xfs_dir2_data.c

Go to the documentation of this file.

/*
 * 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_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_da_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_dir2_format.h"
#include "xfs_dir2_priv.h"
#include "xfs_error.h"

STATIC xfs_dir2_data_free_t *
xfs_dir2_data_freefind(xfs_dir2_data_hdr_t *hdr, xfs_dir2_data_unused_t *dup);

#ifdef DEBUG
/*
 * Check the consistency of the data block.
 * The input can also be a block-format directory.
 * Pop an assert if we find anything bad.
 */
void
xfs_dir2_data_check(
    struct xfs_inode    *dp,        /* incore inode pointer */
    struct xfs_buf      *bp)        /* data block's buffer */
{
    xfs_dir2_dataptr_t  addr;       /* addr for leaf lookup */
    xfs_dir2_data_free_t    *bf;        /* bestfree table */
    xfs_dir2_block_tail_t   *btp=NULL;  /* block tail */
    int         count;      /* count of entries found */
    xfs_dir2_data_hdr_t *hdr;       /* data block header */
    xfs_dir2_data_entry_t   *dep;       /* data entry */
    xfs_dir2_data_free_t    *dfp;       /* bestfree entry */
    xfs_dir2_data_unused_t  *dup;       /* unused entry */
    char            *endp;      /* end of useful data */
    int         freeseen;   /* mask of bestfrees seen */
    xfs_dahash_t        hash;       /* hash of current name */
    int         i;      /* leaf index */
    int         lastfree;   /* last entry was unused */
    xfs_dir2_leaf_entry_t   *lep=NULL;  /* block leaf entries */
    xfs_mount_t     *mp;        /* filesystem mount point */
    char            *p;     /* current data position */
    int         stale;      /* count of stale leaves */
    struct xfs_name     name;

    mp = dp->i_mount;
    hdr = bp->b_addr;
    bf = hdr->bestfree;
    p = (char *)(hdr + 1);

    if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
        btp = xfs_dir2_block_tail_p(mp, hdr);
        lep = xfs_dir2_block_leaf_p(btp);
        endp = (char *)lep;
    } else {
        ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC));
        endp = (char *)hdr + mp->m_dirblksize;
    }

    count = lastfree = freeseen = 0;
    /*
     * Account for zero bestfree entries.
     */
    if (!bf[0].length) {
        ASSERT(!bf[0].offset);
        freeseen |= 1 << 0;
    }
    if (!bf[1].length) {
        ASSERT(!bf[1].offset);
        freeseen |= 1 << 1;
    }
    if (!bf[2].length) {
        ASSERT(!bf[2].offset);
        freeseen |= 1 << 2;
    }
    ASSERT(be16_to_cpu(bf[0].length) >= be16_to_cpu(bf[1].length));
    ASSERT(be16_to_cpu(bf[1].length) >= be16_to_cpu(bf[2].length));
    /*
     * Loop over the data/unused entries.
     */
    while (p < endp) {
        dup = (xfs_dir2_data_unused_t *)p;
        /*
         * If it's unused, look for the space in the bestfree table.
         * If we find it, account for that, else make sure it
         * doesn't need to be there.
         */
        if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
            ASSERT(lastfree == 0);
            ASSERT(be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)) ==
                   (char *)dup - (char *)hdr);
            dfp = xfs_dir2_data_freefind(hdr, dup);
            if (dfp) {
                i = (int)(dfp - bf);
                ASSERT((freeseen & (1 << i)) == 0);
                freeseen |= 1 << i;
            } else {
                ASSERT(be16_to_cpu(dup->length) <=
                       be16_to_cpu(bf[2].length));
            }
            p += be16_to_cpu(dup->length);
            lastfree = 1;
            continue;
        }
        /*
         * It's a real entry.  Validate the fields.
         * If this is a block directory then make sure it's
         * in the leaf section of the block.
         * The linear search is crude but this is DEBUG code.
         */
        dep = (xfs_dir2_data_entry_t *)p;
        ASSERT(dep->namelen != 0);
        ASSERT(xfs_dir_ino_validate(mp, be64_to_cpu(dep->inumber)) == 0);
        ASSERT(be16_to_cpu(*xfs_dir2_data_entry_tag_p(dep)) ==
               (char *)dep - (char *)hdr);
        count++;
        lastfree = 0;
        if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
            addr = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
                (xfs_dir2_data_aoff_t)
                ((char *)dep - (char *)hdr));
            name.name = dep->name;
            name.len = dep->namelen;
            hash = mp->m_dirnameops->hashname(&name);
            for (i = 0; i < be32_to_cpu(btp->count); i++) {
                if (be32_to_cpu(lep[i].address) == addr &&
                    be32_to_cpu(lep[i].hashval) == hash)
                    break;
            }
            ASSERT(i < be32_to_cpu(btp->count));
        }
        p += xfs_dir2_data_entsize(dep->namelen);
    }
    /*
     * Need to have seen all the entries and all the bestfree slots.
     */
    ASSERT(freeseen == 7);
    if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
        for (i = stale = 0; i < be32_to_cpu(btp->count); i++) {
            if (lep[i].address ==
                cpu_to_be32(XFS_DIR2_NULL_DATAPTR))
                stale++;
            if (i > 0)
                ASSERT(be32_to_cpu(lep[i].hashval) >= be32_to_cpu(lep[i - 1].hashval));
        }
        ASSERT(count == be32_to_cpu(btp->count) - be32_to_cpu(btp->stale));
        ASSERT(stale == be32_to_cpu(btp->stale));
    }
}
#endif

