Re: [PATCH 1/3] NFS: Don't invalidate a submounted dentry in nfs_prime_dcache()

[NeilBrown <neilb@suse.de>]

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On Mon, 23 Feb 2015 22:09:09 -0500 Trond Myklebust
<trond.myklebust@primarydata.com> wrote:

> On Mon, Feb 23, 2015 at 7:14 PM, Trond Myklebust
> <trond.myklebust@primarydata.com> wrote:
> > If we're traversing a directory which contains a submounted filesystem,
> > or one that has a referral, the NFS server that is processing the READDIR
> > request will often return information for the underlying (mounted-on)
> > directory. It may, or may not, also return filehandle information.
> >
> > If this happens, and the lookup in nfs_prime_dcache() returns the
> > dentry for the submounted directory, the filehandle comparison will
> > fail, and we call d_invalidate(). Post-commit 8ed936b5671bf
> > ("vfs: Lazily remove mounts on unlinked files and directories."), this
> > means the entire subtree is unmounted.
> >
> > The following minimal patch addresses this problem by punting on
> > the invalidation if there is a submount.
> >
> > Kudos to Neil Brown <neilb@suse.de> for having tracked down this
> > issue (see link).
> >
> > Reported-by: Nix <nix@esperi.org.uk>
> > Link: http://lkml.kernel.org/r/87iofju9ht.fsf@spindle.srvr.nix
> > Cc: stable@vger.kernel.org # 3.18+
> > Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> > ---
> >  fs/nfs/dir.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> > index 9b0c55cb2a2e..0da617a61c0b 100644
> > --- a/fs/nfs/dir.c
> > +++ b/fs/nfs/dir.c
> > @@ -479,6 +479,10 @@ void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
> >
> >         dentry = d_lookup(parent, &filename);
> >         if (dentry != NULL) {
> > +               /* Is there a mountpoint here? If so, just exit */
> > +               if (!nfs_fsid_equal(&NFS_SB(dentry->d_sb)->fsid,
> > +                                       &entry->fattr->fsid))
> > +                       goto out;
> >                 if (nfs_same_file(dentry, entry)) {
> >                         nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
> >                         status = nfs_refresh_inode(dentry->d_inode, entry->fattr);
> > --
> 
> ...and this of course needs the test for NFS_ATTR_FATTR_FSID from
> 3/3.... I've updated.
> 
> 
> 

Sorry ... I didn't see this before my earlier reply...

What exactly do you do if NFS_ATTR_FATTR_FSID isn't set?
Hopefully you "goto out".

Thanks,
NeilBrown

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