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When restoring the mount after umount failed, the MNTK_UNMOUNT flag

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prevents insmntque() from placing reallocated syncer vnode on mount
list, that causes panic in vfs_allocate_syncvnode().

Introduce MNTK_NOINSMNTQ flag, that marks the period when instmntque is
not allowed to success, instead of MNTK_UNMOUNT. The MNTK_NOINSMNTQ is
set and cleared simultaneously with MNTK_UNMOUNT, except on umount error
path, where it is cleaned just before the syncer vnode is going to be
allocated.

Reported by:	Peter Jeremy <peterjeremy optushome com au>
Suggested by:	tegge
Approved by:	re (rwatson)
This commit is contained in:
Konstantin Belousov 2007-09-12 16:31:32 +00:00
parent b28624fde6
commit 245b204491
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=172151
3 changed files with 15 additions and 5 deletions
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13
sys/kern/vfs_mount.c
View File

@ -1222,7 +1222,7 @@ dounmount(mp, flags, td)
VOP_UNLOCK(coveredvp, 0, td);
return (EBUSY);
}
mp->mnt_kern_flag |= MNTK_UNMOUNT;
mp->mnt_kern_flag |= MNTK_UNMOUNT | MNTK_NOINSMNTQ;
/* Allow filesystems to detect that a forced unmount is in progress. */
if (flags & MNT_FORCE)
mp->mnt_kern_flag |= MNTK_UNMOUNTF;
@ -1230,7 +1230,8 @@ dounmount(mp, flags, td)
((flags & MNT_FORCE) ? 0 : LK_NOWAIT), MNT_MTX(mp), td);
if (error) {
MNT_ILOCK(mp);
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_NOINSMNTQ |
MNTK_UNMOUNTF);
if (mp->mnt_kern_flag & MNTK_MWAIT)
wakeup(mp);
MNT_IUNLOCK(mp);
@ -1285,9 +1286,13 @@ dounmount(mp, flags, td)
}
vput(fsrootvp);
}
if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL)
(void) vfs_allocate_syncvnode(mp);
MNT_ILOCK(mp);
mp->mnt_kern_flag &= ~MNTK_NOINSMNTQ;
if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL) {
MNT_IUNLOCK(mp);
(void) vfs_allocate_syncvnode(mp);
MNT_ILOCK(mp);
}
mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
mp->mnt_flag |= async_flag;
if ((mp->mnt_flag & MNT_ASYNC) != 0 && mp->mnt_noasync == 0)

2
sys/kern/vfs_subr.c
View File

@ -1021,7 +1021,7 @@ insmntque1(struct vnode *vp, struct mount *mp,
("insmntque: vnode already on per mount vnode list"));
VNASSERT(mp != NULL, vp, ("Don't call insmntque(foo, NULL)"));
MNT_ILOCK(mp);
if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0 &&
if ((mp->mnt_kern_flag & MNTK_NOINSMNTQ) != 0 &&
mp->mnt_nvnodelistsize == 0) {
MNT_IUNLOCK(mp);
if (dtr != NULL)

5
sys/sys/mount.h
View File

@ -303,10 +303,15 @@ void __mnt_vnode_markerfree(struct vnode **mvp, struct mount *mp);
* dounmount() is still waiting to lock the mountpoint. This allows
* the filesystem to cancel operations that might otherwise deadlock
* with the unmount attempt (used by NFS).
*
* MNTK_NOINSMNTQ is strict subset of MNTK_UNMOUNT. They are separated
* to allow for failed unmount attempt to restore the syncer vnode for
* the mount.
*/
#define MNTK_UNMOUNTF 0x00000001 /* forced unmount in progress */
#define MNTK_ASYNC 0x00000002 /* filtered async flag */
#define MNTK_SOFTDEP 0x00000004 /* async disabled by softdep */
#define MNTK_NOINSMNTQ 0x00000008 /* insmntque is not allowed */
#define MNTK_UNMOUNT 0x01000000 /* unmount in progress */
#define MNTK_MWAIT 0x02000000 /* waiting for unmount to finish */
#define MNTK_SUSPEND 0x08000000 /* request write suspension */