/*
 * Given a data block and an unused entry from that block,
 * return the bestfree entry if any that corresponds to it.
 */
STATIC xfs_dir2_data_free_t *
xfs_dir2_data_freefind(
    xfs_dir2_data_hdr_t *hdr,       /* data block */
    xfs_dir2_data_unused_t  *dup)       /* data unused entry */
{
    xfs_dir2_data_free_t    *dfp;       /* bestfree entry */
    xfs_dir2_data_aoff_t    off;        /* offset value needed */
#if defined(DEBUG) && defined(__KERNEL__)
    int         matched;    /* matched the value */
    int         seenzero;   /* saw a 0 bestfree entry */
#endif

    off = (xfs_dir2_data_aoff_t)((char *)dup - (char *)hdr);
#if defined(DEBUG) && defined(__KERNEL__)
    /*
     * Validate some consistency in the bestfree table.
     * Check order, non-overlapping entries, and if we find the
     * one we're looking for it has to be exact.
     */
    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
    for (dfp = &hdr->bestfree[0], seenzero = matched = 0;
         dfp < &hdr->bestfree[XFS_DIR2_DATA_FD_COUNT];
         dfp++) {
        if (!dfp->offset) {
            ASSERT(!dfp->length);
            seenzero = 1;
            continue;
        }
        ASSERT(seenzero == 0);
        if (be16_to_cpu(dfp->offset) == off) {
            matched = 1;
            ASSERT(dfp->length == dup->length);
        } else if (off < be16_to_cpu(dfp->offset))
            ASSERT(off + be16_to_cpu(dup->length) <= be16_to_cpu(dfp->offset));
        else
            ASSERT(be16_to_cpu(dfp->offset) + be16_to_cpu(dfp->length) <= off);
        ASSERT(matched || be16_to_cpu(dfp->length) >= be16_to_cpu(dup->length));
        if (dfp > &hdr->bestfree[0])
            ASSERT(be16_to_cpu(dfp[-1].length) >= be16_to_cpu(dfp[0].length));
    }
#endif
    /*
     * If this is smaller than the smallest bestfree entry,
     * it can't be there since they're sorted.
     */
    if (be16_to_cpu(dup->length) <
        be16_to_cpu(hdr->bestfree[XFS_DIR2_DATA_FD_COUNT - 1].length))
        return NULL;
    /*
     * Look at the three bestfree entries for our guy.
     */
    for (dfp = &hdr->bestfree[0];
         dfp < &hdr->bestfree[XFS_DIR2_DATA_FD_COUNT];
         dfp++) {
        if (!dfp->offset)
            return NULL;
        if (be16_to_cpu(dfp->offset) == off)
            return dfp;
    }
    /*
     * Didn't find it.  This only happens if there are duplicate lengths.
     */
    return NULL;
}

