On Mon, 14 Jan 2013 14:24:58 -0500
Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Mon, 14 Jan 2013 16:50:20 +0100
> Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> > On Mon, Jan 14, 2013 at 3:54 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > > We've had several reports of this warning over the last year or so:
> > >
> > > [34011.669912] ------------[ cut here ]------------
> > > [34011.670473] WARNING: at fs/dcache.c:2630 prepend_path+0x1eb/0x200()
> > > [34011.671198] Hardware name: Bochs
> > > [34011.671564] Root dentry has weird name <> vfsmnt: fs:nfs4
> >
> > [...]
> >
> > > I'm able to reproduce this warning at will by mounting up a NFS
> > > filesystem, cd'ing into it. If I then lazy unmount the fs and then stat
> > > /proc/pid/cwd for the process sitting in the detached mount, this
> > > warning will fire.
> > >
> > > Given that this is fairly easy to reproduce without doing anything too
> > > exotic, I don't see much value in keeping this warning around.
> >
> > The value of the warning is in preventing filesystems from doing weird
> > and exotic things without thinking about it.
> >
> > The obvious question here is what is NFS4 doing differently from other
> > filesystems to trigger this warning and why.
> >
> > Thanks,
> > Miklos
> >
> > >
> > > Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > ---
> > > fs/dcache.c | 9 ---------
> > > 1 file changed, 9 deletions(-)
> > >
> > > diff --git a/fs/dcache.c b/fs/dcache.c
> > > index 19153a0..08a10a7 100644
> > > --- a/fs/dcache.c
> > > +++ b/fs/dcache.c
> > > @@ -2587,15 +2587,6 @@ out:
> > > return error;
> > >
> > > global_root:
> > > - /*
> > > - * Filesystems needing to implement special "root names"
> > > - * should do so with ->d_dname()
> > > - */
> > > - if (IS_ROOT(dentry) &&
> > > - (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
> > > - WARN(1, "Root dentry has weird name <%.*s>\n",
> > > - (int) dentry->d_name.len, dentry->d_name.name);
> > > - }
> > > if (!slash)
> > > error = prepend(buffer, buflen, "/", 1);
> > > if (!error)
> > > --
> > > 1.7.11.7
> > >
>
> In 3.7-ish kernels, the mnt_root of a NFSv4 mount pointed to a dentry
> with a zero-length name. In 3.8-ish kernels that has changed -- the
> dentry is called '/'. So yeah, it looks like this patch isn't
> necessary.
>
> The question at this point is why and how that changed. I'm guessing
> I'll have to bisect that down to figure it out. Stay tuned...
>
> Thanks,
Ok, found it:
commit b911a6bdeef5848c468597d040e3407e0aee04ce
Author: NeilBrown <neilb@xxxxxxx>
Date: Thu Nov 8 16:09:37 2012 -0800
vfs: d_obtain_alias() needs to use "/" as default name.
Looks like Neil Brown already fixed this the right way. My patch can be
dropped. Sorry for the noise...
Thanks,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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