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Implement the async (really, delayed-write) mount option for msdosfs.

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This is much simpler than for ffs since there are many fewer places
where we need to choose between a delayed write and a sync write --
just 5 in msdosfs and more than 30 in ffs.

This is more complete and correct than in ffs.  Several places in ffs
are are still missing the choice.  ffs_update() has a layering violation
that breaks callers which want to force a sync update (mainly fsync(2)
and O_SYNC write(2)).

However, fsync(2) and O_SYNC write(2) are still more broken than in
ffs, since they are broken for default (non-sync non-async) mounts
too.  Both fail to sync the FAT in all cases, and both fail to sync
the directory entry in some cases after losing a race.  Async everything
is probably safer than the half-baked sync of metadata given by default
mounts.
This commit is contained in:
Bruce Evans 2007-10-19 12:23:25 +00:00
parent 28c8ed2488
commit cb65c1ee29
4 changed files with 18 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
sys/fs/msdosfs/msdosfs_denode.c
View File

@ -429,7 +429,7 @@ detrunc(dep, length, flags, cred, td)
if (allerror)
printf("detrunc(): vtruncbuf error %d\n", allerror);
#endif
error = deupdat(dep, 1);
error = deupdat(dep, !(DETOV(dep)->v_mount->mnt_flag & MNT_ASYNC));
if (error != 0 && allerror == 0)
allerror = error;
#ifdef MSDOSFS_DEBUG
@ -508,7 +508,7 @@ deextend(dep, length, cred)
}
dep->de_FileSize = length;
dep->de_flag |= DE_UPDATE | DE_MODIFIED;
return (deupdat(dep, 1));
return (deupdat(dep, !(DETOV(dep)->v_mount->mnt_flag & MNT_ASYNC)));
}
/*

12
sys/fs/msdosfs/msdosfs_lookup.c
View File

@ -625,7 +625,9 @@ createde(dep, ddep, depp, cnp)
while (--ddep->de_fndcnt >= 0) {
if (!(ddep->de_fndoffset & pmp->pm_crbomask)) {
if ((error = bwrite(bp)) != 0)
if (DETOV(ddep)->v_mount->mnt_flag & MNT_ASYNC)
bdwrite(bp);
else if ((error = bwrite(bp)) != 0)
return error;
ddep->de_fndoffset -= sizeof(struct direntry);
@ -653,7 +655,9 @@ createde(dep, ddep, depp, cnp)
}
}
if ((error = bwrite(bp)) != 0)
if (DETOV(ddep)->v_mount->mnt_flag & MNT_ASYNC)
bdwrite(bp);
else if ((error = bwrite(bp)) != 0)
return error;
/*
@ -951,7 +955,9 @@ removede(pdep, dep)
|| ep->deAttributes != ATTR_WIN95)
break;
}
if ((error = bwrite(bp)) != 0)
if (DETOV(pdep)->v_mount->mnt_flag & MNT_ASYNC)
bdwrite(bp);
else if ((error = bwrite(bp)) != 0)
return error;
} while (!(pmp->pm_flags & MSDOSFSMNT_NOWIN95)
&& !(offset & pmp->pm_crbomask)

2
sys/fs/msdosfs/msdosfs_vfsops.c
View File

@ -76,7 +76,7 @@
/* Mount options that we support. */
static const char *msdosfs_opts[] = {
"noatime", "noclusterr", "noclusterw",
"async", "noatime", "noclusterr", "noclusterw",
"export", "force", "from", "sync",
"cs_dos", "cs_local", "cs_win", "dirmask",
"gid", "kiconv", "large", "longname",

10
sys/fs/msdosfs/msdosfs_vnops.c
View File

@ -1265,8 +1265,9 @@ msdosfs_rename(ap)
putushort(dotdotp->deStartCluster, dp->de_StartCluster);
if (FAT32(pmp))
putushort(dotdotp->deHighClust, dp->de_StartCluster >> 16);
error = bwrite(bp);
if (error) {
if (fvp->v_mount->mnt_flag & MNT_ASYNC)
bdwrite(bp);
else if ((error = bwrite(bp)) != 0) {
/* XXX should downgrade to ro here, fs is corrupt */
VOP_UNLOCK(fvp, 0, td);
goto bad;
@ -1390,8 +1391,9 @@ msdosfs_mkdir(ap)
putushort(denp[1].deHighClust, pdep->de_StartCluster >> 16);
}
error = bwrite(bp);
if (error)
if (ap->a_dvp->v_mount->mnt_flag & MNT_ASYNC)
bdwrite(bp);
else if ((error = bwrite(bp)) != 0)
goto bad;
/*