/*
 * Insert an unused-space entry into the bestfree table.
 */
xfs_dir2_data_free_t *              /* entry inserted */
xfs_dir2_data_freeinsert(
    xfs_dir2_data_hdr_t *hdr,       /* data block pointer */
    xfs_dir2_data_unused_t  *dup,       /* unused space */
    int         *loghead)   /* log the data header (out) */
{
    xfs_dir2_data_free_t    *dfp;       /* bestfree table pointer */
    xfs_dir2_data_free_t    new;        /* new bestfree entry */

#ifdef __KERNEL__
    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
#endif
    dfp = hdr->bestfree;
    new.length = dup->length;
    new.offset = cpu_to_be16((char *)dup - (char *)hdr);

    /*
     * Insert at position 0, 1, or 2; or not at all.
     */
    if (be16_to_cpu(new.length) > be16_to_cpu(dfp[0].length)) {
        dfp[2] = dfp[1];
        dfp[1] = dfp[0];
        dfp[0] = new;
        *loghead = 1;
        return &dfp[0];
    }
    if (be16_to_cpu(new.length) > be16_to_cpu(dfp[1].length)) {
        dfp[2] = dfp[1];
        dfp[1] = new;
        *loghead = 1;
        return &dfp[1];
    }
    if (be16_to_cpu(new.length) > be16_to_cpu(dfp[2].length)) {
        dfp[2] = new;
        *loghead = 1;
        return &dfp[2];
    }
    return NULL;
}

/*
 * Remove a bestfree entry from the table.
 */
STATIC void
xfs_dir2_data_freeremove(
    xfs_dir2_data_hdr_t *hdr,       /* data block header */
    xfs_dir2_data_free_t    *dfp,       /* bestfree entry pointer */
    int         *loghead)   /* out: log data header */
{
#ifdef __KERNEL__
    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
#endif
    /*
     * It's the first entry, slide the next 2 up.
     */
    if (dfp == &hdr->bestfree[0]) {
        hdr->bestfree[0] = hdr->bestfree[1];
        hdr->bestfree[1] = hdr->bestfree[2];
    }
    /*
     * It's the second entry, slide the 3rd entry up.
     */
    else if (dfp == &hdr->bestfree[1])
        hdr->bestfree[1] = hdr->bestfree[2];
    /*
     * Must be the last entry.
     */
    else
        ASSERT(dfp == &hdr->bestfree[2]);
    /*
     * Clear the 3rd entry, must be zero now.
     */
    hdr->bestfree[2].length = 0;
    hdr->bestfree[2].offset = 0;
    *loghead = 1;
}

/*
 * Given a data block, reconstruct its bestfree map.
 */
void
xfs_dir2_data_freescan(
    xfs_mount_t     *mp,        /* filesystem mount point */
    xfs_dir2_data_hdr_t *hdr,       /* data block header */
    int         *loghead)   /* out: log data header */
{
    xfs_dir2_block_tail_t   *btp;       /* block tail */
    xfs_dir2_data_entry_t   *dep;       /* active data entry */
    xfs_dir2_data_unused_t  *dup;       /* unused data entry */
    char            *endp;      /* end of block's data */
    char            *p;     /* current entry pointer */

#ifdef __KERNEL__
    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
#endif
    /*
     * Start by clearing the table.
     */
    memset(hdr->bestfree, 0, sizeof(hdr->bestfree));
    *loghead = 1;
    /*
     * Set up pointers.
     */
    p = (char *)(hdr + 1);
    if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
        btp = xfs_dir2_block_tail_p(mp, hdr);
        endp = (char *)xfs_dir2_block_leaf_p(btp);
    } else
        endp = (char *)hdr + mp->m_dirblksize;
    /*
     * Loop over the block's entries.
     */
    while (p < endp) {
        dup = (xfs_dir2_data_unused_t *)p;
        /*
         * If it's a free entry, insert it.
         */
        if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
            ASSERT((char *)dup - (char *)hdr ==
                   be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)));
            xfs_dir2_data_freeinsert(hdr, dup, loghead);
            p += be16_to_cpu(dup->length);
        }
        /*
         * For active entries, check their tags and skip them.
         */
        else {
            dep = (xfs_dir2_data_entry_t *)p;
            ASSERT((char *)dep - (char *)hdr ==
                   be16_to_cpu(*xfs_dir2_data_entry_tag_p(dep)));
            p += xfs_dir2_data_entsize(dep->namelen);
        }
    }
}

