Merge tag 'fixes-for-v3.9-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi...

[deliverable/linux.git] / fs / xfs / xfs_dir2_data.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_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);

/*
 * Check the consistency of the data block.
 * The input can also be a block-format directory.
 * Return 0 is the buffer is good, otherwise an error.
 */
int
__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 = bp->b_target->bt_mount;
        hdr = bp->b_addr;
        bf = hdr->bestfree;
        p = (char *)(hdr + 1);

        switch (hdr->magic) {
        case 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;
                break;
        case cpu_to_be32(XFS_DIR2_DATA_MAGIC):
                endp = (char *)hdr + mp->m_dirblksize;
                break;
        default:
                XFS_ERROR_REPORT("Bad Magic", XFS_ERRLEVEL_LOW, mp);
                return EFSCORRUPTED;
        }

        count = lastfree = freeseen = 0;
        /*
         * Account for zero bestfree entries.
         */
        if (!bf[0].length) {
                XFS_WANT_CORRUPTED_RETURN(!bf[0].offset);
                freeseen |= 1 << 0;
        }
        if (!bf[1].length) {
                XFS_WANT_CORRUPTED_RETURN(!bf[1].offset);
                freeseen |= 1 << 1;
        }
        if (!bf[2].length) {
                XFS_WANT_CORRUPTED_RETURN(!bf[2].offset);
                freeseen |= 1 << 2;
        }

        XFS_WANT_CORRUPTED_RETURN(be16_to_cpu(bf[0].length) >=
                                                be16_to_cpu(bf[1].length));
        XFS_WANT_CORRUPTED_RETURN(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) {
                        XFS_WANT_CORRUPTED_RETURN(lastfree == 0);
                        XFS_WANT_CORRUPTED_RETURN(
                                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);
                                XFS_WANT_CORRUPTED_RETURN(
                                        (freeseen & (1 << i)) == 0);
                                freeseen |= 1 << i;
                        } else {
                                XFS_WANT_CORRUPTED_RETURN(
                                        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;
                XFS_WANT_CORRUPTED_RETURN(dep->namelen != 0);
                XFS_WANT_CORRUPTED_RETURN(
                        !xfs_dir_ino_validate(mp, be64_to_cpu(dep->inumber)));
                XFS_WANT_CORRUPTED_RETURN(
                        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;
                        }
                        XFS_WANT_CORRUPTED_RETURN(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.
         */
        XFS_WANT_CORRUPTED_RETURN(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)
                                XFS_WANT_CORRUPTED_RETURN(
                                        be32_to_cpu(lep[i].hashval) >=
                                                be32_to_cpu(lep[i - 1].hashval));
                }
                XFS_WANT_CORRUPTED_RETURN(count ==
                        be32_to_cpu(btp->count) - be32_to_cpu(btp->stale));
                XFS_WANT_CORRUPTED_RETURN(stale == be32_to_cpu(btp->stale));
        }
        return 0;
}

static void
xfs_dir2_data_verify(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_dir2_data_hdr *hdr = bp->b_addr;
        int                     block_ok = 0;

        block_ok = hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC);
        block_ok = block_ok && __xfs_dir2_data_check(NULL, bp) == 0;

        if (!block_ok) {
                XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, hdr);
                xfs_buf_ioerror(bp, EFSCORRUPTED);
        }
}

/*
 * Readahead of the first block of the directory when it is opened is completely
 * oblivious to the format of the directory. Hence we can either get a block
 * format buffer or a data format buffer on readahead.
 */
static void
xfs_dir2_data_reada_verify(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_dir2_data_hdr *hdr = bp->b_addr;

        switch (hdr->magic) {
        case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC):
                bp->b_ops = &xfs_dir2_block_buf_ops;
                bp->b_ops->verify_read(bp);
                return;
        case cpu_to_be32(XFS_DIR2_DATA_MAGIC):
                xfs_dir2_data_verify(bp);
                return;
        default:
                XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, hdr);
                xfs_buf_ioerror(bp, EFSCORRUPTED);
                break;
        }
}

static void
xfs_dir2_data_read_verify(
        struct xfs_buf  *bp)
{
        xfs_dir2_data_verify(bp);
}

static void
xfs_dir2_data_write_verify(
        struct xfs_buf  *bp)
{
        xfs_dir2_data_verify(bp);
}

const struct xfs_buf_ops xfs_dir2_data_buf_ops = {
        .verify_read = xfs_dir2_data_read_verify,
        .verify_write = xfs_dir2_data_write_verify,
};

static const struct xfs_buf_ops xfs_dir2_data_reada_buf_ops = {
        .verify_read = xfs_dir2_data_reada_verify,
        .verify_write = xfs_dir2_data_write_verify,
};


int
xfs_dir2_data_read(
        struct xfs_trans        *tp,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        xfs_daddr_t             mapped_bno,
        struct xfs_buf          **bpp)
{
        return xfs_da_read_buf(tp, dp, bno, mapped_bno, bpp,
                                XFS_DATA_FORK, &xfs_dir2_data_buf_ops);
}

int
xfs_dir2_data_readahead(
        struct xfs_trans        *tp,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        xfs_daddr_t             mapped_bno)
{
        return xfs_da_reada_buf(tp, dp, bno, mapped_bno,
                                XFS_DATA_FORK, &xfs_dir2_data_reada_buf_ops);
}

/*
 * 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;
        bp->b_ops = &xfs_dir2_data_buf_ops;

        /*
         * 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;
}