bb_u.l.bb_uuid, &mp->m_sb.sb_meta_uuid);
                        buf->bb_u.l.bb_pad = 0;
                        buf->bb_u.l.bb_lsn = 0;
                }
        } else {
                /* owner is a 32 bit value on short blocks */
                __u32 __owner = (__u32)owner;

                buf->bb_u.s.bb_leftsib = cpu_to_be32(NULLAGBLOCK);
                buf->bb_u.s.bb_rightsib = cpu_to_be32(NULLAGBLOCK);
                if (flags & XFS_BTREE_CRC_BLOCKS) {
                        buf->bb_u.s.bb_blkno = cpu_to_be64(blkno);
                        buf->bb_u.s.bb_owner = cpu_to_be32(__owner);
                        uuid_copy(&buf->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid);
                        buf->bb_u.s.bb_lsn = 0;
                }
        }
}

void
xfs_btree_init_block(
        struct xfs_mount *mp,
        struct xfs_buf  *bp,
        __u32           magic,
        __u16           level,
        __u16           numrecs,
        __u64           owner,
        unsigned int    flags)
{
        xfs_btree_init_block_int(mp, XFS_BUF_TO_BLOCK(bp), bp->b_bn,
                                 magic, level, numrecs, owner, flags);
}

STATIC void
xfs_btree_init_block_cur(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp,
        int                     level,
        int                     numrecs)
{
        __u64 owner;

        /*
         * we can pull the owner from the cursor right now as the different
         * owners align directly with the pointer size of the btree. This may
         * change in future, but is safe for current users of the generic btree
         * code.
         */
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                owner = cur->bc_private.b.ip->i_ino;
        else
                owner = cur->bc_private.a.agno;

        xfs_btree_init_block_int(cur->bc_mp, XFS_BUF_TO_BLOCK(bp), bp->b_bn,
                                 xfs_btree_magic(cur), level, numrecs,
                                 owner, cur->bc_flags);
}

/*
 * Return true if ptr is the last record in the btree and
 * we need to track updates to this record.  The decision
 * will be further refined in the update_lastrec method.
 */
STATIC int
xfs_btree_is_lastrec(
        struct xfs_btree_cur    *cur,
        struct xfs_btree_block  *block,
        int                     level)
{
        union xfs_btree_ptr     ptr;

        if (level > 0)
                return 0;
        if (!(cur->bc_flags & XFS_BTREE_LASTREC_UPDATE))
                return 0;

        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
        if (!xfs_btree_ptr_is_null(cur, &ptr))
                return 0;
        return 1;
}

STATIC void
xfs_btree_buf_to_ptr(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp,
        union xfs_btree_ptr     *ptr)
{
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                ptr->l = cpu_to_be64(XFS_DADDR_TO_FSB(cur->bc_mp,
                                        XFS_BUF_ADDR(bp)));
        else {
                ptr->s = cpu_to_be32(xfs_daddr_to_agbno(cur->bc_mp,
                                        XFS_BUF_ADDR(bp)));
        }
}

STATIC void
xfs_btree_set_refs(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp)
{
        switch (cur->bc_btnum) {
        case XFS_BTNUM_BNO:
        case XFS_BTNUM_CNT:
                xfs_buf_set_ref(bp, XFS_ALLOC_BTREE_REF);
                break;
        case XFS_BTNUM_INO:
        case XFS_BTNUM_FINO:
                xfs_buf_set_ref(bp, XFS_INO_BTREE_REF);
                break;
        case XFS_BTNUM_BMAP:
                xfs_buf_set_ref(bp, XFS_BMAP_BTREE_REF);
                break;
        default:
                ASSERT(0);
        }
}

STATIC int
xfs_btree_get_buf_block(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr,
        int                     flags,
        struct xfs_btree_block  **block,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = cur->bc_mp;
        xfs_daddr_t             d;

        /* need to sort out how callers deal with failures first */
        ASSERT(!(flags & XBF_TRYLOCK));

        d = xfs_btree_ptr_to_daddr(cur, ptr);
        *bpp = xfs_trans_get_buf(cur->bc_tp, mp->m_ddev_targp, d,
                                 mp->m_bsize, flags);

        if (!*bpp)
                return -ENOMEM;

        (*bpp)->b_ops = cur->bc_ops->buf_ops;
        *block = XFS_BUF_TO_BLOCK(*bpp);
        return 0;
}

/*
 * Read in the buffer at the given ptr and return the buffer and
 * the block pointer within the buffer.
 */
STATIC int
xfs_btree_read_buf_block(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr,
        int                     flags,
        struct xfs_btree_block  **block,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = cur->bc_mp;
        xfs_daddr_t             d;
        int                     error;

        /* need to sort out how callers deal with failures first */
        ASSERT(!(flags & XBF_TRYLOCK));

        d = xfs_btree_ptr_to_daddr(cur, ptr);
        error = xfs_trans_read_buf(mp, cur->bc_tp, mp->m_ddev_targp, d,
                                   mp->m_bsize, flags, bpp,
                                   cur->bc_ops->buf_ops);
        if (error)
                return error;

        xfs_btree_set_refs(cur, *bpp);
        *block = XFS_BUF_TO_BLOCK(*bpp);
        return 0;
}

/*
 * Copy keys from one btree block to another.
 */
STATIC void
xfs_btree_copy_keys(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *dst_key,
        union xfs_btree_key     *src_key,
        int                     numkeys)
{
        ASSERT(numkeys >= 0);
        memcpy(dst_key, src_key, numkeys * cur->bc_ops->key_len);
}

/*
 * Copy records from one btree block to another.
 */
STATIC void
xfs_btree_copy_recs(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *dst_rec,
        union xfs_btree_rec     *src_rec,
        int                     numrecs)
{
        ASSERT(numrecs >= 0);
        memcpy(dst_rec, src_rec, numrecs * cur->bc_ops->rec_len);
}

/*
 * Copy block pointers from one btree block to another.
 */
STATIC void
xfs_btree_copy_ptrs(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *dst_ptr,
        union xfs_btree_ptr     *src_ptr,
        int                     numptrs)
{
        ASSERT(numptrs >= 0);
        memcpy(dst_ptr, src_ptr, numptrs * xfs_btree_ptr_len(cur));
}

/*
 * Shift keys one index left/right inside a single btree block.
 */
STATIC void
xfs_btree_shift_keys(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *key,
        int                     dir,
        int                     numkeys)
{
        char                    *dst_key;

        ASSERT(numkeys >= 0);
        ASSERT(dir == 1 || dir == -1);

        dst_key = (char *)key + (dir * cur->bc_ops->key_len);
        memmove(dst_key, key, numkeys * cur->bc_ops->key_len);
}

/*
 * Shift records one index left/right inside a single btree block.
 */
STATIC void
xfs_btree_shift_recs(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *rec,
        int                     dir,
        int                     numrecs)
{
        char                    *dst_rec;

        ASSERT(numrecs >= 0);
        ASSERT(dir == 1 || dir == -1);

        dst_rec = (char *)rec + (dir * cur->bc_ops->rec_len);
        memmove(dst_rec, rec, numrecs * cur->bc_ops->rec_len);
}

/*
 * Shift block pointers one index left/right inside a single btree block.
 */
STATIC void
xfs_btree_shift_ptrs(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr,
        int                     dir,
        int                     numptrs)
{
        char                    *dst_ptr;

        ASSERT(numptrs >= 0);
        ASSERT(dir == 1 || dir == -1);

        dst_ptr = (char *)ptr + (dir * xfs_btree_ptr_len(cur));
        memmove(dst_ptr, ptr, numptrs * xfs_btree_ptr_len(cur));
}

/*
 * Log key values from the btree block.
 */
STATIC void
xfs_btree_log_keys(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp,
        int                     first,
        int                     last)
{
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGBII(cur, bp, first, last);

        if (bp) {
                xfs_trans_buf_set_type(cur->bc_tp, bp, XFS_BLFT_BTREE_BUF);
                xfs_trans_log_buf(cur->bc_tp, bp,
                                  xfs_btree_key_offset(cur, first),
                                  xfs_btree_key_offset(cur, last + 1) - 1);
        } else {
                xfs_trans_log_inode(cur->bc_tp, cur->bc_private.b.ip,
                                xfs_ilog_fbroot(cur->bc_private.b.whichfork));
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
}

/*
 * Log record values from the btree block.
 */
void
xfs_btree_log_recs(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp,
        int                     first,
        int                     last)
{
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGBII(cur, bp, first, last);

        xfs_trans_buf_set_type(cur->bc_tp, bp, XFS_BLFT_BTREE_BUF);
        xfs_trans_log_buf(cur->bc_tp, bp,
                          xfs_btree_rec_offset(cur, first),
                          xfs_btree_rec_offset(cur, last + 1) - 1);

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
}

/*
 * Log block pointer fields from a btree block (nonleaf).
 */
STATIC void
xfs_btree_log_ptrs(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_buf          *bp,    /* buffer containing btree block */
        int                     first,  /* index of first pointer to log */
        int                     last)   /* index of last pointer to log */
{
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGBII(cur, bp, first, last);

        if (bp) {
                struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
                int                     level = xfs_btree_get_level(block);

                xfs_trans_buf_set_type(cur->bc_tp, bp, XFS_BLFT_BTREE_BUF);
                xfs_trans_log_buf(cur->bc_tp, bp,
                                xfs_btree_ptr_offset(cur, first, level),
                                xfs_btree_ptr_offset(cur, last + 1, level) - 1);
        } else {
                xfs_trans_log_inode(cur->bc_tp, cur->bc_private.b.ip,
                        xfs_ilog_fbroot(cur->bc_private.b.whichfork));
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
}

/*
 * Log fields from a btree block header.
 */
void
xfs_btree_log_block(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_buf          *bp,    /* buffer containing btree block */
        int                     fields) /* mask of fields: XFS_BB_... */
{
        int                     first;  /* first byte offset logged */
        int                     last;   /* last byte offset logged */
        static const short      soffsets[] = {  /* table of offsets (short) */
                offsetof(struct xfs_btree_block, bb_magic),
                offsetof(struct xfs_btree_block, bb_level),
                offsetof(struct xfs_btree_block, bb_numrecs),
                offsetof(struct xfs_btree_block, bb_u.s.bb_leftsib),
                offsetof(struct xfs_btree_block, bb_u.s.bb_rightsib),
                offsetof(struct xfs_btree_block, bb_u.s.bb_blkno),
                offsetof(struct xfs_btree_block, bb_u.s.bb_lsn),
                offsetof(struct xfs_btree_block, bb_u.s.bb_uuid),
                offsetof(struct xfs_btree_block, bb_u.s.bb_owner),
                offsetof(struct xfs_btree_block, bb_u.s.bb_crc),
                XFS_BTREE_SBLOCK_CRC_LEN
        };
        static const short      loffsets[] = {  /* table of offsets (long) */
                offsetof(struct xfs_btree_block, bb_magic),
                offsetof(struct xfs_btree_block, bb_level),
                offsetof(struct xfs_btree_block, bb_numrecs),
                offsetof(struct xfs_btree_block, bb_u.l.bb_leftsib),
                offsetof(struct xfs_btree_block, bb_u.l.bb_rightsib),
                offsetof(struct xfs_btree_block, bb_u.l.bb_blkno),
                offsetof(struct xfs_btree_block, bb_u.l.bb_lsn),
                offsetof(struct xfs_btree_block, bb_u.l.bb_uuid),
                offsetof(struct xfs_btree_block, bb_u.l.bb_owner),
                offsetof(struct xfs_btree_block, bb_u.l.bb_crc),
                offsetof(struct xfs_btree_block, bb_u.l.bb_pad),
                XFS_BTREE_LBLOCK_CRC_LEN
        };

