Re: NFSv4 cannot unmount ESTALE directories (in some cases).

["dE ." <de.techno@gmail.com>]

On 01/21/13 08:39, Al Viro wrote:
> On Mon, Jan 21, 2013 at 01:48:59PM +1100, NeilBrown wrote:
>> If you use NFSv4 to "mount server:/foo/bar /mnt", then "rm -r" /foo/bar on the
>> server, then accesses to /mnt will naturally return ESTALE.
>>
>> Unfortunately "umount /mnt" will also return ESTALE and leave the stale
>> directory mounted.  Adding "-l" or "-f" to "umount" doesn't help.
>>
>> The problem is that nfs_lookup_revalidate fails.  As the mountpoint is never
>> not accessed by a lookup (after the initial mount) it seems a bit pointless
>> calling d_revalidate in this case ... by maybe not.
>>
>> I can make the problem go away by testing for LOOKUP_JUMP and having
>> nfs_lookup_revalidate never fail if that flag it set (for a directory).
>> However I cannot easily tell if this is an elegant solution of an ugly hack,
> The latter.  Definitely.
>
>> and am hoping that someone who understands revalidation and LOOKUP_JUMPED
>> better than I (who only discovered the latter today) could provide advice.
>>
>> Al?  Trond?  Should  I make this into a formal patch submission, or is there
>> a better way?
> I really suspect that mountpoint crossing on umount ought to be done
> differently.  I'll need to play with possible variants a bit before I can
> offer any replacement though...
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I'm affected. I've to do exportfs -f to fix the issue. This problem only 
persists with loop mounts.