jimzah/freebsd-src
1
0
Fork 0
mirror of https://github.com/freebsd/freebsd-src.git synced 2024-11-29 17:32:43 +00:00
Code Issues Actions 2 Packages Projects Releases Wiki Activity

Quick-hack to avoid `lock against myself' panic. It is not the real

Browse Source 
fix!

The ufs_link() assumes that vnode is not unlocked and tries to lock it
in certain case.  Because union_link calls VOP_LINK after locking vnode,
vn_lock in ufs_link causes above panic.

Currently, I don't know the real fix for a locking violation in
union_link, but I think it is important to avoid panic.

A vnode is unlocked before calling VOP_LINK and is locked after it if
the vnode is not union fs.  Even though panic went away, the process
that access the union fs in which link was made will hang-up.

Hang-up can be easily reproduced by following operation:

	mount -t union a b
	cd b
	ln foo bar
	ls
This commit is contained in:
KATO Takenori 1997-04-15 12:56:57 +00:00
parent 666a6cbbb1
commit 9095719e2b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=24963
2 changed files with 30 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
sys/fs/unionfs/union_vnops.c
View File

@ -35,7 +35,7 @@
* SUCH DAMAGE.
*
* @(#)union_vnops.c 8.32 (Berkeley) 6/23/95
* $Id: union_vnops.c,v 1.22 1997/04/13 13:12:12 kato Exp $
* $Id: union_vnops.c,v 1.23 1997/04/14 05:13:55 kato Exp $
*/
#include <sys/param.h>
@ -1058,6 +1058,7 @@ union_link(ap)
struct union_node *un;
struct vnode *vp;
struct vnode *tdvp;
int isvnunlocked = 0;
un = VTOUNION(ap->a_tdvp);
@ -1096,7 +1097,19 @@ union_link(ap)
un->un_flags |= UN_KLOCK;
vput(ap->a_tdvp);
return (VOP_LINK(vp, tdvp, cnp));
/*
* XXX -- This is a quick-hack to avoid panic. Problem still remains!
* The process which access the union filesystem will be hang-up after
* making link in the union fs.
*/
if (VOP_ISLOCKED(tdvp) && (tdvp->v_op != union_vnodeop_p)) {
isvnunlocked = 1;
VOP_UNLOCK(tdvp, 0, p);
}
error = VOP_LINK(vp, tdvp, cnp);
if (isvnunlocked)
vn_lock(tdvp, LK_EXCLUSIVE | LK_RETRY, p);
return error;
}
int

17
sys/miscfs/union/union_vnops.c
View File

@ -35,7 +35,7 @@
* SUCH DAMAGE.
*
* @(#)union_vnops.c 8.32 (Berkeley) 6/23/95
* $Id: union_vnops.c,v 1.22 1997/04/13 13:12:12 kato Exp $
* $Id: union_vnops.c,v 1.23 1997/04/14 05:13:55 kato Exp $
*/
#include <sys/param.h>
@ -1058,6 +1058,7 @@ union_link(ap)
struct union_node *un;
struct vnode *vp;
struct vnode *tdvp;
int isvnunlocked = 0;
un = VTOUNION(ap->a_tdvp);
@ -1096,7 +1097,19 @@ union_link(ap)
un->un_flags |= UN_KLOCK;
vput(ap->a_tdvp);
return (VOP_LINK(vp, tdvp, cnp));
/*
* XXX -- This is a quick-hack to avoid panic. Problem still remains!
* The process which access the union filesystem will be hang-up after
* making link in the union fs.
*/
if (VOP_ISLOCKED(tdvp) && (tdvp->v_op != union_vnodeop_p)) {
isvnunlocked = 1;
VOP_UNLOCK(tdvp, 0, p);
}
error = VOP_LINK(vp, tdvp, cnp);
if (isvnunlocked)
vn_lock(tdvp, LK_EXCLUSIVE | LK_RETRY, p);
return error;
}
int