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGBI(cur, bp, fields);

        if (bp) {
                int nbits;

                if (cur->bc_flags & XFS_BTREE_CRC_BLOCKS) {
                        /*
                         * We don't log the CRC when updating a btree
                         * block but instead recreate it during log
                         * recovery.  As the log buffers have checksums
                         * of their own this is safe and avoids logging a crc
                         * update in a lot of places.
                         */
                        if (fields == XFS_BB_ALL_BITS)
                                fields = XFS_BB_ALL_BITS_CRC;
                        nbits = XFS_BB_NUM_BITS_CRC;
                } else {
                        nbits = XFS_BB_NUM_BITS;
                }
                xfs_btree_offsets(fields,
                                  (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?
                                        loffsets : soffsets,
                                  nbits, &first, &last);
                xfs_trans_buf_set_type(cur->bc_tp, bp, XFS_BLFT_BTREE_BUF);
                xfs_trans_log_buf(cur->bc_tp, bp, first, last);
        } else {
                xfs_trans_log_inode(cur->bc_tp, cur->bc_private.b.ip,
                        xfs_ilog_fbroot(cur->bc_private.b.whichfork));
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
}

/*
 * Increment cursor by one record at the level.
 * For nonzero levels the leaf-ward information is untouched.
 */
int                                             /* error */
xfs_btree_increment(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     *stat)          /* success/failure */
{
        struct xfs_btree_block  *block;
        union xfs_btree_ptr     ptr;
        struct xfs_buf          *bp;
        int                     error;          /* error return value */
        int                     lev;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, level);

        ASSERT(level < cur->bc_nlevels);

        /* Read-ahead to the right at this level. */
        xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);

        /* Get a pointer to the btree block. */
        block = xfs_btree_get_block(cur, level, &bp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, level, bp);
        if (error)
                goto error0;
#endif

        /* We're done if we remain in the block after the increment. */
        if (++cur->bc_ptrs[level] <= xfs_btree_get_numrecs(block))
                goto out1;

        /* Fail if we just went off the right edge of the tree. */
        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
        if (xfs_btree_ptr_is_null(cur, &ptr))
                goto out0;

        XFS_BTREE_STATS_INC(cur, increment);

        /*
         * March up the tree incrementing pointers.
         * Stop when we don't go off the right edge of a block.
         */
        for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
                block = xfs_btree_get_block(cur, lev, &bp);

#ifdef DEBUG
                error = xfs_btree_check_block(cur, block, lev, bp);
                if (error)
                        goto error0;
#endif

                if (++cur->bc_ptrs[lev] <= xfs_btree_get_numrecs(block))
                        break;

                /* Read-ahead the right block for the next loop. */
                xfs_btree_readahead(cur, lev, XFS_BTCUR_RIGHTRA);
        }

        /*
         * If we went off the root then we are either seriously
         * confused or have the tree root in an inode.
         */
        if (lev == cur->bc_nlevels) {
                if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
                        goto out0;
                ASSERT(0);
                error = -EFSCORRUPTED;
                goto error0;
        }
        ASSERT(lev < cur->bc_nlevels);

        /*
         * Now walk back down the tree, fixing up the cursor's buffer
         * pointers and key numbers.
         */
        for (block = xfs_btree_get_block(cur, lev, &bp); lev > level; ) {
                union xfs_btree_ptr     *ptrp;

                ptrp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[lev], block);
                --lev;
                error = xfs_btree_read_buf_block(cur, ptrp, 0, &block, &bp);
                if (error)
                        goto error0;

                xfs_btree_setbuf(cur, lev, bp);
                cur->bc_ptrs[lev] = 1;
        }
out1:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;

out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Decrement cursor by one record at the level.
 * For nonzero levels the leaf-ward information is untouched.
 */
int                                             /* error */
xfs_btree_decrement(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     *stat)          /* success/failure */
{
        struct xfs_btree_block  *block;
        xfs_buf_t               *bp;
        int                     error;          /* error return value */
        int                     lev;
        union xfs_btree_ptr     ptr;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, level);

        ASSERT(level < cur->bc_nlevels);

        /* Read-ahead to the left at this level. */
        xfs_btree_readahead(cur, level, XFS_BTCUR_LEFTRA);

        /* We're done if we remain in the block after the decrement. */
        if (--cur->bc_ptrs[level] > 0)
                goto out1;

        /* Get a pointer to the btree block. */
        block = xfs_btree_get_block(cur, level, &bp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, level, bp);
        if (error)
                goto error0;
#endif

        /* Fail if we just went off the left edge of the tree. */
        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_LEFTSIB);
        if (xfs_btree_ptr_is_null(cur, &ptr))
                goto out0;

        XFS_BTREE_STATS_INC(cur, decrement);

        /*
         * March up the tree decrementing pointers.
         * Stop when we don't go off the left edge of a block.
         */
        for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
                if (--cur->bc_ptrs[lev] > 0)
                        break;
                /* Read-ahead the left block for the next loop. */
                xfs_btree_readahead(cur, lev, XFS_BTCUR_LEFTRA);
        }

        /*
         * If we went off the root then we are seriously confused.
         * or the root of the tree is in an inode.
         */
        if (lev == cur->bc_nlevels) {
                if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
                        goto out0;
                ASSERT(0);
                error = -EFSCORRUPTED;
                goto error0;
        }
        ASSERT(lev < cur->bc_nlevels);

        /*
         * Now walk back down the tree, fixing up the cursor's buffer
         * pointers and key numbers.
         */
        for (block = xfs_btree_get_block(cur, lev, &bp); lev > level; ) {
                union xfs_btree_ptr     *ptrp;

                ptrp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[lev], block);
                --lev;
                error = xfs_btree_read_buf_block(cur, ptrp, 0, &block, &bp);
                if (error)
                        goto error0;
                xfs_btree_setbuf(cur, lev, bp);
                cur->bc_ptrs[lev] = xfs_btree_get_numrecs(block);
        }
out1:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;

out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

STATIC int
xfs_btree_lookup_get_block(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     level,  /* level in the btree */
        union xfs_btree_ptr     *pp,    /* ptr to btree block */
        struct xfs_btree_block  **blkp) /* return btree block */
{
        struct xfs_buf          *bp;    /* buffer pointer for btree block */
        int                     error = 0;

        /* special case the root block if in an inode */
        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            (level == cur->bc_nlevels - 1)) {
                *blkp = xfs_btree_get_iroot(cur);
                return 0;
        }

        /*
         * If the old buffer at this level for the disk address we are
         * looking for re-use it.
         *
         * Otherwise throw it away and get a new one.
         */
        bp = cur->bc_bufs[level];
        if (bp && XFS_BUF_ADDR(bp) == xfs_btree_ptr_to_daddr(cur, pp)) {
                *blkp = XFS_BUF_TO_BLOCK(bp);
                return 0;
        }

        error = xfs_btree_read_buf_block(cur, pp, 0, blkp, &bp);
        if (error)
                return error;

        xfs_btree_setbuf(cur, level, bp);
        return 0;
}

/*
 * Get current search key.  For level 0 we don't actually have a key
 * structure so we make one up from the record.  For all other levels
 * we just return the right key.
 */
STATIC union xfs_btree_key *
xfs_lookup_get_search_key(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     keyno,
        struct xfs_btree_block  *block,
        union xfs_btree_key     *kp)
{
        if (level == 0) {
                cur->bc_ops->init_key_from_rec(kp,
                                xfs_btree_rec_addr(cur, keyno, block));
                return kp;
        }

        return xfs_btree_key_addr(cur, keyno, block);
}

/*
 * Lookup the record.  The cursor is made to point to it, based on dir.
 * stat is set to 0 if can't find any such record, 1 for success.
 */
int                                     /* error */
xfs_btree_lookup(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_lookup_t            dir,    /* <=, ==, or >= */
        int                     *stat)  /* success/failure */
{
        struct xfs_btree_block  *block; /* current btree block */
        __int64_t               diff;   /* difference for the current key */
        int                     error;  /* error return value */
        int                     keyno;  /* current key number */
        int                     level;  /* level in the btree */
        union xfs_btree_ptr     *pp;    /* ptr to btree block */
        union xfs_btree_ptr     ptr;    /* ptr to btree block */

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, dir);

        XFS_BTREE_STATS_INC(cur, lookup);

        block = NULL;
        keyno = 0;

        /* initialise start pointer from cursor */
        cur->bc_ops->init_ptr_from_cur(cur, &ptr);
        pp = &ptr;

        /*
         * Iterate over each level in the btree, starting at the root.
         * For each level above the leaves, find the key we need, based
         * on the lookup record, then follow the corresponding block
         * pointer down to the next level.
         */
        for (level = cur->bc_nlevels - 1, diff = 1; level >= 0; level--) {
                /* Get the block we need to do the lookup on. */
                error = xfs_btree_lookup_get_block(cur, level, pp, &block);
                if (error)
                        goto error0;

                if (diff == 0) {
                        /*
                         * If we already had a key match at a higher level, we
                         * know we need to use the first entry in this block.
                         */
                        keyno = 1;
                } else {
                        /* Otherwise search this block. Do a binary search. */

                        int     high;   /* high entry number */
                        int     low;    /* low entry number */

                        /* Set low and high entry numbers, 1-based. */
                        low = 1;
                        high = xfs_btree_get_numrecs(block);
                        if (!high) {
                                /* Block is empty, must be an empty leaf. */
                                ASSERT(level == 0 && cur->bc_nlevels == 1);

                                cur->bc_ptrs[0] = dir != XFS_LOOKUP_LE;
                                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                                *stat = 0;
                                return 0;
                        }

                        /* Binary search the block. */
                        while (low <= high) {
                                union xfs_btree_key     key;
                                union xfs_btree_key     *kp;

                                XFS_BTREE_STATS_INC(cur, compare);

                                /* keyno is average of low and high. */
                                keyno = (low + high) >> 1;

                                /* Get current search key */
                                kp = xfs_lookup_get_search_key(cur, level,
                                                keyno, block, &key);

                                /*
                                 * Compute difference to get next direction:
                                 *  - less than, move right
                                 *  - greater than, move left
                                 *  - equal, we're done
                                 */
                                diff = cur->bc_ops->key_diff(cur, kp);
                                if (diff < 0)
                                        low = keyno + 1;
                                else if (diff > 0)
                                        high = keyno - 1;
                                else
                                        break;
                        }
                }

                /*
                 * If there are more levels, set up for the next level
                 * by getting the block number and filling in the cursor.
                 */
                if (level > 0) {
                        /*
                         * If we moved left, need the previous key number,
                         * unless there isn't one.
                         */
                        if (diff > 0 && --keyno < 1)
                                keyno = 1;
                        pp = xfs_btree_ptr_addr(cur, keyno, block);

#ifdef DEBUG
                        error = xfs_btree_check_ptr(cur, pp, 0, level);
                        if (error)
                                goto error0;
#endif
                        cur->bc_ptrs[level] = keyno;
                }
        }

        /* Done with the search. See if we need to adjust the results. */
        if (dir != XFS_LOOKUP_LE && diff < 0) {
                keyno++;
                /*
                 * If ge search and we went off the end of the block, but it's
                 * not the last block, we're in the wrong block.
                 */
                xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
                if (dir == XFS_LOOKUP_GE &&
                    keyno > xfs_btree_get_numrecs(block) &&
                    !xfs_btree_ptr_is_null(cur, &ptr)) {
                        int     i;

                        cur->bc_ptrs[0] = keyno;
                        error = xfs_btree_increment(cur, 0, &i);
                        if (error)
                                goto error0;
                        XFS_WANT_CORRUPTED_RETURN(cur->bc_mp, i == 1);
                        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                        *stat = 1;
                        return 0;
                }
        } else if (dir == XFS_LOOKUP_LE && diff > 0)
                keyno--;
        cur->bc_ptrs[0] = keyno;

        /* Return if we succeeded or not. */
        if (keyno == 0 || keyno > xfs_btree_get_numrecs(block))
                *stat = 0;
        else if (dir != XFS_LOOKUP_EQ || diff == 0)
                *stat = 1;
        else
                *stat = 0;
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Update keys at all levels from here to the root along the cursor's path.
 */
STATIC int
xfs_btree_updkey(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *keyp,
        int                     level)
{
        struct xfs_btree_block  *block;
        struct xfs_buf          *bp;
        union xfs_btree_key     *kp;
        int                     ptr;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGIK(cur, level, keyp);

