linux-kernel - Re: [OOPS 2.6.21-rc7-mm1] kernel BUG at fs/sysfs/inode.c:272 (sysfs_drop

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Date:	Wed, 25 Apr 2007 05:15:55 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Vincent Vanackere <vincent.vanackere@...il.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...e.de>
Subject: Re: [OOPS 2.6.21-rc7-mm1] kernel BUG at fs/sysfs/inode.c:272 (sysfs_drop_dentry)

On Tue, Apr 24, 2007 at 10:58:44AM -0700, Andrew Morton wrote:
> On Wed, 25 Apr 2007 02:51:43 +0900 Tejun Heo <htejun@...il.com> wrote:
> 
> > Andrew Morton wrote:
> > > On Wed, 25 Apr 2007 01:33:59 +0900 Tejun Heo <htejun@...il.com> wrote:
> > > 
> > >> Vincent Vanackere wrote:
> > >>> Hi,
> > >>>
> > >>> I'm getting the following oops at boot with the latest -mm kernel :
> > >>> ---------------------------------------------------------------
> > >>> kernel BUG at fs/sysfs/inode.c:272
> > >> Known problem.  Working on it.  Thanks.
> > >>
> > > 
> > > If it had been known by me I wouldn't have released known-buggy code to
> > > people who need to be able to test other people's code too. (argh)
> > > 
> > 
> > It's the problem Cornelia reported in the thread the patch was posted.
> 
> Is there a workaround?  What might happen if we just delete that BUG_ON()?

Okay, here's the workaround.  It leaks dentries and inodes if parent
is deleted first but other than that it should be okay.

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index eea50a5..b466671 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -212,8 +212,11 @@ static struct dentry *sysfs_lookup_sd(struct sysfs_dirent *sd)
 	depth = sysfs_path_depth(sd);
 
 	while (depth--) {
-		/* negative intermediate node is a BUG */
-		BUG_ON(!dentry->d_inode);
+		/* XXX */ /* negative intermediate node is a BUG */
+		/* XXX */ /* BUG_ON(!dentry->d_inode); */
+		if (!dentry->d_inode)
+			return NULL;
+		/* XXX */
 
 		for (cur = sd, i = 0; i < depth; i++)
 			cur = cur->s_parent;
@@ -269,7 +272,7 @@ void sysfs_drop_dentry(struct sysfs_dirent *sd)
 	}
 
 	if (isdir) {
-		BUG_ON(!simple_empty(dentry));
+		/* XXX */ /* BUG_ON(!simple_empty(dentry)); */
 		drop_nlink(dir);
 		/* unpin if directory */
 		dput(dentry);
-
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