xfs_bmap_btree.c

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/*
 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_itable.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_quota.h"

/*
 * Determine the extent state.
 */
/* ARGSUSED */
STATIC xfs_exntst_t
xfs_extent_state(
    xfs_filblks_t       blks,
    int         extent_flag)
{
    if (extent_flag) {
        ASSERT(blks != 0);  /* saved for DMIG */
        return XFS_EXT_UNWRITTEN;
    }
    return XFS_EXT_NORM;
}

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

    rblock->bb_magic = cpu_to_be32(XFS_BMAP_MAGIC);
    rblock->bb_level = dblock->bb_level;
    ASSERT(be16_to_cpu(rblock->bb_level) > 0);
    rblock->bb_numrecs = dblock->bb_numrecs;
    rblock->bb_u.l.bb_leftsib = cpu_to_be64(NULLDFSBNO);
    rblock->bb_u.l.bb_rightsib = cpu_to_be64(NULLDFSBNO);
    dmxr = xfs_bmdr_maxrecs(mp, dblocklen, 0);
    fkp = XFS_BMDR_KEY_ADDR(dblock, 1);
    tkp = XFS_BMBT_KEY_ADDR(mp, rblock, 1);
    fpp = XFS_BMDR_PTR_ADDR(dblock, 1, dmxr);
    tpp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, rblocklen);
    dmxr = be16_to_cpu(dblock->bb_numrecs);
    memcpy(tkp, fkp, sizeof(*fkp) * dmxr);
    memcpy(tpp, fpp, sizeof(*fpp) * dmxr);
}

/*
 * Convert a compressed bmap extent record to an uncompressed form.
 * This code must be in sync with the routines xfs_bmbt_get_startoff,
 * xfs_bmbt_get_startblock, xfs_bmbt_get_blockcount and xfs_bmbt_get_state.
 */
STATIC void
__xfs_bmbt_get_all(
        __uint64_t l0,
        __uint64_t l1,
        xfs_bmbt_irec_t *s)
{
    int ext_flag;
    xfs_exntst_t st;

    ext_flag = (int)(l0 >> (64 - BMBT_EXNTFLAG_BITLEN));
    s->br_startoff = ((xfs_fileoff_t)l0 &
               xfs_mask64lo(64 - BMBT_EXNTFLAG_BITLEN)) >> 9;
#if XFS_BIG_BLKNOS
    s->br_startblock = (((xfs_fsblock_t)l0 & xfs_mask64lo(9)) << 43) |
               (((xfs_fsblock_t)l1) >> 21);
#else
#ifdef DEBUG
    {
        xfs_dfsbno_t    b;

        b = (((xfs_dfsbno_t)l0 & xfs_mask64lo(9)) << 43) |
            (((xfs_dfsbno_t)l1) >> 21);
        ASSERT((b >> 32) == 0 || isnulldstartblock(b));
        s->br_startblock = (xfs_fsblock_t)b;
    }
#else   /* !DEBUG */
    s->br_startblock = (xfs_fsblock_t)(((xfs_dfsbno_t)l1) >> 21);
#endif  /* DEBUG */
#endif  /* XFS_BIG_BLKNOS */
    s->br_blockcount = (xfs_filblks_t)(l1 & xfs_mask64lo(21));
    /* This is xfs_extent_state() in-line */
    if (ext_flag) {
        ASSERT(s->br_blockcount != 0);  /* saved for DMIG */
        st = XFS_EXT_UNWRITTEN;
    } else
        st = XFS_EXT_NORM;
    s->br_state = st;
}

void
xfs_bmbt_get_all(
    xfs_bmbt_rec_host_t *r,
    xfs_bmbt_irec_t *s)
{
    __xfs_bmbt_get_all(r->l0, r->l1, s);
}

/*
 * Extract the blockcount field from an in memory bmap extent record.
 */
xfs_filblks_t
xfs_bmbt_get_blockcount(
    xfs_bmbt_rec_host_t *r)
{
    return (xfs_filblks_t)(r->l1 & xfs_mask64lo(21));
}

