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Fix a bug in ufsdirhash_adjfree() that caused it to incorrectly

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update the free-space statistics in some cases. The problem affected
directory blocks when the free space dropped below the size of the
maximum allowed entry size. When this happened, the free-space
summary information could claim that there are no further blocks
that can fit a maximum-size entry, even if there are.

The effect of this bug is that the directory may be enlarged even
though there is space within the directory for the new entry. This
wastes disk space and has a negative impact on performance.

Fix it by correctly computing the dh_firstfree array index, adding
a helper macro for clarity. Put an extra sanity check into
ufsdirhash_checkblock() to detect the situation in future.

Found by:	dwmalone
Reviewed by:	dwmalone
MFC after:	1 week
This commit is contained in:
Ian Dowse 2002-03-11 19:13:22 +00:00
parent a2df0b493e
commit 23bd68a426
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=92098
1 changed files with 7 additions and 10 deletions
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17
sys/ufs/ufs/ufs_dirhash.c
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@ -57,6 +57,7 @@
#define WRAPINCR(val, limit) (((val) + 1 == (limit)) ? 0 : ((val) + 1))
#define OFSFMT(vp) ((vp)->v_mount->mnt_maxsymlinklen <= 0)
#define BLKFREE2IDX(n) ((n) > DH_NFSTATS ? DH_NFSTATS : (n))
static MALLOC_DEFINE(M_DIRHASH, "UFS dirhash", "UFS directory hash tables");
@ -845,12 +846,12 @@ ufsdirhash_checkblock(struct inode *ip, char *buf, doff_t offset)
if (dh->dh_blkfree[block] * DIRALIGN != nfree)
panic("ufsdirhash_checkblock: bad free count");
ffslot = nfree / DIRALIGN;
if (ffslot > DH_NFSTATS)
ffslot = DH_NFSTATS;
ffslot = BLKFREE2IDX(nfree / DIRALIGN);
for (i = 0; i <= DH_NFSTATS; i++)
if (dh->dh_firstfree[i] == block && i != ffslot)
panic("ufsdirhash_checkblock: bad first-free");
if (dh->dh_firstfree[ffslot] == -1)
panic("ufsdirhash_checkblock: missing first-free entry");
mtx_unlock(&dh->dh_mtx);
}
@ -880,20 +881,16 @@ ufsdirhash_adjfree(struct dirhash *dh, doff_t offset, int diff)
block = offset / DIRBLKSIZ;
KASSERT(block < dh->dh_nblk && block < dh->dh_dirblks,
("dirhash bad offset"));
ofidx = dh->dh_blkfree[block];
if (ofidx > DH_NFSTATS)
ofidx = DH_NFSTATS;
ofidx = BLKFREE2IDX(dh->dh_blkfree[block]);
dh->dh_blkfree[block] = (int)dh->dh_blkfree[block] + (diff / DIRALIGN);
nfidx = dh->dh_blkfree[block];
if (nfidx > DH_NFSTATS)
nfidx = DH_NFSTATS;
nfidx = BLKFREE2IDX(dh->dh_blkfree[block]);
/* Update the `first free' list if necessary. */
if (ofidx != nfidx) {
/* If removing, scan forward for the next block. */
if (dh->dh_firstfree[ofidx] == block) {
for (i = block + 1; i < dh->dh_dirblks; i++)
if (dh->dh_blkfree[i] == ofidx)
if (BLKFREE2IDX(dh->dh_blkfree[i]) == ofidx)
break;
dh->dh_firstfree[ofidx] = (i < dh->dh_dirblks) ? i : -1;
}