On Tue, 14 Aug 2012 18:48:35 +0000
"Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote:
> On Tue, 2012-08-14 at 19:35 +0100, Al Viro wrote:
> > On Tue, Aug 14, 2012 at 06:04:08PM +0000, Myklebust, Trond wrote:
> > > > Is this a known BUG ?
> > > > Which other information or test can I do to contribute searching/resolving this issue?
> > >
> > > I'm not 100% certain, but it looks to me as if the call to dget_parent()
> > > in nfs_lookup_revalidate is returning NULL.
> > >
> > > Could you please apply the following patch, and see if that triggers the
> > > WARN_ON instead of the above Oops?
> >
> > Unlikely as hell. dget_parent() has only one return in it, and it's
> > BUG_ON(!ret->d_count);
> > ret->d_count++;
> > spin_unlock(&ret->d_lock);
> > return ret;
> > so it's extremely unlikely that it would managed to return NULL. Not
> > without oopsing...
>
> Agreed, but the Oops is a NULL pointer dereference of offset 00038,
> which looks suspiciously like a deference of (struct dentry)->d_inode.
> There are only 2 of those in the vicinity of nfs_lookup_revalidate+0x2d:
> one is a dereference of parent->d_inode, the other is dentry->d_inode...
>
One way to determine this would be to follow the instructions here,
substituting nfs.ko for cifs.ko:
http://wiki.samba.org/index.php/LinuxCIFS_troubleshooting#Oopses
...and see if you can get a listing of the spot where it oopsed. You
may need kernel debuginfo installed if you're using a distro kernel
though.
[1]: yes, I know that page is about CIFS troubleshooting, but that
method should work for nfs.ko too.
--
Jeff Layton <jlayton@xxxxxxxxxx>
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