        ASSERT(!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) || level >= 1);

        /*
         * Go up the tree from this level toward the root.
         * At each level, update the key value to the value input.
         * Stop when we reach a level where the cursor isn't pointing
         * at the first entry in the block.
         */
        for (ptr = 1; ptr == 1 && level < cur->bc_nlevels; level++) {
#ifdef DEBUG
                int             error;
#endif
                block = xfs_btree_get_block(cur, level, &bp);
#ifdef DEBUG
                error = xfs_btree_check_block(cur, block, level, bp);
                if (error) {
                        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
                        return error;
                }
#endif
                ptr = cur->bc_ptrs[level];
                kp = xfs_btree_key_addr(cur, ptr, block);
                xfs_btree_copy_keys(cur, kp, keyp, 1);
                xfs_btree_log_keys(cur, bp, ptr, ptr);
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;
}

/*
 * Update the record referred to by cur to the value in the
 * given record. This either works (return 0) or gets an
 * EFSCORRUPTED error.
 */
int
xfs_btree_update(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *rec)
{
        struct xfs_btree_block  *block;
        struct xfs_buf          *bp;
        int                     error;
        int                     ptr;
        union xfs_btree_rec     *rp;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGR(cur, rec);

        /* Pick up the current block. */
        block = xfs_btree_get_block(cur, 0, &bp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, 0, bp);
        if (error)
                goto error0;
#endif
        /* Get the address of the rec to be updated. */
        ptr = cur->bc_ptrs[0];
        rp = xfs_btree_rec_addr(cur, ptr, block);

        /* Fill in the new contents and log them. */
        xfs_btree_copy_recs(cur, rp, rec, 1);
        xfs_btree_log_recs(cur, bp, ptr, ptr);

        /*
         * If we are tracking the last record in the tree and
         * we are at the far right edge of the tree, update it.
         */
        if (xfs_btree_is_lastrec(cur, block, 0)) {
                cur->bc_ops->update_lastrec(cur, block, rec,
                                            ptr, LASTREC_UPDATE);
        }

        /* Updating first rec in leaf. Pass new key value up to our parent. */
        if (ptr == 1) {
                union xfs_btree_key     key;

                cur->bc_ops->init_key_from_rec(&key, rec);
                error = xfs_btree_updkey(cur, &key, 1);
                if (error)
                        goto error0;
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Move 1 record left from cur/level if possible.
 * Update cur to reflect the new path.
 */
STATIC int                                      /* error */
xfs_btree_lshift(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     *stat)          /* success/failure */
{
        union xfs_btree_key     key;            /* btree key */
        struct xfs_buf          *lbp;           /* left buffer pointer */
        struct xfs_btree_block  *left;          /* left btree block */
        int                     lrecs;          /* left record count */
        struct xfs_buf          *rbp;           /* right buffer pointer */
        struct xfs_btree_block  *right;         /* right btree block */
        int                     rrecs;          /* right record count */
        union xfs_btree_ptr     lptr;           /* left btree pointer */
        union xfs_btree_key     *rkp = NULL;    /* right btree key */
        union xfs_btree_ptr     *rpp = NULL;    /* right address pointer */
        union xfs_btree_rec     *rrp = NULL;    /* right record pointer */
        int                     error;          /* error return value */

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, level);

        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            level == cur->bc_nlevels - 1)
                goto out0;

        /* Set up variables for this block as "right". */
        right = xfs_btree_get_block(cur, level, &rbp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, right, level, rbp);
        if (error)
                goto error0;
#endif

        /* If we've got no left sibling then we can't shift an entry left. */
        xfs_btree_get_sibling(cur, right, &lptr, XFS_BB_LEFTSIB);
        if (xfs_btree_ptr_is_null(cur, &lptr))
                goto out0;

        /*
         * If the cursor entry is the one that would be moved, don't
         * do it... it's too complicated.
         */
        if (cur->bc_ptrs[level] <= 1)
                goto out0;

        /* Set up the left neighbor as "left". */
        error = xfs_btree_read_buf_block(cur, &lptr, 0, &left, &lbp);
        if (error)
                goto error0;

        /* If it's full, it can't take another entry. */
        lrecs = xfs_btree_get_numrecs(left);
        if (lrecs == cur->bc_ops->get_maxrecs(cur, level))
                goto out0;

        rrecs = xfs_btree_get_numrecs(right);

        /*
         * We add one entry to the left side and remove one for the right side.
         * Account for it here, the changes will be updated on disk and logged
         * later.
         */
        lrecs++;
        rrecs--;

        XFS_BTREE_STATS_INC(cur, lshift);
        XFS_BTREE_STATS_ADD(cur, moves, 1);

        /*
         * If non-leaf, copy a key and a ptr to the left block.
         * Log the changes to the left block.
         */
        if (level > 0) {
                /* It's a non-leaf.  Move keys and pointers. */
                union xfs_btree_key     *lkp;   /* left btree key */
                union xfs_btree_ptr     *lpp;   /* left address pointer */

                lkp = xfs_btree_key_addr(cur, lrecs, left);
                rkp = xfs_btree_key_addr(cur, 1, right);

                lpp = xfs_btree_ptr_addr(cur, lrecs, left);
                rpp = xfs_btree_ptr_addr(cur, 1, right);
#ifdef DEBUG
                error = xfs_btree_check_ptr(cur, rpp, 0, level);
                if (error)
                        goto error0;
#endif
                xfs_btree_copy_keys(cur, lkp, rkp, 1);
                xfs_btree_copy_ptrs(cur, lpp, rpp, 1);

                xfs_btree_log_keys(cur, lbp, lrecs, lrecs);
                xfs_btree_log_ptrs(cur, lbp, lrecs, lrecs);

                ASSERT(cur->bc_ops->keys_inorder(cur,
                        xfs_btree_key_addr(cur, lrecs - 1, left), lkp));
        } else {
                /* It's a leaf.  Move records.  */
                union xfs_btree_rec     *lrp;   /* left record pointer */

                lrp = xfs_btree_rec_addr(cur, lrecs, left);
                rrp = xfs_btree_rec_addr(cur, 1, right);

                xfs_btree_copy_recs(cur, lrp, rrp, 1);
                xfs_btree_log_recs(cur, lbp, lrecs, lrecs);

                ASSERT(cur->bc_ops->recs_inorder(cur,
                        xfs_btree_rec_addr(cur, lrecs - 1, left), lrp));
        }

        xfs_btree_set_numrecs(left, lrecs);
        xfs_btree_log_block(cur, lbp, XFS_BB_NUMRECS);

        xfs_btree_set_numrecs(right, rrecs);
        xfs_btree_log_block(cur, rbp, XFS_BB_NUMRECS);

        /*
         * Slide the contents of right down one entry.
         */
        XFS_BTREE_STATS_ADD(cur, moves, rrecs - 1);
        if (level > 0) {
                /* It's a nonleaf. operate on keys and ptrs */
#ifdef DEBUG
                int                     i;              /* loop index */

                for (i = 0; i < rrecs; i++) {
                        error = xfs_btree_check_ptr(cur, rpp, i + 1, level);
                        if (error)
                                goto error0;
                }
#endif
                xfs_btree_shift_keys(cur,
                                xfs_btree_key_addr(cur, 2, right),
                                -1, rrecs);
                xfs_btree_shift_ptrs(cur,
                                xfs_btree_ptr_addr(cur, 2, right),
                                -1, rrecs);

                xfs_btree_log_keys(cur, rbp, 1, rrecs);
                xfs_btree_log_ptrs(cur, rbp, 1, rrecs);
        } else {
                /* It's a leaf. operate on records */
                xfs_btree_shift_recs(cur,
                        xfs_btree_rec_addr(cur, 2, right),
                        -1, rrecs);
                xfs_btree_log_recs(cur, rbp, 1, rrecs);

                /*
                 * If it's the first record in the block, we'll need a key
                 * structure to pass up to the next level (updkey).
                 */
                cur->bc_ops->init_key_from_rec(&key,
                        xfs_btree_rec_addr(cur, 1, right));
                rkp = &key;
        }

        /* Update the parent key values of right. */
        error = xfs_btree_updkey(cur, rkp, level + 1);
        if (error)
                goto error0;

        /* Slide the cursor value left one. */
        cur->bc_ptrs[level]--;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;

out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Move 1 record right from cur/level if possible.
 * Update cur to reflect the new path.
 */
STATIC int                                      /* error */
xfs_btree_rshift(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     *stat)          /* success/failure */
{
        union xfs_btree_key     key;            /* btree key */
        struct xfs_buf          *lbp;           /* left buffer pointer */
        struct xfs_btree_block  *left;          /* left btree block */
        struct xfs_buf          *rbp;           /* right buffer pointer */
        struct xfs_btree_block  *right;         /* right btree block */
        struct xfs_btree_cur    *tcur;          /* temporary btree cursor */
        union xfs_btree_ptr     rptr;           /* right block pointer */
        union xfs_btree_key     *rkp;           /* right btree key */
        int                     rrecs;          /* right record count */
        int                     lrecs;          /* left record count */
        int                     error;          /* error return value */
        int                     i;              /* loop counter */

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, level);

        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            (level == cur->bc_nlevels - 1))
                goto out0;

        /* Set up variables for this block as "left". */
        left = xfs_btree_get_block(cur, level, &lbp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, left, level, lbp);
        if (error)
                goto error0;
#endif

        /* If we've got no right sibling then we can't shift an entry right. */
        xfs_btree_get_sibling(cur, left, &rptr, XFS_BB_RIGHTSIB);
        if (xfs_btree_ptr_is_null(cur, &rptr))
                goto out0;

        /*
         * If the cursor entry is the one that would be moved, don't
         * do it... it's too complicated.
         */
        lrecs = xfs_btree_get_numrecs(left);
        if (cur->bc_ptrs[level] >= lrecs)
                goto out0;

        /* Set up the right neighbor as "right". */
        error = xfs_btree_read_buf_block(cur, &rptr, 0, &right, &rbp);
        if (error)
                goto error0;

        /* If it's full, it can't take another entry. */
        rrecs = xfs_btree_get_numrecs(right);
        if (rrecs == cur->bc_ops->get_maxrecs(cur, level))
                goto out0;

        XFS_BTREE_STATS_INC(cur, rshift);
        XFS_BTREE_STATS_ADD(cur, moves, rrecs);

        /*
         * Make a hole at the start of the right neighbor block, then
         * copy the last left block entry to the hole.
         */
        if (level > 0) {
                /* It's a nonleaf. make a hole in the keys and ptrs */
                union xfs_btree_key     *lkp;
                union xfs_btree_ptr     *lpp;
                union xfs_btree_ptr     *rpp;

                lkp = xfs_btree_key_addr(cur, lrecs, left);
                lpp = xfs_btree_ptr_addr(cur, lrecs, left);
                rkp = xfs_btree_key_addr(cur, 1, right);
                rpp = xfs_btree_ptr_addr(cur, 1, right);

#ifdef DEBUG
                for (i = rrecs - 1; i >= 0; i--) {
                        error = xfs_btree_check_ptr(cur, rpp, i, level);
                        if (error)
                                goto error0;
                }
#endif

                xfs_btree_shift_keys(cur, rkp, 1, rrecs);
                xfs_btree_shift_ptrs(cur, rpp, 1, rrecs);

#ifdef DEBUG
                error = xfs_btree_check_ptr(cur, lpp, 0, level);
                if (error)
                        goto error0;
#endif

                /* Now put the new data in, and log it. */
                xfs_btree_copy_keys(cur, rkp, lkp, 1);
                xfs_btree_copy_ptrs(cur, rpp, lpp, 1);

                xfs_btree_log_keys(cur, rbp, 1, rrecs + 1);
                xfs_btree_log_ptrs(cur, rbp, 1, rrecs + 1);