/*
 * Extract the startblock field from an in memory bmap extent record.
 */
xfs_fsblock_t
xfs_bmbt_get_startblock(
    xfs_bmbt_rec_host_t *r)
{
#if XFS_BIG_BLKNOS
    return (((xfs_fsblock_t)r->l0 & xfs_mask64lo(9)) << 43) |
           (((xfs_fsblock_t)r->l1) >> 21);
#else
#ifdef DEBUG
    xfs_dfsbno_t    b;

    b = (((xfs_dfsbno_t)r->l0 & xfs_mask64lo(9)) << 43) |
        (((xfs_dfsbno_t)r->l1) >> 21);
    ASSERT((b >> 32) == 0 || isnulldstartblock(b));
    return (xfs_fsblock_t)b;
#else   /* !DEBUG */
    return (xfs_fsblock_t)(((xfs_dfsbno_t)r->l1) >> 21);
#endif  /* DEBUG */
#endif  /* XFS_BIG_BLKNOS */
}

/*
 * Extract the startoff field from an in memory bmap extent record.
 */
xfs_fileoff_t
xfs_bmbt_get_startoff(
    xfs_bmbt_rec_host_t *r)
{
    return ((xfs_fileoff_t)r->l0 &
         xfs_mask64lo(64 - BMBT_EXNTFLAG_BITLEN)) >> 9;
}

xfs_exntst_t
xfs_bmbt_get_state(
    xfs_bmbt_rec_host_t *r)
{
    int ext_flag;

    ext_flag = (int)((r->l0) >> (64 - BMBT_EXNTFLAG_BITLEN));
    return xfs_extent_state(xfs_bmbt_get_blockcount(r),
                ext_flag);
}

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

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


/*
 * Set all the fields in a bmap extent record from the arguments.
 */
void
xfs_bmbt_set_allf(
    xfs_bmbt_rec_host_t *r,
    xfs_fileoff_t       startoff,
    xfs_fsblock_t       startblock,
    xfs_filblks_t       blockcount,
    xfs_exntst_t        state)
{
    int     extent_flag = (state == XFS_EXT_NORM) ? 0 : 1;

    ASSERT(state == XFS_EXT_NORM || state == XFS_EXT_UNWRITTEN);
    ASSERT((startoff & xfs_mask64hi(64-BMBT_STARTOFF_BITLEN)) == 0);
    ASSERT((blockcount & xfs_mask64hi(64-BMBT_BLOCKCOUNT_BITLEN)) == 0);

#if XFS_BIG_BLKNOS
    ASSERT((startblock & xfs_mask64hi(64-BMBT_STARTBLOCK_BITLEN)) == 0);

    r->l0 = ((xfs_bmbt_rec_base_t)extent_flag << 63) |
        ((xfs_bmbt_rec_base_t)startoff << 9) |
        ((xfs_bmbt_rec_base_t)startblock >> 43);
    r->l1 = ((xfs_bmbt_rec_base_t)startblock << 21) |
        ((xfs_bmbt_rec_base_t)blockcount &
        (xfs_bmbt_rec_base_t)xfs_mask64lo(21));
#else   /* !XFS_BIG_BLKNOS */
    if (isnullstartblock(startblock)) {
        r->l0 = ((xfs_bmbt_rec_base_t)extent_flag << 63) |
            ((xfs_bmbt_rec_base_t)startoff << 9) |
             (xfs_bmbt_rec_base_t)xfs_mask64lo(9);
        r->l1 = xfs_mask64hi(11) |
              ((xfs_bmbt_rec_base_t)startblock << 21) |
              ((xfs_bmbt_rec_base_t)blockcount &
               (xfs_bmbt_rec_base_t)xfs_mask64lo(21));
    } else {
        r->l0 = ((xfs_bmbt_rec_base_t)extent_flag << 63) |
            ((xfs_bmbt_rec_base_t)startoff << 9);
        r->l1 = ((xfs_bmbt_rec_base_t)startblock << 21) |
             ((xfs_bmbt_rec_base_t)blockcount &
             (xfs_bmbt_rec_base_t)xfs_mask64lo(21));
    }
#endif  /* XFS_BIG_BLKNOS */
}