/*
 * Initialize a data block at the given block number in the directory.
 * Give back the buffer for the created block.
 */
int                     /* error */
xfs_dir2_data_init(
    xfs_da_args_t       *args,      /* directory operation args */
    xfs_dir2_db_t       blkno,      /* logical dir block number */
    struct xfs_buf      **bpp)      /* output block buffer */
{
    struct xfs_buf      *bp;        /* block buffer */
    xfs_dir2_data_hdr_t *hdr;       /* data block header */
    xfs_inode_t     *dp;        /* incore directory inode */
    xfs_dir2_data_unused_t  *dup;       /* unused entry pointer */
    int         error;      /* error return value */
    int         i;      /* bestfree index */
    xfs_mount_t     *mp;        /* filesystem mount point */
    xfs_trans_t     *tp;        /* transaction pointer */
    int                     t;              /* temp */

    dp = args->dp;
    mp = dp->i_mount;
    tp = args->trans;
    /*
     * Get the buffer set up for the block.
     */
    error = xfs_da_get_buf(tp, dp, xfs_dir2_db_to_da(mp, blkno), -1, &bp,
        XFS_DATA_FORK);
    if (error) {
        return error;
    }
    ASSERT(bp != NULL);

    /*
     * Initialize the header.
     */
    hdr = bp->b_addr;
    hdr->magic = cpu_to_be32(XFS_DIR2_DATA_MAGIC);
    hdr->bestfree[0].offset = cpu_to_be16(sizeof(*hdr));
    for (i = 1; i < XFS_DIR2_DATA_FD_COUNT; i++) {
        hdr->bestfree[i].length = 0;
        hdr->bestfree[i].offset = 0;
    }

    /*
     * Set up an unused entry for the block's body.
     */
    dup = (xfs_dir2_data_unused_t *)(hdr + 1);
    dup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);

    t = mp->m_dirblksize - (uint)sizeof(*hdr);
    hdr->bestfree[0].length = cpu_to_be16(t);
    dup->length = cpu_to_be16(t);
    *xfs_dir2_data_unused_tag_p(dup) = cpu_to_be16((char *)dup - (char *)hdr);
    /*
     * Log it and return it.
     */
    xfs_dir2_data_log_header(tp, bp);
    xfs_dir2_data_log_unused(tp, bp, dup);
    *bpp = bp;
    return 0;
}

/*
 * Log an active data entry from the block.
 */
void
xfs_dir2_data_log_entry(
    struct xfs_trans    *tp,
    struct xfs_buf      *bp,
    xfs_dir2_data_entry_t   *dep)       /* data entry pointer */
{
    xfs_dir2_data_hdr_t *hdr = bp->b_addr;

    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));

    xfs_trans_log_buf(tp, bp, (uint)((char *)dep - (char *)hdr),
        (uint)((char *)(xfs_dir2_data_entry_tag_p(dep) + 1) -
               (char *)hdr - 1));
}

/*
 * Log a data block header.
 */
void
xfs_dir2_data_log_header(
    struct xfs_trans    *tp,
    struct xfs_buf      *bp)
{
    xfs_dir2_data_hdr_t *hdr = bp->b_addr;

    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));

    xfs_trans_log_buf(tp, bp, 0, sizeof(*hdr) - 1);
}

/*
 * Log a data unused entry.
 */
void
xfs_dir2_data_log_unused(
    struct xfs_trans    *tp,
    struct xfs_buf      *bp,
    xfs_dir2_data_unused_t  *dup)       /* data unused pointer */
{
    xfs_dir2_data_hdr_t *hdr = bp->b_addr;

    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));