                ASSERT(cur->bc_ops->keys_inorder(cur, rkp,
                        xfs_btree_key_addr(cur, 2, right)));
        } else {
                /* It's a leaf. make a hole in the records */
                union xfs_btree_rec     *lrp;
                union xfs_btree_rec     *rrp;

                lrp = xfs_btree_rec_addr(cur, lrecs, left);
                rrp = xfs_btree_rec_addr(cur, 1, right);

                xfs_btree_shift_recs(cur, rrp, 1, rrecs);

                /* Now put the new data in, and log it. */
                xfs_btree_copy_recs(cur, rrp, lrp, 1);
                xfs_btree_log_recs(cur, rbp, 1, rrecs + 1);

                cur->bc_ops->init_key_from_rec(&key, rrp);
                rkp = &key;

                ASSERT(cur->bc_ops->recs_inorder(cur, rrp,
                        xfs_btree_rec_addr(cur, 2, right)));
        }

        /*
         * Decrement and log left's numrecs, bump and log right's numrecs.
         */
        xfs_btree_set_numrecs(left, --lrecs);
        xfs_btree_log_block(cur, lbp, XFS_BB_NUMRECS);

        xfs_btree_set_numrecs(right, ++rrecs);
        xfs_btree_log_block(cur, rbp, XFS_BB_NUMRECS);

        /*
         * Using a temporary cursor, update the parent key values of the
         * block on the right.
         */
        error = xfs_btree_dup_cursor(cur, &tcur);
        if (error)
                goto error0;
        i = xfs_btree_lastrec(tcur, level);
        XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

        error = xfs_btree_increment(tcur, level, &i);
        if (error)
                goto error1;

        error = xfs_btree_updkey(tcur, rkp, level + 1);
        if (error)
                goto error1;

        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;

out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;

error1:
        XFS_BTREE_TRACE_CURSOR(tcur, XBT_ERROR);
        xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Split cur/level block in half.
 * Return new block number and the key to its first
 * record (to be inserted into parent).
 */
STATIC int                                      /* error */
__xfs_btree_split(
        struct xfs_btree_cur    *cur,
        int                     level,
        union xfs_btree_ptr     *ptrp,
        union xfs_btree_key     *key,
        struct xfs_btree_cur    **curp,
        int                     *stat)          /* success/failure */
{
        union xfs_btree_ptr     lptr;           /* left sibling block ptr */
        struct xfs_buf          *lbp;           /* left buffer pointer */
        struct xfs_btree_block  *left;          /* left btree block */
        union xfs_btree_ptr     rptr;           /* right sibling block ptr */
        struct xfs_buf          *rbp;           /* right buffer pointer */
        struct xfs_btree_block  *right;         /* right btree block */
        union xfs_btree_ptr     rrptr;          /* right-right sibling ptr */
        struct xfs_buf          *rrbp;          /* right-right buffer pointer */
        struct xfs_btree_block  *rrblock;       /* right-right btree block */
        int                     lrecs;
        int                     rrecs;
        int                     src_index;
        int                     error;          /* error return value */
#ifdef DEBUG
        int                     i;
#endif

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGIPK(cur, level, *ptrp, key);

        XFS_BTREE_STATS_INC(cur, split);

        /* Set up left block (current one). */
        left = xfs_btree_get_block(cur, level, &lbp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, left, level, lbp);
        if (error)
                goto error0;
#endif

        xfs_btree_buf_to_ptr(cur, lbp, &lptr);

        /* Allocate the new block. If we can't do it, we're toast. Give up. */
        error = cur->bc_ops->alloc_block(cur, &lptr, &rptr, stat);
        if (error)
                goto error0;
        if (*stat == 0)
                goto out0;
        XFS_BTREE_STATS_INC(cur, alloc);

        /* Set up the new block as "right". */
        error = xfs_btree_get_buf_block(cur, &rptr, 0, &right, &rbp);
        if (error)
                goto error0;

        /* Fill in the btree header for the new right block. */
        xfs_btree_init_block_cur(cur, rbp, xfs_btree_get_level(left), 0);

        /*
         * Split the entries between the old and the new block evenly.
         * Make sure that if there's an odd number of entries now, that
         * each new block will have the same number of entries.
         */
        lrecs = xfs_btree_get_numrecs(left);
        rrecs = lrecs / 2;
        if ((lrecs & 1) && cur->bc_ptrs[level] <= rrecs + 1)
                rrecs++;
        src_index = (lrecs - rrecs + 1);

        XFS_BTREE_STATS_ADD(cur, moves, rrecs);

        /*
         * Copy btree block entries from the left block over to the
         * new block, the right. Update the right block and log the
         * changes.
         */
        if (level > 0) {
                /* It's a non-leaf.  Move keys and pointers. */
                union xfs_btree_key     *lkp;   /* left btree key */
                union xfs_btree_ptr     *lpp;   /* left address pointer */
                union xfs_btree_key     *rkp;   /* right btree key */
                union xfs_btree_ptr     *rpp;   /* right address pointer */

                lkp = xfs_btree_key_addr(cur, src_index, left);
                lpp = xfs_btree_ptr_addr(cur, src_index, left);
                rkp = xfs_btree_key_addr(cur, 1, right);
                rpp = xfs_btree_ptr_addr(cur, 1, right);

#ifdef DEBUG
                for (i = src_index; i < rrecs; i++) {
                        error = xfs_btree_check_ptr(cur, lpp, i, level);
                        if (error)
                                goto error0;
                }
#endif

                xfs_btree_copy_keys(cur, rkp, lkp, rrecs);
                xfs_btree_copy_ptrs(cur, rpp, lpp, rrecs);

                xfs_btree_log_keys(cur, rbp, 1, rrecs);
                xfs_btree_log_ptrs(cur, rbp, 1, rrecs);

                /* Grab the keys to the entries moved to the right block */
                xfs_btree_copy_keys(cur, key, rkp, 1);
        } else {
                /* It's a leaf.  Move records.  */
                union xfs_btree_rec     *lrp;   /* left record pointer */
                union xfs_btree_rec     *rrp;   /* right record pointer */

                lrp = xfs_btree_rec_addr(cur, src_index, left);
                rrp = xfs_btree_rec_addr(cur, 1, right);

                xfs_btree_copy_recs(cur, rrp, lrp, rrecs);
                xfs_btree_log_recs(cur, rbp, 1, rrecs);

                cur->bc_ops->init_key_from_rec(key,
                        xfs_btree_rec_addr(cur, 1, right));
        }


        /*
         * Find the left block number by looking in the buffer.
         * Adjust numrecs, sibling pointers.
         */
        xfs_btree_get_sibling(cur, left, &rrptr, XFS_BB_RIGHTSIB);
        xfs_btree_set_sibling(cur, right, &rrptr, XFS_BB_RIGHTSIB);
        xfs_btree_set_sibling(cur, right, &lptr, XFS_BB_LEFTSIB);
        xfs_btree_set_sibling(cur, left, &rptr, XFS_BB_RIGHTSIB);

        lrecs -= rrecs;
        xfs_btree_set_numrecs(left, lrecs);
        xfs_btree_set_numrecs(right, xfs_btree_get_numrecs(right) + rrecs);

        xfs_btree_log_block(cur, rbp, XFS_BB_ALL_BITS);
        xfs_btree_log_block(cur, lbp, XFS_BB_NUMRECS | XFS_BB_RIGHTSIB);

        /*
         * If there's a block to the new block's right, make that block
         * point back to right instead of to left.
         */
        if (!xfs_btree_ptr_is_null(cur, &rrptr)) {
                error = xfs_btree_read_buf_block(cur, &rrptr,
                                                        0, &rrblock, &rrbp);
                if (error)
                        goto error0;
                xfs_btree_set_sibling(cur, rrblock, &rptr, XFS_BB_LEFTSIB);
                xfs_btree_log_block(cur, rrbp, XFS_BB_LEFTSIB);
        }
        /*
         * If the cursor is really in the right block, move it there.
         * If it's just pointing past the last entry in left, then we'll
         * insert there, so don't change anything in that case.
         */
        if (cur->bc_ptrs[level] > lrecs + 1) {
                xfs_btree_setbuf(cur, level, rbp);
                cur->bc_ptrs[level] -= lrecs;
        }
        /*
         * If there are more levels, we'll need another cursor which refers
         * the right block, no matter where this cursor was.
         */
        if (level + 1 < cur->bc_nlevels) {
                error = xfs_btree_dup_cursor(cur, curp);
                if (error)
                        goto error0;
                (*curp)->bc_ptrs[level + 1]++;
        }
        *ptrp = rptr;
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;
out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

struct xfs_btree_split_args {
        struct xfs_btree_cur    *cur;
        int                     level;
        union xfs_btree_ptr     *ptrp;
        union xfs_btree_key     *key;
        struct xfs_btree_cur    **curp;
        int                     *stat;          /* success/failure */
        int                     result;
        bool                    kswapd; /* allocation in kswapd context */
        struct completion       *done;
        struct work_struct      work;
};

/*
 * Stack switching interfaces for allocation
 */
static void
xfs_btree_split_worker(
        struct work_struct      *work)
{
        struct xfs_btree_split_args     *args = container_of(work,
                                                struct xfs_btree_split_args, work);
        unsigned long           pflags;
        unsigned long           new_pflags = PF_FSTRANS;

        /*
         * we are in a transaction context here, but may also be doing work
         * in kswapd context, and hence we may need to inherit that state
         * temporarily to ensure that we don't block waiting for memory reclaim
         * in any way.
         */
        if (args->kswapd)
                new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;

        current_set_flags_nested(&pflags, new_pflags);

        args->result = __xfs_btree_split(args->cur, args->level, args->ptrp,
                                         args->key, args->curp, args->stat);
        complete(args->done);

        current_restore_flags_nested(&pflags, new_pflags);
}

/*
 * BMBT split requests often come in with little stack to work on. Push
 * them off to a worker thread so there is lots of stack to use. For the other
 * btree types, just call directly to avoid the context switch overhead here.
 */
STATIC int                                      /* error */
xfs_btree_split(
        struct xfs_btree_cur    *cur,
        int                     level,
        union xfs_btree_ptr     *ptrp,
        union xfs_btree_key     *key,
        struct xfs_btree_cur    **curp,
        int                     *stat)          /* success/failure */
{
        struct xfs_btree_split_args     args;
        DECLARE_COMPLETION_ONSTACK(done);

        if (cur->bc_btnum != XFS_BTNUM_BMAP)
                return __xfs_btree_split(cur, level, ptrp, key, curp, stat);

        args.cur = cur;
        args.level = level;
        args.ptrp = ptrp;
        args.key = key;
        args.curp = curp;
        args.stat = stat;
        args.done = &done;
        args.kswapd = current_is_kswapd();
        INIT_WORK_ONSTACK(&args.work, xfs_btree_split_worker);
        queue_work(xfs_alloc_wq, &args.work);
        wait_for_completion(&done);
        destroy_work_on_stack(&args.work);
        return args.result;
}


/*
 * Copy the old inode root contents into a real block and make the
 * broot point to it.
 */
int                                             /* error */
xfs_btree_new_iroot(
        struct xfs_btree_cur    *cur,           /* btree cursor */
        int                     *logflags,      /* logging flags for inode */
        int                     *stat)          /* return status - 0 fail */
{
        struct xfs_buf          *cbp;           /* buffer for cblock */
        struct xfs_btree_block  *block;         /* btree block */
        struct xfs_btree_block  *cblock;        /* child btree block */
        union xfs_btree_key     *ckp;           /* child key pointer */
        union xfs_btree_ptr     *cpp;           /* child ptr pointer */
        union xfs_btree_key     *kp;            /* pointer to btree key */
        union xfs_btree_ptr     *pp;            /* pointer to block addr */
        union xfs_btree_ptr     nptr;           /* new block addr */
        int                     level;          /* btree level */
        int                     error;          /* error return code */
#ifdef DEBUG
        int                     i;              /* loop counter */
#endif

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_STATS_INC(cur, newroot);

        ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);

        level = cur->bc_nlevels - 1;

        block = xfs_btree_get_iroot(cur);
        pp = xfs_btree_ptr_addr(cur, 1, block);