/*
 * Set all the fields in a bmap extent record from the uncompressed form.
 */
void
xfs_bmbt_set_all(
    xfs_bmbt_rec_host_t *r,
    xfs_bmbt_irec_t *s)
{
    xfs_bmbt_set_allf(r, s->br_startoff, s->br_startblock,
                 s->br_blockcount, s->br_state);
}


/*
 * Set all the fields in a disk format bmap extent record from the arguments.
 */
void
xfs_bmbt_disk_set_allf(
    xfs_bmbt_rec_t      *r,
    xfs_fileoff_t       startoff,
    xfs_fsblock_t       startblock,
    xfs_filblks_t       blockcount,
    xfs_exntst_t        state)
{
    int         extent_flag = (state == XFS_EXT_NORM) ? 0 : 1;

    ASSERT(state == XFS_EXT_NORM || state == XFS_EXT_UNWRITTEN);
    ASSERT((startoff & xfs_mask64hi(64-BMBT_STARTOFF_BITLEN)) == 0);
    ASSERT((blockcount & xfs_mask64hi(64-BMBT_BLOCKCOUNT_BITLEN)) == 0);

#if XFS_BIG_BLKNOS
    ASSERT((startblock & xfs_mask64hi(64-BMBT_STARTBLOCK_BITLEN)) == 0);

    r->l0 = cpu_to_be64(
        ((xfs_bmbt_rec_base_t)extent_flag << 63) |
         ((xfs_bmbt_rec_base_t)startoff << 9) |
         ((xfs_bmbt_rec_base_t)startblock >> 43));
    r->l1 = cpu_to_be64(
        ((xfs_bmbt_rec_base_t)startblock << 21) |
         ((xfs_bmbt_rec_base_t)blockcount &
          (xfs_bmbt_rec_base_t)xfs_mask64lo(21)));
#else   /* !XFS_BIG_BLKNOS */
    if (isnullstartblock(startblock)) {
        r->l0 = cpu_to_be64(
            ((xfs_bmbt_rec_base_t)extent_flag << 63) |
             ((xfs_bmbt_rec_base_t)startoff << 9) |
              (xfs_bmbt_rec_base_t)xfs_mask64lo(9));
        r->l1 = cpu_to_be64(xfs_mask64hi(11) |
              ((xfs_bmbt_rec_base_t)startblock << 21) |
              ((xfs_bmbt_rec_base_t)blockcount &
               (xfs_bmbt_rec_base_t)xfs_mask64lo(21)));
    } else {
        r->l0 = cpu_to_be64(
            ((xfs_bmbt_rec_base_t)extent_flag << 63) |
             ((xfs_bmbt_rec_base_t)startoff << 9));
        r->l1 = cpu_to_be64(
            ((xfs_bmbt_rec_base_t)startblock << 21) |
             ((xfs_bmbt_rec_base_t)blockcount &
              (xfs_bmbt_rec_base_t)xfs_mask64lo(21)));
    }
#endif  /* XFS_BIG_BLKNOS */
}

/*
 * Set all the fields in a bmap extent record from the uncompressed form.
 */
STATIC void
xfs_bmbt_disk_set_all(
    xfs_bmbt_rec_t  *r,
    xfs_bmbt_irec_t *s)
{
    xfs_bmbt_disk_set_allf(r, s->br_startoff, s->br_startblock,
                  s->br_blockcount, s->br_state);
}

/*
 * Set the blockcount field in a bmap extent record.
 */
void
xfs_bmbt_set_blockcount(
    xfs_bmbt_rec_host_t *r,
    xfs_filblks_t   v)
{
    ASSERT((v & xfs_mask64hi(43)) == 0);
    r->l1 = (r->l1 & (xfs_bmbt_rec_base_t)xfs_mask64hi(43)) |
          (xfs_bmbt_rec_base_t)(v & xfs_mask64lo(21));
}

