On Wed, 21 Sep 2011 14:53:12 -0400
Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> wrote:
> On Wed, 2011-09-21 at 11:58 -0400, Jeff Layton wrote:
> > We had a regression reported against RHEL concerning the opening of
> > directories and it looks like that same problem is in current mainline
> > code too. If you do the following on a directory that is not yet in the
> > dcache you get an EISDIR error:
> >
> > open("/mnt/nfs/dir1", O_RDONLY) = -1 EISDIR (Is a directory)
> >
> > If however, you stat the directory first, the open works. The
> > difference seems to be that in the first case we're going through the
> > lookup codepath, and in the second we go through d_revalidate.
> >
> > In the first case, we send an OPEN call to the server and it responds
> > with NFS4ERR_ISDIR. That gets translated to -EISDIR, and returned to
> > userspace. It wasn't always this way though, and I think the regression
> > was introduced in commit d953126a2.
> >
> > That patch was added to fix an oops due to a buggy server, and I'm
> > unclear on how best to fix this. It seems like we need to allow the
> > server to fall back to doing a normal lookup when we get -EISDIR on the
> > OPEN call, but how do we ensure that we don't end up with the same oops
> > from that server bug?
>
> How about returning an error if we get to the file->f_ops->open on a
> regular file in NFSv4?
>
That would probably be reasonable. I'll see if I can come up with a
patch. The tricky part of course is ensuring that nothing regresses...
I think this is probably safe for the most part. The d_revalidate
codepath has always allowed you to end up with an open context with
NULL state.
Granted the buggy server case here is exceedingly rare, but it seems
like the code already assumes that a ctx reached via filp may have a
NULL state pointer.
Thanks,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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