        /* Allocate the new block. If we can't do it, we're toast. Give up. */
        error = cur->bc_ops->alloc_block(cur, pp, &nptr, stat);
        if (error)
                goto error0;
        if (*stat == 0) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                return 0;
        }
        XFS_BTREE_STATS_INC(cur, alloc);

        /* Copy the root into a real block. */
        error = xfs_btree_get_buf_block(cur, &nptr, 0, &cblock, &cbp);
        if (error)
                goto error0;

        /*
         * we can't just memcpy() the root in for CRC enabled btree blocks.
         * In that case have to also ensure the blkno remains correct
         */
        memcpy(cblock, block, xfs_btree_block_len(cur));
        if (cur->bc_flags & XFS_BTREE_CRC_BLOCKS) {
                if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                        cblock->bb_u.l.bb_blkno = cpu_to_be64(cbp->b_bn);
                else
                        cblock->bb_u.s.bb_blkno = cpu_to_be64(cbp->b_bn);
        }

        be16_add_cpu(&block->bb_level, 1);
        xfs_btree_set_numrecs(block, 1);
        cur->bc_nlevels++;
        cur->bc_ptrs[level + 1] = 1;

        kp = xfs_btree_key_addr(cur, 1, block);
        ckp = xfs_btree_key_addr(cur, 1, cblock);
        xfs_btree_copy_keys(cur, ckp, kp, xfs_btree_get_numrecs(cblock));

        cpp = xfs_btree_ptr_addr(cur, 1, cblock);
#ifdef DEBUG
        for (i = 0; i < be16_to_cpu(cblock->bb_numrecs); i++) {
                error = xfs_btree_check_ptr(cur, pp, i, level);
                if (error)
                        goto error0;
        }
#endif
        xfs_btree_copy_ptrs(cur, cpp, pp, xfs_btree_get_numrecs(cblock));

#ifdef DEBUG
        error = xfs_btree_check_ptr(cur, &nptr, 0, level);
        if (error)
                goto error0;
#endif
        xfs_btree_copy_ptrs(cur, pp, &nptr, 1);

        xfs_iroot_realloc(cur->bc_private.b.ip,
                          1 - xfs_btree_get_numrecs(cblock),
                          cur->bc_private.b.whichfork);

        xfs_btree_setbuf(cur, level, cbp);

        /*
         * Do all this logging at the end so that
         * the root is at the right level.
         */
        xfs_btree_log_block(cur, cbp, XFS_BB_ALL_BITS);
        xfs_btree_log_keys(cur, cbp, 1, be16_to_cpu(cblock->bb_numrecs));
        xfs_btree_log_ptrs(cur, cbp, 1, be16_to_cpu(cblock->bb_numrecs));

        *logflags |=
                XFS_ILOG_CORE | xfs_ilog_fbroot(cur->bc_private.b.whichfork);
        *stat = 1;
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;
error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Allocate a new root block, fill it in.
 */
STATIC int                              /* error */
xfs_btree_new_root(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     *stat)  /* success/failure */
{
        struct xfs_btree_block  *block; /* one half of the old root block */
        struct xfs_buf          *bp;    /* buffer containing block */
        int                     error;  /* error return value */
        struct xfs_buf          *lbp;   /* left buffer pointer */
        struct xfs_btree_block  *left;  /* left btree block */
        struct xfs_buf          *nbp;   /* new (root) buffer */
        struct xfs_btree_block  *new;   /* new (root) btree block */
        int                     nptr;   /* new value for key index, 1 or 2 */
        struct xfs_buf          *rbp;   /* right buffer pointer */
        struct xfs_btree_block  *right; /* right btree block */
        union xfs_btree_ptr     rptr;
        union xfs_btree_ptr     lptr;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_STATS_INC(cur, newroot);

        /* initialise our start point from the cursor */
        cur->bc_ops->init_ptr_from_cur(cur, &rptr);

        /* Allocate the new block. If we can't do it, we're toast. Give up. */
        error = cur->bc_ops->alloc_block(cur, &rptr, &lptr, stat);
        if (error)
                goto error0;
        if (*stat == 0)
                goto out0;
        XFS_BTREE_STATS_INC(cur, alloc);

        /* Set up the new block. */
        error = xfs_btree_get_buf_block(cur, &lptr, 0, &new, &nbp);
        if (error)
                goto error0;

        /* Set the root in the holding structure  increasing the level by 1. */
        cur->bc_ops->set_root(cur, &lptr, 1);

        /*
         * At the previous root level there are now two blocks: the old root,
         * and the new block generated when it was split.  We don't know which
         * one the cursor is pointing at, so we set up variables "left" and
         * "right" for each case.
         */
        block = xfs_btree_get_block(cur, cur->bc_nlevels - 1, &bp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, cur->bc_nlevels - 1, bp);
        if (error)
                goto error0;
#endif

        xfs_btree_get_sibling(cur, block, &rptr, XFS_BB_RIGHTSIB);
        if (!xfs_btree_ptr_is_null(cur, &rptr)) {
                /* Our block is left, pick up the right block. */
                lbp = bp;
                xfs_btree_buf_to_ptr(cur, lbp, &lptr);
                left = block;
                error = xfs_btree_read_buf_block(cur, &rptr, 0, &right, &rbp);
                if (error)
                        goto error0;
                bp = rbp;
                nptr = 1;
        } else {
                /* Our block is right, pick up the left block. */
                rbp = bp;
                xfs_btree_buf_to_ptr(cur, rbp, &rptr);
                right = block;
                xfs_btree_get_sibling(cur, right, &lptr, XFS_BB_LEFTSIB);
                error = xfs_btree_read_buf_block(cur, &lptr, 0, &left, &lbp);
                if (error)
                        goto error0;
                bp = lbp;
                nptr = 2;
        }
        /* Fill in the new block's btree header and log it. */
        xfs_btree_init_block_cur(cur, nbp, cur->bc_nlevels, 2);
        xfs_btree_log_block(cur, nbp, XFS_BB_ALL_BITS);
        ASSERT(!xfs_btree_ptr_is_null(cur, &lptr) &&
                        !xfs_btree_ptr_is_null(cur, &rptr));

        /* Fill in the key data in the new root. */
        if (xfs_btree_get_level(left) > 0) {
                xfs_btree_copy_keys(cur,
                                xfs_btree_key_addr(cur, 1, new),
                                xfs_btree_key_addr(cur, 1, left), 1);
                xfs_btree_copy_keys(cur,
                                xfs_btree_key_addr(cur, 2, new),
                                xfs_btree_key_addr(cur, 1, right), 1);
        } else {
                cur->bc_ops->init_key_from_rec(
                                xfs_btree_key_addr(cur, 1, new),
                                xfs_btree_rec_addr(cur, 1, left));
                cur->bc_ops->init_key_from_rec(
                                xfs_btree_key_addr(cur, 2, new),
                                xfs_btree_rec_addr(cur, 1, right));
        }
        xfs_btree_log_keys(cur, nbp, 1, 2);

        /* Fill in the pointer data in the new root. */
        xfs_btree_copy_ptrs(cur,
                xfs_btree_ptr_addr(cur, 1, new), &lptr, 1);
        xfs_btree_copy_ptrs(cur,
                xfs_btree_ptr_addr(cur, 2, new), &rptr, 1);
        xfs_btree_log_ptrs(cur, nbp, 1, 2);

        /* Fix up the cursor. */
        xfs_btree_setbuf(cur, cur->bc_nlevels, nbp);
        cur->bc_ptrs[cur->bc_nlevels] = nptr;
        cur->bc_nlevels++;
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;
error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;
}

STATIC int
xfs_btree_make_block_unfull(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     level,  /* btree level */
        int                     numrecs,/* # of recs in block */
        int                     *oindex,/* old tree index */
        int                     *index, /* new tree index */
        union xfs_btree_ptr     *nptr,  /* new btree ptr */
        struct xfs_btree_cur    **ncur, /* new btree cursor */
        union xfs_btree_rec     *nrec,  /* new record */
        int                     *stat)
{
        union xfs_btree_key     key;    /* new btree key value */
        int                     error = 0;

        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            level == cur->bc_nlevels - 1) {
                struct xfs_inode *ip = cur->bc_private.b.ip;

                if (numrecs < cur->bc_ops->get_dmaxrecs(cur, level)) {
                        /* A root block that can be made bigger. */
                        xfs_iroot_realloc(ip, 1, cur->bc_private.b.whichfork);
                } else {
                        /* A root block that needs replacing */
                        int     logflags = 0;

                        error = xfs_btree_new_iroot(cur, &logflags, stat);
                        if (error || *stat == 0)
                                return error;

                        xfs_trans_log_inode(cur->bc_tp, ip, logflags);
                }

                return 0;
        }

        /* First, try shifting an entry to the right neighbor. */
        error = xfs_btree_rshift(cur, level, stat);
        if (error || *stat)
                return error;

        /* Next, try shifting an entry to the left neighbor. */
        error = xfs_btree_lshift(cur, level, stat);
        if (error)
                return error;

        if (*stat) {
                *oindex = *index = cur->bc_ptrs[level];
                return 0;
        }

        /*
         * Next, try splitting the current block in half.
         *
         * If this works we have to re-set our variables because we
         * could be in a different block now.
         */
        error = xfs_btree_split(cur, level, nptr, &key, ncur, stat);
        if (error || *stat == 0)
                return error;


        *index = cur->bc_ptrs[level];
        cur->bc_ops->init_rec_from_key(&key, nrec);
        return 0;
}

/*
 * Insert one record/level.  Return information to the caller
 * allowing the next level up to proceed if necessary.
 */
STATIC int
xfs_btree_insrec(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     level,  /* level to insert record at */
        union xfs_btree_ptr     *ptrp,  /* i/o: block number inserted */
        union xfs_btree_rec     *recp,  /* i/o: record data inserted */
        struct xfs_btree_cur    **curp, /* output: new cursor replacing cur */
        int                     *stat)  /* success/failure */
{
        struct xfs_btree_block  *block; /* btree block */
        struct xfs_buf          *bp;    /* buffer for block */
        union xfs_btree_key     key;    /* btree key */
        union xfs_btree_ptr     nptr;   /* new block ptr */
        struct xfs_btree_cur    *ncur;  /* new btree cursor */
        union xfs_btree_rec     nrec;   /* new record count */
        int                     optr;   /* old key/record index */
        int                     ptr;    /* key/record index */
        int                     numrecs;/* number of records */
        int                     error;  /* error return value */
#ifdef DEBUG
        int                     i;
#endif

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGIPR(cur, level, *ptrp, recp);

        ncur = NULL;

        /*
         * If we have an external root pointer, and we've made it to the
         * root level, allocate a new root block and we're done.
         */
        if (!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
            (level >= cur->bc_nlevels)) {
                error = xfs_btree_new_root(cur, stat);
                xfs_btree_set_ptr_null(cur, ptrp);

                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                return error;
        }

        /* If we're off the left edge, return failure. */
        ptr = cur->bc_ptrs[level];
        if (ptr == 0) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                *stat = 0;
                return 0;
        }

        /* Make a key out of the record data to be inserted, and save it. */
        cur->bc_ops->init_key_from_rec(&key, recp);

        optr = ptr;

        XFS_BTREE_STATS_INC(cur, insrec);

        /* Get pointers to the btree buffer and block. */
        block = xfs_btree_get_block(cur, level, &bp);
        numrecs = xfs_btree_get_numrecs(block);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, level, bp);
        if (error)
                goto error0;

        /* Check that the new entry is being inserted in the right place. */
        if (ptr <= numrecs) {
                if (level == 0) {
                        ASSERT(cur->bc_ops->recs_inorder(cur, recp,
                                xfs_btree_rec_addr(cur, ptr, block)));
                } else {
                        ASSERT(cur->bc_ops->keys_inorder(cur, &key,
                                xfs_btree_key_addr(cur, ptr, block)));
                }
        }
#endif

        /*
         * If the block is full, we can't insert the new entry until we
         * make the block un-full.
         */
        xfs_btree_set_ptr_null(cur, &nptr);
        if (numrecs == cur->bc_ops->get_maxrecs(cur, level)) {
                error = xfs_btree_make_block_unfull(cur, level, numrecs,
                                        &optr, &ptr, &nptr, &ncur, &nrec, stat);
                if (error || *stat == 0)
                        goto error0;
        }