/*
 * Set the startblock field in a bmap extent record.
 */
void
xfs_bmbt_set_startblock(
    xfs_bmbt_rec_host_t *r,
    xfs_fsblock_t   v)
{
#if XFS_BIG_BLKNOS
    ASSERT((v & xfs_mask64hi(12)) == 0);
    r->l0 = (r->l0 & (xfs_bmbt_rec_base_t)xfs_mask64hi(55)) |
          (xfs_bmbt_rec_base_t)(v >> 43);
    r->l1 = (r->l1 & (xfs_bmbt_rec_base_t)xfs_mask64lo(21)) |
          (xfs_bmbt_rec_base_t)(v << 21);
#else   /* !XFS_BIG_BLKNOS */
    if (isnullstartblock(v)) {
        r->l0 |= (xfs_bmbt_rec_base_t)xfs_mask64lo(9);
        r->l1 = (xfs_bmbt_rec_base_t)xfs_mask64hi(11) |
              ((xfs_bmbt_rec_base_t)v << 21) |
              (r->l1 & (xfs_bmbt_rec_base_t)xfs_mask64lo(21));
    } else {
        r->l0 &= ~(xfs_bmbt_rec_base_t)xfs_mask64lo(9);
        r->l1 = ((xfs_bmbt_rec_base_t)v << 21) |
              (r->l1 & (xfs_bmbt_rec_base_t)xfs_mask64lo(21));
    }
#endif  /* XFS_BIG_BLKNOS */
}

/*
 * Set the startoff field in a bmap extent record.
 */
void
xfs_bmbt_set_startoff(
    xfs_bmbt_rec_host_t *r,
    xfs_fileoff_t   v)
{
    ASSERT((v & xfs_mask64hi(9)) == 0);
    r->l0 = (r->l0 & (xfs_bmbt_rec_base_t) xfs_mask64hi(1)) |
        ((xfs_bmbt_rec_base_t)v << 9) |
          (r->l0 & (xfs_bmbt_rec_base_t)xfs_mask64lo(9));
}

/*
 * Set the extent state field in a bmap extent record.
 */
void
xfs_bmbt_set_state(
    xfs_bmbt_rec_host_t *r,
    xfs_exntst_t    v)
{
    ASSERT(v == XFS_EXT_NORM || v == XFS_EXT_UNWRITTEN);
    if (v == XFS_EXT_NORM)
        r->l0 &= xfs_mask64lo(64 - BMBT_EXNTFLAG_BITLEN);
    else
        r->l0 |= xfs_mask64hi(BMBT_EXNTFLAG_BITLEN);
}

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

    ASSERT(rblock->bb_magic == cpu_to_be32(XFS_BMAP_MAGIC));
    ASSERT(rblock->bb_u.l.bb_leftsib == cpu_to_be64(NULLDFSBNO));
    ASSERT(rblock->bb_u.l.bb_rightsib == cpu_to_be64(NULLDFSBNO));
    ASSERT(rblock->bb_level != 0);
    dblock->bb_level = rblock->bb_level;
    dblock->bb_numrecs = rblock->bb_numrecs;
    dmxr = xfs_bmdr_maxrecs(mp, dblocklen, 0);
    fkp = XFS_BMBT_KEY_ADDR(mp, rblock, 1);
    tkp = XFS_BMDR_KEY_ADDR(dblock, 1);
    fpp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, rblocklen);
    tpp = XFS_BMDR_PTR_ADDR(dblock, 1, dmxr);
    dmxr = be16_to_cpu(dblock->bb_numrecs);
    memcpy(tkp, fkp, sizeof(*fkp) * dmxr);
    memcpy(tpp, fpp, sizeof(*fpp) * dmxr);
}

