On Tue, Sep 25, 2012 at 04:29:58AM -0700, Eric W. Biederman wrote:
> Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx> writes:
>
> >> Could you try the following patch? This should report what directories
> >> cannot be renamed because one of them is a mount point and it gives some
> >> real insight into what is going on.
> >
> > ls /
> > __d_unalias: /dev -> /dev
> > __d_unalias: /proc -> /proc
> > __d_unalias: /sys -> /sys
>
> Ok. That is what I thought was going on. For some reason nfs is
> attempting to recreate an existing dentry.
>
> Does this fix the nfs problem for you?
>
> Eric
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 8086636..6390f0f 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -2404,6 +2404,9 @@ out_unalias:
> if (likely(!d_mountpoint(alias))) {
> __d_move(alias, dentry);
> ret = alias;
> + } else if ((alias->d_parent == dentry->d_parent) &&
> + !dentry_cmp(alias, dentry->d_name.name, dentry->d_name.len))
> + ret = alias;
> }
The interesting question is why the hell had it decided that preexisting
dentry was not good enough for it? Note that we have arrived to nfs_lookup()
after we'd decided *not* to use the damn alias. The trace posted upthread
went __lookup_hash() -> lookup_real(). It means that lookup_dcache()
has not produced this one. And no, even if ->d_revalidate() decided it
was no good, the logics in d_invalidate() would've said "busy" and we'd
gone with that dentry anyway. So it means that d_lookup() has not
found it at all.
IOW, something out there is blindly unhashing mountpoint dentries; that's
where the real root of the problem seems to be. Could you slap
WARN_ON(d_mountpoint(dentry)) in __d_drop() and see what it catches?
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