        /*
         * The current block may have changed if the block was
         * previously full and we have just made space in it.
         */
        block = xfs_btree_get_block(cur, level, &bp);
        numrecs = xfs_btree_get_numrecs(block);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, level, bp);
        if (error)
                return error;
#endif

        /*
         * At this point we know there's room for our new entry in the block
         * we're pointing at.
         */
        XFS_BTREE_STATS_ADD(cur, moves, numrecs - ptr + 1);

        if (level > 0) {
                /* It's a nonleaf. make a hole in the keys and ptrs */
                union xfs_btree_key     *kp;
                union xfs_btree_ptr     *pp;

                kp = xfs_btree_key_addr(cur, ptr, block);
                pp = xfs_btree_ptr_addr(cur, ptr, block);

#ifdef DEBUG
                for (i = numrecs - ptr; i >= 0; i--) {
                        error = xfs_btree_check_ptr(cur, pp, i, level);
                        if (error)
                                return error;
                }
#endif

                xfs_btree_shift_keys(cur, kp, 1, numrecs - ptr + 1);
                xfs_btree_shift_ptrs(cur, pp, 1, numrecs - ptr + 1);

#ifdef DEBUG
                error = xfs_btree_check_ptr(cur, ptrp, 0, level);
                if (error)
                        goto error0;
#endif

                /* Now put the new data in, bump numrecs and log it. */
                xfs_btree_copy_keys(cur, kp, &key, 1);
                xfs_btree_copy_ptrs(cur, pp, ptrp, 1);
                numrecs++;
                xfs_btree_set_numrecs(block, numrecs);
                xfs_btree_log_ptrs(cur, bp, ptr, numrecs);
                xfs_btree_log_keys(cur, bp, ptr, numrecs);
#ifdef DEBUG
                if (ptr < numrecs) {
                        ASSERT(cur->bc_ops->keys_inorder(cur, kp,
                                xfs_btree_key_addr(cur, ptr + 1, block)));
                }
#endif
        } else {
                /* It's a leaf. make a hole in the records */
                union xfs_btree_rec             *rp;

                rp = xfs_btree_rec_addr(cur, ptr, block);

                xfs_btree_shift_recs(cur, rp, 1, numrecs - ptr + 1);

                /* Now put the new data in, bump numrecs and log it. */
                xfs_btree_copy_recs(cur, rp, recp, 1);
                xfs_btree_set_numrecs(block, ++numrecs);
                xfs_btree_log_recs(cur, bp, ptr, numrecs);
#ifdef DEBUG
                if (ptr < numrecs) {
                        ASSERT(cur->bc_ops->recs_inorder(cur, rp,
                                xfs_btree_rec_addr(cur, ptr + 1, block)));
                }
#endif
        }

        /* Log the new number of records in the btree header. */
        xfs_btree_log_block(cur, bp, XFS_BB_NUMRECS);

        /* If we inserted at the start of a block, update the parents' keys. */
        if (optr == 1) {
                error = xfs_btree_updkey(cur, &key, level + 1);
                if (error)
                        goto error0;
        }

        /*
         * If we are tracking the last record in the tree and
         * we are at the far right edge of the tree, update it.
         */
        if (xfs_btree_is_lastrec(cur, block, level)) {
                cur->bc_ops->update_lastrec(cur, block, recp,
                                            ptr, LASTREC_INSREC);
        }

        /*
         * Return the new block number, if any.
         * If there is one, give back a record value and a cursor too.
         */
        *ptrp = nptr;
        if (!xfs_btree_ptr_is_null(cur, &nptr)) {
                *recp = nrec;
                *curp = ncur;
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Insert the record at the point referenced by cur.
 *
 * A multi-level split of the tree on insert will invalidate the original
 * cursor.  All callers of this function should assume that the cursor is
 * no longer valid and revalidate it.
 */
int
xfs_btree_insert(
        struct xfs_btree_cur    *cur,
        int                     *stat)
{
        int                     error;  /* error return value */
        int                     i;      /* result value, 0 for failure */
        int                     level;  /* current level number in btree */
        union xfs_btree_ptr     nptr;   /* new block number (split result) */
        struct xfs_btree_cur    *ncur;  /* new cursor (split result) */
        struct xfs_btree_cur    *pcur;  /* previous level's cursor */
        union xfs_btree_rec     rec;    /* record to insert */

        level = 0;
        ncur = NULL;
        pcur = cur;

        xfs_btree_set_ptr_null(cur, &nptr);
        cur->bc_ops->init_rec_from_cur(cur, &rec);

        /*
         * Loop going up the tree, starting at the leaf level.
         * Stop when we don't get a split block, that must mean that
         * the insert is finished with this level.
         */
        do {
                /*
                 * Insert nrec/nptr into this level of the tree.
                 * Note if we fail, nptr will be null.
                 */
                error = xfs_btree_insrec(pcur, level, &nptr, &rec, &ncur, &i);
                if (error) {
                        if (pcur != cur)
                                xfs_btree_del_cursor(pcur, XFS_BTREE_ERROR);
                        goto error0;
                }

                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);
                level++;

                /*
                 * See if the cursor we just used is trash.
                 * Can't trash the caller's cursor, but otherwise we should
                 * if ncur is a new cursor or we're about to be done.
                 */
                if (pcur != cur &&
                    (ncur || xfs_btree_ptr_is_null(cur, &nptr))) {
                        /* Save the state from the cursor before we trash it */
                        if (cur->bc_ops->update_cursor)
                                cur->bc_ops->update_cursor(pcur, cur);
                        cur->bc_nlevels = pcur->bc_nlevels;
                        xfs_btree_del_cursor(pcur, XFS_BTREE_NOERROR);
                }
                /* If we got a new cursor, switch to it. */
                if (ncur) {
                        pcur = ncur;
                        ncur = NULL;
                }
        } while (!xfs_btree_ptr_is_null(cur, &nptr));

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = i;
        return 0;
error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Try to merge a non-leaf block back into the inode root.
 *
 * Note: the killroot names comes from the fact that we're effectively
 * killing the old root block.  But because we can't just delete the
 * inode we have to copy the single block it was pointing to into the
 * inode.
 */
STATIC int
xfs_btree_kill_iroot(
        struct xfs_btree_cur    *cur)
{
        int                     whichfork = cur->bc_private.b.whichfork;
        struct xfs_inode        *ip = cur->bc_private.b.ip;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_btree_block  *block;
        struct xfs_btree_block  *cblock;
        union xfs_btree_key     *kp;
        union xfs_btree_key     *ckp;
        union xfs_btree_ptr     *pp;
        union xfs_btree_ptr     *cpp;
        struct xfs_buf          *cbp;
        int                     level;
        int                     index;
        int                     numrecs;
        int                     error;
#ifdef DEBUG
        union xfs_btree_ptr     ptr;
        int                     i;
#endif

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);

        ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);
        ASSERT(cur->bc_nlevels > 1);

        /*
         * Don't deal with the root block needs to be a leaf case.
         * We're just going to turn the thing back into extents anyway.
         */
        level = cur->bc_nlevels - 1;
        if (level == 1)
                goto out0;

        /*
         * Give up if the root has multiple children.
         */
        block = xfs_btree_get_iroot(cur);
        if (xfs_btree_get_numrecs(block) != 1)
                goto out0;

        cblock = xfs_btree_get_block(cur, level - 1, &cbp);
        numrecs = xfs_btree_get_numrecs(cblock);

        /*
         * Only do this if the next level will fit.
         * Then the data must be copied up to the inode,
         * instead of freeing the root you free the next level.
         */
        if (numrecs > cur->bc_ops->get_dmaxrecs(cur, level))
                goto out0;

        XFS_BTREE_STATS_INC(cur, killroot);

#ifdef DEBUG
        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_LEFTSIB);
        ASSERT(xfs_btree_ptr_is_null(cur, &ptr));
        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
        ASSERT(xfs_btree_ptr_is_null(cur, &ptr));
#endif

        index = numrecs - cur->bc_ops->get_maxrecs(cur, level);
        if (index) {
                xfs_iroot_realloc(cur->bc_private.b.ip, index,
                                  cur->bc_private.b.whichfork);
                block = ifp->if_broot;
        }

        be16_add_cpu(&block->bb_numrecs, index);
        ASSERT(block->bb_numrecs == cblock->bb_numrecs);

        kp = xfs_btree_key_addr(cur, 1, block);
        ckp = xfs_btree_key_addr(cur, 1, cblock);
        xfs_btree_copy_keys(cur, kp, ckp, numrecs);

        pp = xfs_btree_ptr_addr(cur, 1, block);
        cpp = xfs_btree_ptr_addr(cur, 1, cblock);
#ifdef DEBUG
        for (i = 0; i < numrecs; i++) {
                error = xfs_btree_check_ptr(cur, cpp, i, level - 1);
                if (error) {
                        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
                        return error;
                }
        }
#endif
        xfs_btree_copy_ptrs(cur, pp, cpp, numrecs);

        error = xfs_btree_free_block(cur, cbp);
        if (error) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
                return error;
        }

        cur->bc_bufs[level - 1] = NULL;
        be16_add_cpu(&block->bb_level, -1);
        xfs_trans_log_inode(cur->bc_tp, ip,
                XFS_ILOG_CORE | xfs_ilog_fbroot(cur->bc_private.b.whichfork));
        cur->bc_nlevels--;
out0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;
}

/*
 * Kill the current root node, and replace it with it's only child node.
 */
STATIC int
xfs_btree_kill_root(
        struct xfs_btree_cur    *cur,
        struct xfs_buf          *bp,
        int                     level,
        union xfs_btree_ptr     *newroot)
{
        int                     error;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_STATS_INC(cur, killroot);

        /*
         * Update the root pointer, decreasing the level by 1 and then
         * free the old root.
         */
        cur->bc_ops->set_root(cur, newroot, -1);

        error = xfs_btree_free_block(cur, bp);
        if (error) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
                return error;
        }

        cur->bc_bufs[level] = NULL;
        cur->bc_ra[level] = 0;
        cur->bc_nlevels--;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        return 0;
}

STATIC int
xfs_btree_dec_cursor(
        struct xfs_btree_cur    *cur,
        int                     level,
        int                     *stat)
{
        int                     error;
        int                     i;

        if (level > 0) {
                error = xfs_btree_decrement(cur, level, &i);
                if (error)
                        return error;
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 1;
        return 0;
}

/*
 * Single level of the btree record deletion routine.
 * Delete record pointed to by cur/level.
 * Remove the record from its block then rebalance the tree.
 * Return 0 for error, 1 for done, 2 to go on to the next level.
 */
STATIC int                                      /* error */
xfs_btree_delrec(
        struct xfs_btree_cur    *cur,           /* btree cursor */
        int                     level,          /* level removing record from */
        int                     *stat)          /* fail/done/go-on */
{
        struct xfs_btree_block  *block;         /* btree block */
        union xfs_btree_ptr     cptr;           /* current block ptr */
        struct xfs_buf          *bp;            /* buffer for block */
        int                     error;          /* error return value */
        int                     i;              /* loop counter */
        union xfs_btree_key     key;            /* storage for keyp */
        union xfs_btree_key     *keyp = &key;   /* passed to the next level */
        union xfs_btree_ptr     lptr;           /* left sibling block ptr */
        struct xfs_buf          *lbp;           /* left buffer pointer */
        struct xfs_btree_block  *left;          /* left btree block */
        int                     lrecs = 0;      /* left record count */
        int                     ptr;            /* key/record index */
        union xfs_btree_ptr     rptr;           /* right sibling block ptr */
        struct xfs_buf          *rbp;           /* right buffer pointer */
        struct xfs_btree_block  *right;         /* right btree block */
        struct xfs_btree_block  *rrblock;       /* right-right btree block */
        struct xfs_buf          *rrbp;          /* right-right buffer pointer */
        int                     rrecs = 0;      /* right record count */
        struct xfs_btree_cur    *tcur;          /* temporary btree cursor */
        int                     numrecs;        /* temporary numrec count */

