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Avoid `lock against myself' panic by following operation:

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# mount -t union (or null) dir1 dir2
	# mount -t union (or null) dir2 dir1

The function namei in union_mount calls union_root.  The upper vnode
has been already locked and vn_lock in union_root causes above panic.

Add printf's included in `#ifdef DIAGNOSTIC' for EDEADLK cases.
This commit is contained in:
KATO Takenori 1997-04-19 06:04:13 +00:00
parent e747d90dbf
commit 747e915757
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=25016
4 changed files with 66 additions and 12 deletions
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21
sys/fs/nullfs/null_vfsops.c
View File

@ -36,7 +36,7 @@
* @(#)null_vfsops.c 8.2 (Berkeley) 1/21/94 * @(#)null_vfsops.c 8.2 (Berkeley) 1/21/94
* *
* @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92 * @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92
* $Id: null_vfsops.c,v 1.15 1997/04/17 11:17:29 kato Exp $ * $Id: null_vfsops.c,v 1.16 1997/04/17 11:24:57 kato Exp $
*/ */
/* /*
@ -149,8 +149,10 @@ nullfs_mount(mp, path, data, ndp, p)
* Check multi null mount to avoid `lock against myself' panic. * Check multi null mount to avoid `lock against myself' panic.
*/ */
if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) { if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) {
error = EDEADLK; #ifdef DIAGNOSTIC
return (error); printf("nullfs_mount: multi null mount?\n");
#endif
return (EDEADLK);
} }
xmp = (struct null_mount *) malloc(sizeof(struct null_mount), xmp = (struct null_mount *) malloc(sizeof(struct null_mount),
@ -293,7 +295,18 @@ nullfs_root(mp, vpp)
*/ */
vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp; vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
VREF(vp); VREF(vp);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); if (VOP_ISLOCKED(vp)) {
/*
* XXX
* Should we check type of node?
*/
#ifdef DIAGNOSTIC
printf("nullfs_root: multi null mount?\n");
#endif
vrele(vp);
return (EDEADLK);
} else
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
*vpp = vp; *vpp = vp;
return 0; return 0;
} }

18
sys/fs/unionfs/union_vfsops.c
View File

@ -35,7 +35,7 @@
* SUCH DAMAGE. * SUCH DAMAGE.
* *
* @(#)union_vfsops.c 8.20 (Berkeley) 5/20/95 * @(#)union_vfsops.c 8.20 (Berkeley) 5/20/95
* $Id: union_vfsops.c,v 1.14 1997/02/22 09:40:41 peter Exp $ * $Id: union_vfsops.c,v 1.15 1997/04/14 10:52:25 kato Exp $
*/ */
/* /*
@ -161,6 +161,9 @@ union_mount(mp, path, data, ndp, p)
* Check multi union mount to avoid `lock myself again' panic. * Check multi union mount to avoid `lock myself again' panic.
*/ */
if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) { if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) {
#ifdef DIAGNOSTIC
printf("union_mount: multi union mount?\n");
#endif
error = EDEADLK; error = EDEADLK;
goto bad; goto bad;
} }
@ -408,7 +411,18 @@ union_root(mp, vpp)
VOP_ISLOCKED(um->um_uppervp)) { VOP_ISLOCKED(um->um_uppervp)) {
loselock = 1; loselock = 1;
} else { } else {
vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p); if (VOP_ISLOCKED(um->um_uppervp)) {
/*
* XXX
* Should we check type of node?
*/
#ifdef DIAGNOSTIC
printf("union_root: multi union mount?");
#endif
vrele(um->um_uppervp);
return EDEADLK;
} else
vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
loselock = 0; loselock = 0;
} }
if (um->um_lowervp) if (um->um_lowervp)

21
sys/miscfs/nullfs/null_vfsops.c
View File

@ -36,7 +36,7 @@
* @(#)null_vfsops.c 8.2 (Berkeley) 1/21/94 * @(#)null_vfsops.c 8.2 (Berkeley) 1/21/94
* *
* @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92 * @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92
* $Id: null_vfsops.c,v 1.15 1997/04/17 11:17:29 kato Exp $ * $Id: null_vfsops.c,v 1.16 1997/04/17 11:24:57 kato Exp $
*/ */
/* /*
@ -149,8 +149,10 @@ nullfs_mount(mp, path, data, ndp, p)
* Check multi null mount to avoid `lock against myself' panic. * Check multi null mount to avoid `lock against myself' panic.
*/ */
if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) { if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) {
error = EDEADLK; #ifdef DIAGNOSTIC
return (error); printf("nullfs_mount: multi null mount?\n");
#endif
return (EDEADLK);
} }
xmp = (struct null_mount *) malloc(sizeof(struct null_mount), xmp = (struct null_mount *) malloc(sizeof(struct null_mount),
@ -293,7 +295,18 @@ nullfs_root(mp, vpp)
*/ */
vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp; vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
VREF(vp); VREF(vp);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); if (VOP_ISLOCKED(vp)) {
/*
* XXX
* Should we check type of node?
*/
#ifdef DIAGNOSTIC
printf("nullfs_root: multi null mount?\n");
#endif
vrele(vp);
return (EDEADLK);
} else
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
*vpp = vp; *vpp = vp;
return 0; return 0;
} }

18
sys/miscfs/union/union_vfsops.c
View File

@ -35,7 +35,7 @@
* SUCH DAMAGE. * SUCH DAMAGE.
* *
* @(#)union_vfsops.c 8.20 (Berkeley) 5/20/95 * @(#)union_vfsops.c 8.20 (Berkeley) 5/20/95
* $Id: union_vfsops.c,v 1.14 1997/02/22 09:40:41 peter Exp $ * $Id: union_vfsops.c,v 1.15 1997/04/14 10:52:25 kato Exp $
*/ */
/* /*
@ -161,6 +161,9 @@ union_mount(mp, path, data, ndp, p)
* Check multi union mount to avoid `lock myself again' panic. * Check multi union mount to avoid `lock myself again' panic.
*/ */
if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) { if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) {
#ifdef DIAGNOSTIC
printf("union_mount: multi union mount?\n");
#endif
error = EDEADLK; error = EDEADLK;
goto bad; goto bad;
} }
@ -408,7 +411,18 @@ union_root(mp, vpp)
VOP_ISLOCKED(um->um_uppervp)) { VOP_ISLOCKED(um->um_uppervp)) {
loselock = 1; loselock = 1;
} else { } else {
vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p); if (VOP_ISLOCKED(um->um_uppervp)) {
/*
* XXX
* Should we check type of node?
*/
#ifdef DIAGNOSTIC
printf("union_root: multi union mount?");
#endif
vrele(um->um_uppervp);
return EDEADLK;
} else
vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
loselock = 0; loselock = 0;
} }
if (um->um_lowervp) if (um->um_lowervp)