    /*
     * Log the first part of the unused entry.
     */
    xfs_trans_log_buf(tp, bp, (uint)((char *)dup - (char *)hdr),
        (uint)((char *)&dup->length + sizeof(dup->length) -
               1 - (char *)hdr));
    /*
     * Log the end (tag) of the unused entry.
     */
    xfs_trans_log_buf(tp, bp,
        (uint)((char *)xfs_dir2_data_unused_tag_p(dup) - (char *)hdr),
        (uint)((char *)xfs_dir2_data_unused_tag_p(dup) - (char *)hdr +
               sizeof(xfs_dir2_data_off_t) - 1));
}

/*
 * Make a byte range in the data block unused.
 * Its current contents are unimportant.
 */
void
xfs_dir2_data_make_free(
    struct xfs_trans    *tp,
    struct xfs_buf      *bp,
    xfs_dir2_data_aoff_t    offset,     /* starting byte offset */
    xfs_dir2_data_aoff_t    len,        /* length in bytes */
    int         *needlogp,  /* out: log header */
    int         *needscanp) /* out: regen bestfree */
{
    xfs_dir2_data_hdr_t *hdr;       /* data block pointer */
    xfs_dir2_data_free_t    *dfp;       /* bestfree pointer */
    char            *endptr;    /* end of data area */
    xfs_mount_t     *mp;        /* filesystem mount point */
    int         needscan;   /* need to regen bestfree */
    xfs_dir2_data_unused_t  *newdup;    /* new unused entry */
    xfs_dir2_data_unused_t  *postdup;   /* unused entry after us */
    xfs_dir2_data_unused_t  *prevdup;   /* unused entry before us */

    mp = tp->t_mountp;
    hdr = bp->b_addr;

    /*
     * Figure out where the end of the data area is.
     */
    if (hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC))
        endptr = (char *)hdr + mp->m_dirblksize;
    else {
        xfs_dir2_block_tail_t   *btp;   /* block tail */

        ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
        btp = xfs_dir2_block_tail_p(mp, hdr);
        endptr = (char *)xfs_dir2_block_leaf_p(btp);
    }
    /*
     * If this isn't the start of the block, then back up to
     * the previous entry and see if it's free.
     */
    if (offset > sizeof(*hdr)) {
        __be16          *tagp;  /* tag just before us */

        tagp = (__be16 *)((char *)hdr + offset) - 1;
        prevdup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));
        if (be16_to_cpu(prevdup->freetag) != XFS_DIR2_DATA_FREE_TAG)
            prevdup = NULL;
    } else
        prevdup = NULL;
    /*
     * If this isn't the end of the block, see if the entry after
     * us is free.
     */
    if ((char *)hdr + offset + len < endptr) {
        postdup =
            (xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
        if (be16_to_cpu(postdup->freetag) != XFS_DIR2_DATA_FREE_TAG)
            postdup = NULL;
    } else
        postdup = NULL;
    ASSERT(*needscanp == 0);
    needscan = 0;
    /*
     * Previous and following entries are both free,
     * merge everything into a single free entry.
     */
    if (prevdup && postdup) {
        xfs_dir2_data_free_t    *dfp2;  /* another bestfree pointer */

