[XFS] add get_maxrecs btree operation

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / xfs / 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_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_error.h"

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

/*
 * Btree magic numbers.
 */
const __uint32_t xfs_magics[XFS_BTNUM_MAX] = {
        XFS_ABTB_MAGIC, XFS_ABTC_MAGIC, XFS_BMAP_MAGIC, XFS_IBT_MAGIC
};

/*
 * External routines.
 */

#ifdef DEBUG
/*
 * Debug routine: check that keys are in the right order.
 */
void
xfs_btree_check_key(
        xfs_btnum_t     btnum,          /* btree identifier */
        void            *ak1,           /* pointer to left (lower) key */
        void            *ak2)           /* pointer to right (higher) key */
{
        switch (btnum) {
        case XFS_BTNUM_BNO: {
                xfs_alloc_key_t *k1;
                xfs_alloc_key_t *k2;

                k1 = ak1;
                k2 = ak2;
                ASSERT(be32_to_cpu(k1->ar_startblock) < be32_to_cpu(k2->ar_startblock));
                break;
            }
        case XFS_BTNUM_CNT: {
                xfs_alloc_key_t *k1;
                xfs_alloc_key_t *k2;

                k1 = ak1;
                k2 = ak2;
                ASSERT(be32_to_cpu(k1->ar_blockcount) < be32_to_cpu(k2->ar_blockcount) ||
                       (k1->ar_blockcount == k2->ar_blockcount &&
                        be32_to_cpu(k1->ar_startblock) < be32_to_cpu(k2->ar_startblock)));
                break;
            }
        case XFS_BTNUM_BMAP: {
                xfs_bmbt_key_t  *k1;
                xfs_bmbt_key_t  *k2;

                k1 = ak1;
                k2 = ak2;
                ASSERT(be64_to_cpu(k1->br_startoff) < be64_to_cpu(k2->br_startoff));
                break;
            }
        case XFS_BTNUM_INO: {
                xfs_inobt_key_t *k1;
                xfs_inobt_key_t *k2;

                k1 = ak1;
                k2 = ak2;
                ASSERT(be32_to_cpu(k1->ir_startino) < be32_to_cpu(k2->ir_startino));
                break;
            }
        default:
                ASSERT(0);
        }
}

/*
 * Debug routine: check that records are in the right order.
 */
void
xfs_btree_check_rec(
        xfs_btnum_t     btnum,          /* btree identifier */
        void            *ar1,           /* pointer to left (lower) record */
        void            *ar2)           /* pointer to right (higher) record */
{
        switch (btnum) {
        case XFS_BTNUM_BNO: {
                xfs_alloc_rec_t *r1;
                xfs_alloc_rec_t *r2;

                r1 = ar1;
                r2 = ar2;
                ASSERT(be32_to_cpu(r1->ar_startblock) +
                       be32_to_cpu(r1->ar_blockcount) <=
                       be32_to_cpu(r2->ar_startblock));
                break;
            }
        case XFS_BTNUM_CNT: {
                xfs_alloc_rec_t *r1;
                xfs_alloc_rec_t *r2;

                r1 = ar1;
                r2 = ar2;
                ASSERT(be32_to_cpu(r1->ar_blockcount) < be32_to_cpu(r2->ar_blockcount) ||
                       (r1->ar_blockcount == r2->ar_blockcount &&
                        be32_to_cpu(r1->ar_startblock) < be32_to_cpu(r2->ar_startblock)));
                break;
            }
        case XFS_BTNUM_BMAP: {
                xfs_bmbt_rec_t  *r1;
                xfs_bmbt_rec_t  *r2;

                r1 = ar1;
                r2 = ar2;
                ASSERT(xfs_bmbt_disk_get_startoff(r1) +
                       xfs_bmbt_disk_get_blockcount(r1) <=
                       xfs_bmbt_disk_get_startoff(r2));
                break;
            }
        case XFS_BTNUM_INO: {
                xfs_inobt_rec_t *r1;
                xfs_inobt_rec_t *r2;

                r1 = ar1;
                r2 = ar2;
                ASSERT(be32_to_cpu(r1->ir_startino) + XFS_INODES_PER_CHUNK <=
                       be32_to_cpu(r2->ir_startino));
                break;
            }
        default:
                ASSERT(0);
        }
}
#endif  /* DEBUG */