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
        XFS_BTREE_TRACE_ARGI(cur, level);

        tcur = NULL;

        /* Get the index of the entry being deleted, check for nothing there. */
        ptr = cur->bc_ptrs[level];
        if (ptr == 0) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                *stat = 0;
                return 0;
        }

        /* Get the buffer & block containing the record or key/ptr. */
        block = xfs_btree_get_block(cur, level, &bp);
        numrecs = xfs_btree_get_numrecs(block);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, level, bp);
        if (error)
                goto error0;
#endif

        /* Fail if we're off the end of the block. */
        if (ptr > numrecs) {
                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                *stat = 0;
                return 0;
        }

        XFS_BTREE_STATS_INC(cur, delrec);
        XFS_BTREE_STATS_ADD(cur, moves, numrecs - ptr);

        /* Excise the entries being deleted. */
        if (level > 0) {
                /* It's a nonleaf. operate on keys and ptrs */
                union xfs_btree_key     *lkp;
                union xfs_btree_ptr     *lpp;

                lkp = xfs_btree_key_addr(cur, ptr + 1, block);
                lpp = xfs_btree_ptr_addr(cur, ptr + 1, block);

#ifdef DEBUG
                for (i = 0; i < numrecs - ptr; i++) {
                        error = xfs_btree_check_ptr(cur, lpp, i, level);
                        if (error)
                                goto error0;
                }
#endif

                if (ptr < numrecs) {
                        xfs_btree_shift_keys(cur, lkp, -1, numrecs - ptr);
                        xfs_btree_shift_ptrs(cur, lpp, -1, numrecs - ptr);
                        xfs_btree_log_keys(cur, bp, ptr, numrecs - 1);
                        xfs_btree_log_ptrs(cur, bp, ptr, numrecs - 1);
                }

                /*
                 * If it's the first record in the block, we'll need to pass a
                 * key up to the next level (updkey).
                 */
                if (ptr == 1)
                        keyp = xfs_btree_key_addr(cur, 1, block);
        } else {
                /* It's a leaf. operate on records */
                if (ptr < numrecs) {
                        xfs_btree_shift_recs(cur,
                                xfs_btree_rec_addr(cur, ptr + 1, block),
                                -1, numrecs - ptr);
                        xfs_btree_log_recs(cur, bp, ptr, numrecs - 1);
                }

                /*
                 * If it's the first record in the block, we'll need a key
                 * structure to pass up to the next level (updkey).
                 */
                if (ptr == 1) {
                        cur->bc_ops->init_key_from_rec(&key,
                                        xfs_btree_rec_addr(cur, 1, block));
                        keyp = &key;
                }
        }

        /*
         * Decrement and log the number of entries in the block.
         */
        xfs_btree_set_numrecs(block, --numrecs);
        xfs_btree_log_block(cur, bp, XFS_BB_NUMRECS);

        /*
         * If we are tracking the last record in the tree and
         * we are at the far right edge of the tree, update it.
         */
        if (xfs_btree_is_lastrec(cur, block, level)) {
                cur->bc_ops->update_lastrec(cur, block, NULL,
                                            ptr, LASTREC_DELREC);
        }

        /*
         * We're at the root level.  First, shrink the root block in-memory.
         * Try to get rid of the next level down.  If we can't then there's
         * nothing left to do.
         */
        if (level == cur->bc_nlevels - 1) {
                if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) {
                        xfs_iroot_realloc(cur->bc_private.b.ip, -1,
                                          cur->bc_private.b.whichfork);

                        error = xfs_btree_kill_iroot(cur);
                        if (error)
                                goto error0;

                        error = xfs_btree_dec_cursor(cur, level, stat);
                        if (error)
                                goto error0;
                        *stat = 1;
                        return 0;
                }

                /*
                 * If this is the root level, and there's only one entry left,
                 * and it's NOT the leaf level, then we can get rid of this
                 * level.
                 */
                if (numrecs == 1 && level > 0) {
                        union xfs_btree_ptr     *pp;
                        /*
                         * pp is still set to the first pointer in the block.
                         * Make it the new root of the btree.
                         */
                        pp = xfs_btree_ptr_addr(cur, 1, block);
                        error = xfs_btree_kill_root(cur, bp, level, pp);
                        if (error)
                                goto error0;
                } else if (level > 0) {
                        error = xfs_btree_dec_cursor(cur, level, stat);
                        if (error)
                                goto error0;
                }
                *stat = 1;
                return 0;
        }

        /*
         * If we deleted the leftmost entry in the block, update the
         * key values above us in the tree.
         */
        if (ptr == 1) {
                error = xfs_btree_updkey(cur, keyp, level + 1);
                if (error)
                        goto error0;
        }

        /*
         * If the number of records remaining in the block is at least
         * the minimum, we're done.
         */
        if (numrecs >= cur->bc_ops->get_minrecs(cur, level)) {
                error = xfs_btree_dec_cursor(cur, level, stat);
                if (error)
                        goto error0;
                return 0;
        }

        /*
         * Otherwise, we have to move some records around to keep the
         * tree balanced.  Look at the left and right sibling blocks to
         * see if we can re-balance by moving only one record.
         */
        xfs_btree_get_sibling(cur, block, &rptr, XFS_BB_RIGHTSIB);
        xfs_btree_get_sibling(cur, block, &lptr, XFS_BB_LEFTSIB);

        if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) {
                /*
                 * One child of root, need to get a chance to copy its contents
                 * into the root and delete it. Can't go up to next level,
                 * there's nothing to delete there.
                 */
                if (xfs_btree_ptr_is_null(cur, &rptr) &&
                    xfs_btree_ptr_is_null(cur, &lptr) &&
                    level == cur->bc_nlevels - 2) {
                        error = xfs_btree_kill_iroot(cur);
                        if (!error)
                                error = xfs_btree_dec_cursor(cur, level, stat);
                        if (error)
                                goto error0;
                        return 0;
                }
        }

        ASSERT(!xfs_btree_ptr_is_null(cur, &rptr) ||
               !xfs_btree_ptr_is_null(cur, &lptr));

        /*
         * Duplicate the cursor so our btree manipulations here won't
         * disrupt the next level up.
         */
        error = xfs_btree_dup_cursor(cur, &tcur);
        if (error)
                goto error0;

        /*
         * If there's a right sibling, see if it's ok to shift an entry
         * out of it.
         */
        if (!xfs_btree_ptr_is_null(cur, &rptr)) {
                /*
                 * Move the temp cursor to the last entry in the next block.
                 * Actually any entry but the first would suffice.
                 */
                i = xfs_btree_lastrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                error = xfs_btree_increment(tcur, level, &i);
                if (error)
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                i = xfs_btree_lastrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                /* Grab a pointer to the block. */
                right = xfs_btree_get_block(tcur, level, &rbp);
#ifdef DEBUG
                error = xfs_btree_check_block(tcur, right, level, rbp);
                if (error)
                        goto error0;
#endif
                /* Grab the current block number, for future use. */
                xfs_btree_get_sibling(tcur, right, &cptr, XFS_BB_LEFTSIB);

                /*
                 * If right block is full enough so that removing one entry
                 * won't make it too empty, and left-shifting an entry out
                 * of right to us works, we're done.
                 */
                if (xfs_btree_get_numrecs(right) - 1 >=
                    cur->bc_ops->get_minrecs(tcur, level)) {
                        error = xfs_btree_lshift(tcur, level, &i);
                        if (error)
                                goto error0;
                        if (i) {
                                ASSERT(xfs_btree_get_numrecs(block) >=
                                       cur->bc_ops->get_minrecs(tcur, level));

                                xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
                                tcur = NULL;

                                error = xfs_btree_dec_cursor(cur, level, stat);
                                if (error)
                                        goto error0;
                                return 0;
                        }
                }

                /*
                 * Otherwise, grab the number of records in right for
                 * future reference, and fix up the temp cursor to point
                 * to our block again (last record).
                 */
                rrecs = xfs_btree_get_numrecs(right);
                if (!xfs_btree_ptr_is_null(cur, &lptr)) {
                        i = xfs_btree_firstrec(tcur, level);
                        XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                        error = xfs_btree_decrement(tcur, level, &i);
                        if (error)
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);
                }
        }

        /*
         * If there's a left sibling, see if it's ok to shift an entry
         * out of it.
         */
        if (!xfs_btree_ptr_is_null(cur, &lptr)) {
                /*
                 * Move the temp cursor to the first entry in the
                 * previous block.
                 */
                i = xfs_btree_firstrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                error = xfs_btree_decrement(tcur, level, &i);
                if (error)
                        goto error0;
                i = xfs_btree_firstrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(cur->bc_mp, i == 1, error0);

                /* Grab a pointer to the block. */
                left = xfs_btree_get_block(tcur, level, &lbp);
#ifdef DEBUG
                error = xfs_btree_check_block(cur, left, level, lbp);
                if (error)
                        goto error0;
#endif
                /* Grab the current block number, for future use. */
                xfs_btree_get_sibling(tcur, left, &cptr, XFS_BB_RIGHTSIB);

                /*
                 * If left block is full enough so that removing one entry
                 * won't make it too empty, and right-shifting an entry out
                 * of left to us works, we're done.
                 */
                if (xfs_btree_get_numrecs(left) - 1 >=
                    cur->bc_ops->get_minrecs(tcur, level)) {
                        error = xfs_btree_rshift(tcur, level, &i);
                        if (error)
                                goto error0;
                        if (i) {
                                ASSERT(xfs_btree_get_numrecs(block) >=
                                       cur->bc_ops->get_minrecs(tcur, level));
                                xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
                                tcur = NULL;
                                if (level == 0)
                                        cur->bc_ptrs[0]++;
                                XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
                                *stat = 1;
                                return 0;
                        }
                }

                /*
                 * Otherwise, grab the number of records in right for
                 * future reference.
                 */
                lrecs = xfs_btree_get_numrecs(left);
        }

        /* Delete the temp cursor, we're done with it. */
        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
        tcur = NULL;

        /* If here, we need to do a join to keep the tree balanced. */
        ASSERT(!xfs_btree_ptr_is_null(cur, &cptr));

        if (!xfs_btree_ptr_is_null(cur, &lptr) &&
            lrecs + xfs_btree_get_numrecs(block) <=
                        cur->bc_ops->get_maxrecs(cur, level)) {
                /*
                 * Set "right" to be the starting block,
                 * "left" to be the left neighbor.
                 */
                rptr = cptr;
                right = block;
                rbp = bp;
                error = xfs_btree_read_buf_block(cur, &lptr, 0, &left, &lbp);
                if (error)
                        goto error0;

        /*
         * If that won't work, see if we can join with the right neighbor block.
         */
        } else if (!xfs_btree_ptr_is_null(cur, &rptr) &&
                   rrecs + xfs_btree_get_numrecs(block) <=
                        cur->bc_ops->get_maxrecs(cur, level)) {
                /*
                 * Set "left" to be the starting block,
                 * "right" to be the right neighbor.
                 */
                lptr = cptr;
                left = block;
                lbp = bp;
                error = xfs_btree_read_buf_block(cur, &rptr, 0, &right, &rbp);
                if (error)
                        goto error0;

        /*
         * Otherwise, we can't fix the imbalance.
         * Just return.  This is probably a logic error, but it's not fatal.
         */
        } else {
                error = xfs_btree_dec_cursor(cur, level, stat);
                if (error)
                        goto error0;
                return 0;
        }

        rrecs = xfs_btree_get_numrecs(right);
        lrecs = xfs_btree_get_numrecs(left);

