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Do not update the fsinfo block on each update of any fat block, this

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is excessive. Postpone the flush of the fsinfo to VFS_SYNC(),
remembering the need for update with the flag MSDOSFS_FSIMOD, stored
in pm_flags.

FAT32 specification describes both FSI_Free_Count and FSI_Nxt_Free as
the advisory hints, not requiring them to be correct.

Based on the patch from bde, modified by me.

Reviewed by: bde
MFC after:   2 weeks
This commit is contained in:
Konstantin Belousov 2013-02-17 20:35:54 +00:00
parent 43e1adfa05
commit bb7ca8229d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=246921
3 changed files with 45 additions and 30 deletions
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36
sys/fs/msdosfs/msdosfs_fat.c
View File

@ -328,29 +328,6 @@ updatefats(pmp, bp, fatbn)
printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn);
#endif
/*
* If we have an FSInfo block, update it.
*/
if (pmp->pm_fsinfo) {
if (bread(pmp->pm_devvp, pmp->pm_fsinfo, pmp->pm_BytesPerSec,
NOCRED, &bpn) != 0) {
/*
* Ignore the error, but turn off FSInfo update for the future.
*/
pmp->pm_fsinfo = 0;
brelse(bpn);
} else {
struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
putulong(fp->fsinfree, pmp->pm_freeclustercount);
putulong(fp->fsinxtfree, pmp->pm_nxtfree);
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bpn);
else
bdwrite(bpn);
}
}
if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
/*
* Now copy the block(s) of the modified fat to the other copies of
@ -393,9 +370,6 @@ updatefats(pmp, bp, fatbn)
bwrite(bp);
else
bdwrite(bp);
/*
* Maybe update fsinfo sector here?
*/
}
/*
@ -431,6 +405,7 @@ usemap_alloc(pmp, cn)
pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
KASSERT(pmp->pm_freeclustercount > 0, ("usemap_alloc: too little"));
pmp->pm_freeclustercount--;
pmp->pm_flags |= MSDOSFS_FSIMOD;
}
static __inline void
@ -441,6 +416,7 @@ usemap_free(pmp, cn)
MSDOSFS_ASSERT_MP_LOCKED(pmp);
pmp->pm_freeclustercount++;
pmp->pm_flags |= MSDOSFS_FSIMOD;
KASSERT((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
!= 0, ("Freeing unused sector %ld %ld %x", cn, cn % N_INUSEBITS,
(unsigned)pmp->pm_inusemap[cn / N_INUSEBITS]));
@ -742,7 +718,10 @@ chainalloc(pmp, start, count, fillwith, retcluster, got)
for (cl = start, n = count; n-- > 0;)
usemap_alloc(pmp, cl++);
pmp->pm_nxtfree = start + count;
if (pmp->pm_nxtfree > pmp->pm_maxcluster)
pmp->pm_nxtfree = CLUST_FIRST;
pmp->pm_flags |= MSDOSFS_FSIMOD;
error = fatchain(pmp, start, count, fillwith);
if (error != 0)
return (error);
@ -754,9 +733,6 @@ chainalloc(pmp, start, count, fillwith, retcluster, got)
*retcluster = start;
if (got)
*got = count;
pmp->pm_nxtfree = start + count;
if (pmp->pm_nxtfree > pmp->pm_maxcluster)
pmp->pm_nxtfree = CLUST_FIRST;
return (0);
}

38
sys/fs/msdosfs/msdosfs_vfsops.c
View File

@ -896,6 +896,40 @@ msdosfs_statfs(struct mount *mp, struct statfs *sbp)
return (0);
}
/*
* If we have an FSInfo block, update it.
*/
static int
msdosfs_fsiflush(struct msdosfsmount *pmp, int waitfor)
{
struct fsinfo *fp;
struct buf *bp;
int error;
MSDOSFS_LOCK_MP(pmp);
if (pmp->pm_fsinfo == 0 || (pmp->pm_flags & MSDOSFS_FSIMOD) == 0) {
error = 0;
goto unlock;
}
error = bread(pmp->pm_devvp, pmp->pm_fsinfo, pmp->pm_BytesPerSec,
NOCRED, &bp);
if (error != 0) {
brelse(bp);
goto unlock;
}
fp = (struct fsinfo *)bp->b_data;
putulong(fp->fsinfree, pmp->pm_freeclustercount);
putulong(fp->fsinxtfree, pmp->pm_nxtfree);
pmp->pm_flags &= ~MSDOSFS_FSIMOD;
if (waitfor == MNT_WAIT)
error = bwrite(bp);
else
bawrite(bp);
unlock:
MSDOSFS_UNLOCK_MP(pmp);
return (error);
}
static int
msdosfs_sync(struct mount *mp, int waitfor)
{
@ -958,6 +992,10 @@ msdosfs_sync(struct mount *mp, int waitfor)
allerror = error;
VOP_UNLOCK(pmp->pm_devvp, 0);
}
error = msdosfs_fsiflush(pmp, waitfor);
if (error != 0)
allerror = error;
return (allerror);
}

1
sys/fs/msdosfs/msdosfsmount.h
View File

@ -262,6 +262,7 @@ struct msdosfs_args {
#define MSDOSFSMNT_WAITONFAT 0x40000000 /* mounted synchronous */
#define MSDOSFS_FATMIRROR 0x20000000 /* FAT is mirrored */
#define MSDOSFS_LARGEFS 0x10000000 /* perform fileno mapping */
#define MSDOSFS_FSIMOD 0x01000000
#define MSDOSFS_ARGSMAGIC 0xe4eff300