int                                     /* error (0 or EFSCORRUPTED) */
xfs_btree_check_lblock(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_btree_lblock *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; /* block passes checks */
        struct xfs_mount        *mp;    /* file system mount point */

        mp = cur->bc_mp;
        lblock_ok =
                be32_to_cpu(block->bb_magic) == xfs_magics[cur->bc_btnum] &&
                be16_to_cpu(block->bb_level) == level &&
                be16_to_cpu(block->bb_numrecs) <=
                        cur->bc_ops->get_maxrecs(cur, level) &&
                block->bb_leftsib &&
                (be64_to_cpu(block->bb_leftsib) == NULLDFSBNO ||
                 XFS_FSB_SANITY_CHECK(mp, be64_to_cpu(block->bb_leftsib))) &&
                block->bb_rightsib &&
                (be64_to_cpu(block->bb_rightsib) == NULLDFSBNO ||
                 XFS_FSB_SANITY_CHECK(mp, be64_to_cpu(block->bb_rightsib)));
        if (unlikely(XFS_TEST_ERROR(!lblock_ok, mp,
                        XFS_ERRTAG_BTREE_CHECK_LBLOCK,
                        XFS_RANDOM_BTREE_CHECK_LBLOCK))) {
                if (bp)
                        xfs_buftrace("LBTREE ERROR", bp);
                XFS_ERROR_REPORT("xfs_btree_check_lblock", XFS_ERRLEVEL_LOW,
                                 mp);
                return XFS_ERROR(EFSCORRUPTED);
        }
        return 0;
}

int                                     /* error (0 or EFSCORRUPTED) */
xfs_btree_check_sblock(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        struct xfs_btree_sblock *block, /* btree short form block pointer */
        int                     level,  /* level of the btree block */
        struct xfs_buf          *bp)    /* buffer containing block */
{
        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; /* block passes checks */

        agbp = cur->bc_private.a.agbp;
        agf = XFS_BUF_TO_AGF(agbp);
        agflen = be32_to_cpu(agf->agf_length);
        sblock_ok =
                be32_to_cpu(block->bb_magic) == xfs_magics[cur->bc_btnum] &&
                be16_to_cpu(block->bb_level) == level &&
                be16_to_cpu(block->bb_numrecs) <=
                        cur->bc_ops->get_maxrecs(cur, level) &&
                (be32_to_cpu(block->bb_leftsib) == NULLAGBLOCK ||
                 be32_to_cpu(block->bb_leftsib) < agflen) &&
                block->bb_leftsib &&
                (be32_to_cpu(block->bb_rightsib) == NULLAGBLOCK ||
                 be32_to_cpu(block->bb_rightsib) < agflen) &&
                block->bb_rightsib;
        if (unlikely(XFS_TEST_ERROR(!sblock_ok, cur->bc_mp,
                        XFS_ERRTAG_BTREE_CHECK_SBLOCK,
                        XFS_RANDOM_BTREE_CHECK_SBLOCK))) {
                if (bp)
                        xfs_buftrace("SBTREE ERROR", bp);
                XFS_ERROR_REPORT("xfs_btree_check_sblock", XFS_ERRLEVEL_LOW,
                                 cur->bc_mp);
                return XFS_ERROR(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,
                                (struct xfs_btree_lblock *)block, level, bp);
        } else {
                return xfs_btree_check_sblock(cur,
                                (struct xfs_btree_sblock *)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_dfsbno_t            bno,    /* btree block disk address */
        int                     level)  /* btree block level */
{
        XFS_WANT_CORRUPTED_RETURN(
                level > 0 &&
                bno != NULLDFSBNO &&
                XFS_FSB_SANITY_CHECK(cur->bc_mp, bno));
        return 0;
}

/*
 * Check that (short) pointer is ok.
 */
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(
                level > 0 &&
                bno != NULLAGBLOCK &&
                bno != 0 &&
                bno < agblocks);
        return 0;
}

/*
 * Check that block ptr is ok.
 */
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);
        }
}

/*
 * 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_btree_setbuf(cur, i, NULL);
                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];
                if ((bp = cur->bc_bufs[i])) {
                        if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                                XFS_BUF_ADDR(bp), mp->m_bsize, 0, &bp))) {
                                xfs_btree_del_cursor(new, error);
                                *ncur = NULL;
                                return error;
                        }
                        new->bc_bufs[i] = bp;
                        ASSERT(bp);
                        ASSERT(!XFS_BUF_GETERROR(bp));
                } else
                        new->bc_bufs[i] = NULL;
        }
        *ncur = new;
        return 0;
}