        /*
         * We're now going to join "left" and "right" by moving all the stuff
         * in "right" to "left" and deleting "right".
         */
        XFS_BTREE_STATS_ADD(cur, moves, rrecs);
        if (level > 0) {
                /* It's a non-leaf.  Move keys and pointers. */
                union xfs_btree_key     *lkp;   /* left btree key */
                union xfs_btree_ptr     *lpp;   /* left address pointer */
                union xfs_btree_key     *rkp;   /* right btree key */
                union xfs_btree_ptr     *rpp;   /* right address pointer */

                lkp = xfs_btree_key_addr(cur, lrecs + 1, left);
                lpp = xfs_btree_ptr_addr(cur, lrecs + 1, left);
                rkp = xfs_btree_key_addr(cur, 1, right);
                rpp = xfs_btree_ptr_addr(cur, 1, right);
#ifdef DEBUG
                for (i = 1; i < rrecs; i++) {
                        error = xfs_btree_check_ptr(cur, rpp, i, level);
                        if (error)
                                goto error0;
                }
#endif
                xfs_btree_copy_keys(cur, lkp, rkp, rrecs);
                xfs_btree_copy_ptrs(cur, lpp, rpp, rrecs);

                xfs_btree_log_keys(cur, lbp, lrecs + 1, lrecs + rrecs);
                xfs_btree_log_ptrs(cur, lbp, lrecs + 1, lrecs + rrecs);
        } else {
                /* It's a leaf.  Move records.  */
                union xfs_btree_rec     *lrp;   /* left record pointer */
                union xfs_btree_rec     *rrp;   /* right record pointer */

                lrp = xfs_btree_rec_addr(cur, lrecs + 1, left);
                rrp = xfs_btree_rec_addr(cur, 1, right);

                xfs_btree_copy_recs(cur, lrp, rrp, rrecs);
                xfs_btree_log_recs(cur, lbp, lrecs + 1, lrecs + rrecs);
        }

        XFS_BTREE_STATS_INC(cur, join);

        /*
         * Fix up the number of records and right block pointer in the
         * surviving block, and log it.
         */
        xfs_btree_set_numrecs(left, lrecs + rrecs);
        xfs_btree_get_sibling(cur, right, &cptr, XFS_BB_RIGHTSIB),
        xfs_btree_set_sibling(cur, left, &cptr, XFS_BB_RIGHTSIB);
        xfs_btree_log_block(cur, lbp, XFS_BB_NUMRECS | XFS_BB_RIGHTSIB);

        /* If there is a right sibling, point it to the remaining block. */
        xfs_btree_get_sibling(cur, left, &cptr, XFS_BB_RIGHTSIB);
        if (!xfs_btree_ptr_is_null(cur, &cptr)) {
                error = xfs_btree_read_buf_block(cur, &cptr, 0, &rrblock, &rrbp);
                if (error)
                        goto error0;
                xfs_btree_set_sibling(cur, rrblock, &lptr, XFS_BB_LEFTSIB);
                xfs_btree_log_block(cur, rrbp, XFS_BB_LEFTSIB);
        }

        /* Free the deleted block. */
        error = xfs_btree_free_block(cur, rbp);
        if (error)
                goto error0;

        /*
         * If we joined with the left neighbor, set the buffer in the
         * cursor to the left block, and fix up the index.
         */
        if (bp != lbp) {
                cur->bc_bufs[level] = lbp;
                cur->bc_ptrs[level] += lrecs;
                cur->bc_ra[level] = 0;
        }
        /*
         * If we joined with the right neighbor and there's a level above
         * us, increment the cursor at that level.
         */
        else if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) ||
                   (level + 1 < cur->bc_nlevels)) {
                error = xfs_btree_increment(cur, level + 1, &i);
                if (error)
                        goto error0;
        }

        /*
         * Readjust the ptr at this level if it's not a leaf, since it's
         * still pointing at the deletion point, which makes the cursor
         * inconsistent.  If this makes the ptr 0, the caller fixes it up.
         * We can't use decrement because it would change the next level up.
         */
        if (level > 0)
                cur->bc_ptrs[level]--;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        /* Return value means the next level up has something to do. */
        *stat = 2;
        return 0;

error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        if (tcur)
                xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Delete the record pointed to by cur.
 * The cursor refers to the place where the record was (could be inserted)
 * when the operation returns.
 */
int                                     /* error */
xfs_btree_delete(
        struct xfs_btree_cur    *cur,
        int                     *stat)  /* success/failure */
{
        int                     error;  /* error return value */
        int                     level;
        int                     i;

        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);

        /*
         * Go up the tree, starting at leaf level.
         *
         * If 2 is returned then a join was done; go to the next level.
         * Otherwise we are done.
         */
        for (level = 0, i = 2; i == 2; level++) {
                error = xfs_btree_delrec(cur, level, &i);
                if (error)
                        goto error0;
        }

        if (i == 0) {
                for (level = 1; level < cur->bc_nlevels; level++) {
                        if (cur->bc_ptrs[level] == 0) {
                                error = xfs_btree_decrement(cur, level, &i);
                                if (error)
                                        goto error0;
                                break;
                        }
                }
        }

        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = i;
        return 0;
error0:
        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
        return error;
}

/*
 * Get the data from the pointed-to record.
 */
int                                     /* error */
xfs_btree_get_rec(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        union xfs_btree_rec     **recp, /* output: btree record */
        int                     *stat)  /* output: success/failure */
{
        struct xfs_btree_block  *block; /* btree block */
        struct xfs_buf          *bp;    /* buffer pointer */
        int                     ptr;    /* record number */
#ifdef DEBUG
        int                     error;  /* error return value */
#endif

        ptr = cur->bc_ptrs[0];
        block = xfs_btree_get_block(cur, 0, &bp);

#ifdef DEBUG
        error = xfs_btree_check_block(cur, block, 0, bp);
        if (error)
                return error;
#endif

        /*
         * Off the right end or left end, return failure.
         */
        if (ptr > xfs_btree_get_numrecs(block) || ptr <= 0) {
                *stat = 0;
                return 0;
        }

        /*
         * Point to the record and extract its data.
         */
        *recp = xfs_btree_rec_addr(cur, ptr, block);
        *stat = 1;
        return 0;
}

/*
 * Change the owner of a btree.
 *
 * The mechanism we use here is ordered buffer logging. Because we don't know
 * how many buffers were are going to need to modify, we don't really want to
 * have to make transaction reservations for the worst case of every buffer in a
 * full size btree as that may be more space that we can fit in the log....
 *
 * We do the btree walk in the most optimal manner possible - we have sibling
 * pointers so we can just walk all the blocks on each level from left to right
 * in a single pass, and then move to the next level and do the same. We can
 * also do readahead on the sibling pointers to get IO moving more quickly,
 * though for slow disks this is unlikely to make much difference to performance
 * as the amount of CPU work we have to do before moving to the next block is
 * relatively small.
 *
 * For each btree block that we load, modify the owner appropriately, set the
 * buffer as an ordered buffer and log it appropriately. We need to ensure that
 * we mark the region we change dirty so that if the buffer is relogged in
 * a subsequent transaction the changes we make here as an ordered buffer are
 * correctly relogged in that transaction.  If we are in recovery context, then
 * just queue the modified buffer as delayed write buffer so the transaction
 * recovery completion writes the changes to disk.
 */
static int
xfs_btree_block_change_owner(
        struct xfs_btree_cur    *cur,
        int                     level,
        __uint64_t              new_owner,
        struct list_head        *buffer_list)
{
        struct xfs_btree_block  *block;
        struct xfs_buf          *bp;
        union xfs_btree_ptr     rptr;

        /* do right sibling readahead */
        xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);

        /* modify the owner */
        block = xfs_btree_get_block(cur, level, &bp);
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
                block->bb_u.l.bb_owner = cpu_to_be64(new_owner);
        else
                block->bb_u.s.bb_owner = cpu_to_be32(new_owner);

        /*
         * If the block is a root block hosted in an inode, we might not have a
         * buffer pointer here and we shouldn't attempt to log the change as the
         * information is already held in the inode and discarded when the root
         * block is formatted into the on-disk inode fork. We still change it,
         * though, so everything is consistent in memory.
         */
        if (bp) {
                if (cur->bc_tp) {
                        xfs_trans_ordered_buf(cur->bc_tp, bp);
                        xfs_btree_log_block(cur, bp, XFS_BB_OWNER);
                } else {
                        xfs_buf_delwri_queue(bp, buffer_list);
                }
        } else {
                ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);
                ASSERT(level == cur->bc_nlevels - 1);
        }

        /* now read rh sibling block for next iteration */
        xfs_btree_get_sibling(cur, block, &rptr, XFS_BB_RIGHTSIB);
        if (xfs_btree_ptr_is_null(cur, &rptr))
                return -ENOENT;

        return xfs_btree_lookup_get_block(cur, level, &rptr, &block);
}

int
xfs_btree_change_owner(
        struct xfs_btree_cur    *cur,
        __uint64_t              new_owner,
        struct list_head        *buffer_list)
{
        union xfs_btree_ptr     lptr;
        int                     level;
        struct xfs_btree_block  *block = NULL;
        int                     error = 0;

        cur->bc_ops->init_ptr_from_cur(cur, &lptr);

        /* for each level */
        for (level = cur->bc_nlevels - 1; level >= 0; level--) {
                /* grab the left hand block */
                error = xfs_btree_lookup_get_block(cur, level, &lptr, &block);
                if (error)
                        return error;

                /* readahead the left most block for the next level down */
                if (level > 0) {
                        union xfs_btree_ptr     *ptr;

                        ptr = xfs_btree_ptr_addr(cur, 1, block);
                        xfs_btree_readahead_ptr(cur, ptr, 1);

                        /* save for the next iteration of the loop */
                        lptr = *ptr;
                }

                /* for each buffer in the level */
                do {
                        error = xfs_btree_block_change_owner(cur, level,
                                                             new_owner,
                                                             buffer_list);
                } while (!error);

                if (error != -ENOENT)
                        return error;
        }

        return 0;
}

/**
 * xfs_btree_sblock_v5hdr_verify() -- verify the v5 fields of a short-format
 *                                    btree block
 *
 * @bp: buffer containing the btree block
 * @max_recs: pointer to the m_*_mxr max records field in the xfs mount
 * @pag_max_level: pointer to the per-ag max level field
 */
bool
xfs_btree_sblock_v5hdr_verify(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_perag        *pag = bp->b_pag;

        if (!xfs_sb_version_hascrc(&mp->m_sb))
                return false;
        if (!uuid_equal(&block->bb_u.s.bb_uuid, &mp->m_sb.sb_meta_uuid))
                return false;
        if (block->bb_u.s.bb_blkno != cpu_to_be64(bp->b_bn))
                return false;
        if (pag && be32_to_cpu(block->bb_u.s.bb_owner) != pag->pag_agno)
                return false;
        return true;
}

/**
 * xfs_btree_sblock_verify() -- verify a short-format btree block
 *
 * @bp: buffer containing the btree block
 * @max_recs: maximum records allowed in this btree node
 */
bool
xfs_btree_sblock_verify(
        struct xfs_buf          *bp,
        unsigned int            max_recs)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);

        /* numrecs verification */
        if (be16_to_cpu(block->bb_numrecs) > max_recs)
                return false;

        /* sibling pointer verification */
        if (!block->bb_u.s.bb_leftsib ||
            (be32_to_cpu(block->bb_u.s.bb_leftsib) >= mp->m_sb.sb_agblocks &&
             block->bb_u.s.bb_leftsib != cpu_to_be32(NULLAGBLOCK)))
                return false;
        if (!block->bb_u.s.bb_rightsib ||
            (be32_to_cpu(block->bb_u.s.bb_rightsib) >= mp->m_sb.sb_agblocks &&
             block->bb_u.s.bb_rightsib != cpu_to_be32(NULLAGBLOCK)))
                return false;

        return true;
}

/*
 * Calculate the number of btree levels needed to store a given number of
 * records in a short-format btree.
 */
uint
xfs_btree_compute_maxlevels(
        struct xfs_mount        *mp,
        uint                    *limits,
        unsigned long           len)
{
        uint                    level;
        unsigned long           maxblocks;

        maxblocks = (len + limits[0] - 1) / limits[0];
        for (level = 1; maxblocks > 1; level++)
                maxblocks = (maxblocks + limits[1] - 1) / limits[1];
        return level;
}