/*
 * Check extent records, which have just been read, for
 * any bit in the extent flag field. ASSERT on debug
 * kernels, as this condition should not occur.
 * Return an error condition (1) if any flags found,
 * otherwise return 0.
 */

int
xfs_check_nostate_extents(
    xfs_ifork_t     *ifp,
    xfs_extnum_t        idx,
    xfs_extnum_t        num)
{
    for (; num > 0; num--, idx++) {
        xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, idx);
        if ((ep->l0 >>
             (64 - BMBT_EXNTFLAG_BITLEN)) != 0) {
            ASSERT(0);
            return 1;
        }
    }
    return 0;
}


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

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

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

    return new;
}

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

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

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

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

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

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

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

    if (args.fsbno == NULLFSBLOCK && args.minleft) {
        /*
         * Could not find an AG with enough free space to satisfy
         * a full btree split.  Try again without minleft and if
         * successful activate the lowspace algorithm.
         */
        args.fsbno = 0;
        args.type = XFS_ALLOCTYPE_FIRST_AG;
        args.minleft = 0;
        error = xfs_alloc_vextent(&args);
        if (error)
            goto error0;
        cur->bc_private.b.flist->xbf_low = 1;
    }
    if (args.fsbno == NULLFSBLOCK) {
        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
        *stat = 0;
        return 0;
    }
    ASSERT(args.len == 1);
    cur->bc_private.b.firstblock = args.fsbno;
    cur->bc_private.b.allocated++;
    cur->bc_private.b.ip->i_d.di_nblocks++;
    xfs_trans_log_inode(args.tp, cur->bc_private.b.ip, XFS_ILOG_CORE);
    xfs_trans_mod_dquot_byino(args.tp, cur->bc_private.b.ip,
            XFS_TRANS_DQ_BCOUNT, 1L);

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

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

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

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

    xfs_bmap_add_free(fsbno, 1, cur->bc_private.b.flist, mp);
    ip->i_d.di_nblocks--;

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

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

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

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

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

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

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

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

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

}

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

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

STATIC void
xfs_bmbt_init_rec_from_key(
    union xfs_btree_key *key,
    union xfs_btree_rec *rec)
{
    ASSERT(key->bmbt.br_startoff != 0);

    xfs_bmbt_disk_set_allf(&rec->bmbt, be64_to_cpu(key->bmbt.br_startoff),
                   0, 0, XFS_EXT_NORM);
}

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

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

STATIC __int64_t
xfs_bmbt_key_diff(
    struct xfs_btree_cur    *cur,
    union xfs_btree_key *key)
{
    return (__int64_t)be64_to_cpu(key->bmbt.br_startoff) -
                      cur->bc_rec.b.br_startoff;
}

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

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

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

    .dup_cursor     = xfs_bmbt_dup_cursor,
    .update_cursor      = xfs_bmbt_update_cursor,
    .alloc_block        = xfs_bmbt_alloc_block,
    .free_block     = xfs_bmbt_free_block,
    .get_maxrecs        = xfs_bmbt_get_maxrecs,
    .get_minrecs        = xfs_bmbt_get_minrecs,
    .get_dmaxrecs       = xfs_bmbt_get_dmaxrecs,
    .init_key_from_rec  = xfs_bmbt_init_key_from_rec,
    .init_rec_from_key  = xfs_bmbt_init_rec_from_key,
    .init_rec_from_cur  = xfs_bmbt_init_rec_from_cur,
    .init_ptr_from_cur  = xfs_bmbt_init_ptr_from_cur,
    .key_diff       = xfs_bmbt_key_diff,
#ifdef DEBUG
    .keys_inorder       = xfs_bmbt_keys_inorder,
    .recs_inorder       = xfs_bmbt_recs_inorder,
#endif
};

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

    cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_SLEEP);

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

    cur->bc_ops = &xfs_bmbt_ops;
    cur->bc_flags = XFS_BTREE_LONG_PTRS | XFS_BTREE_ROOT_IN_INODE;

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

    return cur;
}

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

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

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

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