/*
 * Get a 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_buf_t       *bp;            /* buffer pointer (return value) */
        xfs_daddr_t             d;              /* real disk block address */

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

/*
 * 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_buf_t       *bp;            /* buffer pointer (return value) */
        xfs_daddr_t             d;              /* real disk block address */

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

/*
 * 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 */
{
        xfs_btree_block_t       *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 be64_to_cpu(block->bb_u.l.bb_rightsib) == NULLDFSBNO;
        else
                return be32_to_cpu(block->bb_u.s.bb_rightsib) == NULLAGBLOCK;
}

/*
 * Change the cursor to point to the first record at the given level.
 * Other levels are unaffected.
 */
int                                     /* success=1, failure=0 */
xfs_btree_firstrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level)  /* level to change */
{
        xfs_btree_block_t       *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.
 */
int                                     /* success=1, failure=0 */
xfs_btree_lastrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level)  /* level to change */
{
        xfs_btree_block_t       *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                                     /* error */
xfs_btree_read_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 read_buf */
        xfs_buf_t       **bpp,          /* buffer for fsbno */
        int             refval)         /* ref count value for buffer */
{
        xfs_buf_t       *bp;            /* return value */
        xfs_daddr_t             d;              /* real disk block address */
        int             error;

        ASSERT(fsbno != NULLFSBLOCK);
        d = XFS_FSB_TO_DADDR(mp, fsbno);
        if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
                        mp->m_bsize, lock, &bp))) {
                return error;
        }
        ASSERT(!bp || !XFS_BUF_GETERROR(bp));
        if (bp != NULL) {
                XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, refval);
        }
        *bpp = bp;
        return 0;
}

/*
 * Get a buffer for the block, return it read in.
 * Short-form addressing.
 */
int                                     /* error */
xfs_btree_read_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 read_buf */
        xfs_buf_t       **bpp,          /* buffer for agno/agbno */
        int             refval)         /* ref count value for buffer */
{
        xfs_buf_t       *bp;            /* return value */
        xfs_daddr_t     d;              /* real disk block address */
        int             error;

        ASSERT(agno != NULLAGNUMBER);
        ASSERT(agbno != NULLAGBLOCK);
        d = XFS_AGB_TO_DADDR(mp, agno, agbno);
        if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
                                        mp->m_bsize, lock, &bp))) {
                return error;
        }
        ASSERT(!bp || !XFS_BUF_GETERROR(bp));
        if (bp != NULL) {
                switch (refval) {
                case XFS_ALLOC_BTREE_REF:
                        XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, refval);
                        break;
                case XFS_INO_BTREE_REF:
                        XFS_BUF_SET_VTYPE_REF(bp, B_FS_INOMAP, refval);
                        break;
                }
        }
        *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(
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_fsblock_t   fsbno,          /* file system block number */
        xfs_extlen_t    count)          /* count of filesystem blocks */
{
        xfs_daddr_t             d;

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

/*
 * Read-ahead the block, don't wait for it, don't return a buffer.
 * Short-form addressing.
 */
/* ARGSUSED */
void
xfs_btree_reada_bufs(
        xfs_mount_t     *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 */
{
        xfs_daddr_t             d;

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

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 != NULLDFSBNO) {
                xfs_btree_reada_bufl(cur->bc_mp, left, 1);
                rval++;
        }

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

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

        return rval;
}

/*
 * Read-ahead btree blocks, at the given level.
 * Bits in lr are set from XFS_BTCUR_{LEFT,RIGHT}RA.
 */
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);
}

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

        obp = cur->bc_bufs[lev];
        if (obp)
                xfs_trans_brelse(cur->bc_tp, obp);
        cur->bc_bufs[lev] = bp;
        cur->bc_ra[lev] = 0;
        if (!bp)
                return;
        b = XFS_BUF_TO_BLOCK(bp);
        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
                if (be64_to_cpu(b->bb_u.l.bb_leftsib) == NULLDFSBNO)
                        cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
                if (be64_to_cpu(b->bb_u.l.bb_rightsib) == NULLDFSBNO)
                        cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
        } else {
                if (be32_to_cpu(b->bb_u.s.bb_leftsib) == NULLAGBLOCK)
                        cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
                if (be32_to_cpu(b->bb_u.s.bb_rightsib) == NULLAGBLOCK)
                        cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
        }
}