Patch for quota deadlock

[Kris Kennaway]

On Tue, Feb 28, 2006 at 05:00:40AM -0500, Kris Kennaway wrote:
> On Tue, Feb 28, 2006 at 11:58:02AM +0200, Niki Denev wrote:
> > On Tuesday 28 February 2006 09:51, Kris Kennaway wrote:
> > > On Tue, Feb 28, 2006 at 08:40:37AM +0100, Oliver Brandmueller wrote:
> > > > Anyway, I'll discuss with my colleagues and we'll see if we want to take
> > > > the risk.
> > >
> > > Thanks, it would be a big help if you're willing to try.
> > >
> > > Kris
> > 
> > I'm jumping here from the [snaphost timestamps] thread.
> > 
> > Here is what happened when i compiled the kernel with QUOTAS enabled, 
> > enable_quotas="YES" in rc.conf, and LK_NOWAIT patch applied :
> 
> > Enabling quotas:KDB: stack backtrace:
> > vfs_badlock() at vfs_badlock+0x95
> > assert_vop_locked() at assert_vop_locked+0x77
> > quotaon() at quotaon+0x182
> > ufs_quotactl() at ufs_quotactl+0x150
> > quotactl() at quotactl+0x15c
> > syscall() at syscall+0x642
> > Xfast_syscall() at Xfast_syscall+0xa8
> > --- syscall (148, FreeBSD ELF64, quotactl), rip = 0x80068671c, rsp = 
> 
> Thanks, I forgot about this.  You'll need these patches too:
> 
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/ufs/ufs/ufs_quota.c.diff?r1=1.77&r2=1.78
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/ufs/ufs/ufs_quota.c.diff?r1=1.78&r2=1.79

Here is the combined patch, without the $FreeBSD$ bits that won't
apply on RELENG_6:

Index: ufs_quota.c
===================================================================
RCS file: /home/ncvs/src/sys/ufs/ufs/ufs_quota.c,v
retrieving revision 1.77
retrieving revision 1.80
diff -u -u -r1.77 -r1.80
--- ufs_quota.c	9 Jan 2006 20:42:19 -0000	1.77
+++ ufs_quota.c	22 Feb 2006 06:12:53 -0000	1.80
@@ -429,8 +429,9 @@
 		quotaoff(td, mp, type);
 	ump->um_qflags[type] |= QTF_OPENING;
 	mp->mnt_flag |= MNT_QUOTA;
-	ASSERT_VOP_LOCKED(vp, "quotaon");
+	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
 	vp->v_vflag |= VV_SYSTEM;
+	VOP_UNLOCK(vp, 0, td);
 	*vpp = vp;
 	/*
 	 * Save the credential of the process that turned on quotas.
@@ -535,8 +536,9 @@
 	}
 	MNT_IUNLOCK(mp);
 	dqflush(qvp);
-	ASSERT_VOP_LOCKED(qvp, "quotaoff");
+	vn_lock(qvp, LK_EXCLUSIVE | LK_RETRY, td);
 	qvp->v_vflag &= ~VV_SYSTEM;
+	VOP_UNLOCK(qvp, 0, td);
 	error = vn_close(qvp, FREAD|FWRITE, td->td_ucred, td);
 	ump->um_quotas[type] = NULLVP;
 	crfree(ump->um_cred[type]);
@@ -748,7 +750,7 @@
 			MNT_ILOCK(mp);
 			continue;
 		}
-		error = vget(vp, LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, td);
+		error = vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, td);
 		if (error) {
 			MNT_ILOCK(mp);
 			if (error == ENOENT) {

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