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

Tejun Heo
2007-04-24T20:16:05Z

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@gmail.com> wrote:
>
> > Andrew Morton wrote:
> > > On Wed, 25 Apr 2007 01:33:59 +0900 Tejun Heo <htejun@gmail.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);