        /*
         * See if prevdup and/or postdup are in bestfree table.
         */
        dfp = xfs_dir2_data_freefind(hdr, prevdup);
        dfp2 = xfs_dir2_data_freefind(hdr, postdup);
        /*
         * We need a rescan unless there are exactly 2 free entries
         * namely our two.  Then we know what's happening, otherwise
         * since the third bestfree is there, there might be more
         * entries.
         */
        needscan = (hdr->bestfree[2].length != 0);
        /*
         * Fix up the new big freespace.
         */
        be16_add_cpu(&prevdup->length, len + be16_to_cpu(postdup->length));
        *xfs_dir2_data_unused_tag_p(prevdup) =
            cpu_to_be16((char *)prevdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, prevdup);
        if (!needscan) {
            /*
             * Has to be the case that entries 0 and 1 are
             * dfp and dfp2 (don't know which is which), and
             * entry 2 is empty.
             * Remove entry 1 first then entry 0.
             */
            ASSERT(dfp && dfp2);
            if (dfp == &hdr->bestfree[1]) {
                dfp = &hdr->bestfree[0];
                ASSERT(dfp2 == dfp);
                dfp2 = &hdr->bestfree[1];
            }
            xfs_dir2_data_freeremove(hdr, dfp2, needlogp);
            xfs_dir2_data_freeremove(hdr, dfp, needlogp);
            /*
             * Now insert the new entry.
             */
            dfp = xfs_dir2_data_freeinsert(hdr, prevdup, needlogp);
            ASSERT(dfp == &hdr->bestfree[0]);
            ASSERT(dfp->length == prevdup->length);
            ASSERT(!dfp[1].length);
            ASSERT(!dfp[2].length);
        }
    }
    /*
     * The entry before us is free, merge with it.
     */
    else if (prevdup) {
        dfp = xfs_dir2_data_freefind(hdr, prevdup);
        be16_add_cpu(&prevdup->length, len);
        *xfs_dir2_data_unused_tag_p(prevdup) =
            cpu_to_be16((char *)prevdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, prevdup);
        /*
         * If the previous entry was in the table, the new entry
         * is longer, so it will be in the table too.  Remove
         * the old one and add the new one.
         */
        if (dfp) {
            xfs_dir2_data_freeremove(hdr, dfp, needlogp);
            xfs_dir2_data_freeinsert(hdr, prevdup, needlogp);
        }
        /*
         * Otherwise we need a scan if the new entry is big enough.
         */
        else {
            needscan = be16_to_cpu(prevdup->length) >
                   be16_to_cpu(hdr->bestfree[2].length);
        }
    }
    /*
     * The following entry is free, merge with it.
     */
    else if (postdup) {
        dfp = xfs_dir2_data_freefind(hdr, postdup);
        newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset);
        newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
        newdup->length = cpu_to_be16(len + be16_to_cpu(postdup->length));
        *xfs_dir2_data_unused_tag_p(newdup) =
            cpu_to_be16((char *)newdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup);
        /*
         * If the following entry was in the table, the new entry
         * is longer, so it will be in the table too.  Remove
         * the old one and add the new one.
         */
        if (dfp) {
            xfs_dir2_data_freeremove(hdr, dfp, needlogp);
            xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
        }
        /*
         * Otherwise we need a scan if the new entry is big enough.
         */
        else {
            needscan = be16_to_cpu(newdup->length) >
                   be16_to_cpu(hdr->bestfree[2].length);
        }
    }
    /*
     * Neither neighbor is free.  Make a new entry.
     */
    else {
        newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset);
        newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
        newdup->length = cpu_to_be16(len);
        *xfs_dir2_data_unused_tag_p(newdup) =
            cpu_to_be16((char *)newdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup);
        xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
    }
    *needscanp = needscan;
}

/*
 * Take a byte range out of an existing unused space and make it un-free.
 */
void
xfs_dir2_data_use_free(
    struct xfs_trans    *tp,
    struct xfs_buf      *bp,
    xfs_dir2_data_unused_t  *dup,       /* unused entry */
    xfs_dir2_data_aoff_t    offset,     /* starting offset to use */
    xfs_dir2_data_aoff_t    len,        /* length to use */
    int         *needlogp,  /* out: need to log header */
    int         *needscanp) /* out: need regen bestfree */
{
    xfs_dir2_data_hdr_t *hdr;       /* data block header */
    xfs_dir2_data_free_t    *dfp;       /* bestfree pointer */
    int         matchback;  /* matches end of freespace */
    int         matchfront; /* matches start of freespace */
    int         needscan;   /* need to regen bestfree */
    xfs_dir2_data_unused_t  *newdup;    /* new unused entry */
    xfs_dir2_data_unused_t  *newdup2;   /* another new unused entry */
    int         oldlen;     /* old unused entry's length */

