Hello,
On Mon, Apr 11, 2016 at 10:20 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> At Connectathon 2016, we found that recent upstream Linux clients
> would occasionally send a LOCK operation with a zero stateid. This
> appeared to happen in close proximity to another thread returning
> a delegation before unlinking the same file while it remained open.
>
> Earlier, the client received a write delegation on this file and
> returned the open stateid. Now, as it is getting ready to unlink the
> file, it returns the write delegation. But there is still an open
> file descriptor on that file, so the client must OPEN the file
> again before it returns the delegation.
>
> Since commit 24311f884189 ('NFSv4: Recovery of recalled read
> delegations is broken'), nfs_open_delegation_recall() clears the
> NFS_DELEGATED_STATE flag _before_ it sends the OPEN. This allows a
> racing LOCK on the same inode to be put on the wire before the OPEN
> operation has returned a valid open stateid.
>
> To eliminate this race, serialize delegation return with the
> acquisition of a file lock on the same file. Adopt the same approach
> as is used in the unlock path.
>
> Fixes: 24311f884189 ('NFSv4: Recovery of recalled read ... ')
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Is it something which is going to be merged in v4.7?
It also might be a good candidate for stable?
Best regards,
--
William
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