    hdr = bp->b_addr;
    ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
           hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
    ASSERT(be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG);
    ASSERT(offset >= (char *)dup - (char *)hdr);
    ASSERT(offset + len <= (char *)dup + be16_to_cpu(dup->length) - (char *)hdr);
    ASSERT((char *)dup - (char *)hdr == be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)));
    /*
     * Look up the entry in the bestfree table.
     */
    dfp = xfs_dir2_data_freefind(hdr, dup);
    oldlen = be16_to_cpu(dup->length);
    ASSERT(dfp || oldlen <= be16_to_cpu(hdr->bestfree[2].length));
    /*
     * Check for alignment with front and back of the entry.
     */
    matchfront = (char *)dup - (char *)hdr == offset;
    matchback = (char *)dup + oldlen - (char *)hdr == offset + len;
    ASSERT(*needscanp == 0);
    needscan = 0;
    /*
     * If we matched it exactly we just need to get rid of it from
     * the bestfree table.
     */
    if (matchfront && matchback) {
        if (dfp) {
            needscan = (hdr->bestfree[2].offset != 0);
            if (!needscan)
                xfs_dir2_data_freeremove(hdr, dfp, needlogp);
        }
    }
    /*
     * We match the first part of the entry.
     * Make a new entry with the remaining freespace.
     */
    else if (matchfront) {
        newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
        newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
        newdup->length = cpu_to_be16(oldlen - len);
        *xfs_dir2_data_unused_tag_p(newdup) =
            cpu_to_be16((char *)newdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup);
        /*
         * If it was in the table, remove it and add the new one.
         */
        if (dfp) {
            xfs_dir2_data_freeremove(hdr, dfp, needlogp);
            dfp = xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
            ASSERT(dfp != NULL);
            ASSERT(dfp->length == newdup->length);
            ASSERT(be16_to_cpu(dfp->offset) == (char *)newdup - (char *)hdr);
            /*
             * If we got inserted at the last slot,
             * that means we don't know if there was a better
             * choice for the last slot, or not.  Rescan.
             */
            needscan = dfp == &hdr->bestfree[2];
        }
    }
    /*
     * We match the last part of the entry.
     * Trim the allocated space off the tail of the entry.
     */
    else if (matchback) {
        newdup = dup;
        newdup->length = cpu_to_be16(((char *)hdr + offset) - (char *)newdup);
        *xfs_dir2_data_unused_tag_p(newdup) =
            cpu_to_be16((char *)newdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup);
        /*
         * If it was in the table, remove it and add the new one.
         */
        if (dfp) {
            xfs_dir2_data_freeremove(hdr, dfp, needlogp);
            dfp = xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
            ASSERT(dfp != NULL);
            ASSERT(dfp->length == newdup->length);
            ASSERT(be16_to_cpu(dfp->offset) == (char *)newdup - (char *)hdr);
            /*
             * If we got inserted at the last slot,
             * that means we don't know if there was a better
             * choice for the last slot, or not.  Rescan.
             */
            needscan = dfp == &hdr->bestfree[2];
        }
    }
    /*
     * Poking out the middle of an entry.
     * Make two new entries.
     */
    else {
        newdup = dup;
        newdup->length = cpu_to_be16(((char *)hdr + offset) - (char *)newdup);
        *xfs_dir2_data_unused_tag_p(newdup) =
            cpu_to_be16((char *)newdup - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup);
        newdup2 = (xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
        newdup2->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
        newdup2->length = cpu_to_be16(oldlen - len - be16_to_cpu(newdup->length));
        *xfs_dir2_data_unused_tag_p(newdup2) =
            cpu_to_be16((char *)newdup2 - (char *)hdr);
        xfs_dir2_data_log_unused(tp, bp, newdup2);
        /*
         * If the old entry was in the table, we need to scan
         * if the 3rd entry was valid, since these entries
         * are smaller than the old one.
         * If we don't need to scan that means there were 1 or 2
         * entries in the table, and removing the old and adding
         * the 2 new will work.
         */
        if (dfp) {
            needscan = (hdr->bestfree[2].length != 0);
            if (!needscan) {
                xfs_dir2_data_freeremove(hdr, dfp, needlogp);
                xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
                xfs_dir2_data_freeinsert(hdr, newdup2,
                             needlogp);
            }
        }
    }
    *needscanp = needscan;
}