On 12 Nov 2016, at 7:54, Jeff Layton wrote:
On Sat, 2016-11-12 at 06:08 -0500, Benjamin Coddington wrote:
I've been seeing the following on a modified version of generic/089
that gets the client stuck sending LOCK with NFS4ERR_OLD_STATEID.
1. Client has open stateid A, sends a CLOSE
2. Client sends OPEN with same owner
3. Client sends another OPEN with same owner
4. Client gets a reply to OPEN in 3, stateid is B.2 (stateid B
sequence 2)
5. Client does LOCK,LOCKU,FREE_STATEID from B.2
6. Client gets a reply to CLOSE in 1
7. Client gets reply to OPEN in 2, stateid is B.1
8. Client sends LOCK with B.1 - OLD_STATEID, now stuck in a loop
The CLOSE response in 6 causes us to clear NFS_OPEN_STATE, so that
the OPEN
response in 7 is able to update the open_stateid even though it has a
lower
sequence number.
I think this case could be handled by never updating the open_stateid
if the
stateids match but the sequence number of the new state is less than
the
current open_state.
What kernel is this on?
On v4.9-rc2 with a couple fixups. Without them, I can't test long
enough to
reproduce this race. I don't think any of those are involved in this
problem, though.
Yes, that seems wrong. The client should be picking B.2 for the open
stateid to use. I think that decision of whether to take a seqid is
made
in nfs_need_update_open_stateid. The logic in there looks correct to
me
at first glance though.
nfs_need_update_open_stateid() will return true if NFS_OPEN_STATE is
unset.
That's the precondition set up by steps 1-6. Perhaps it should not
update
the stateid if they match but the sequence number is less, and still set
NFS_OPEN_STATE once more. That will fix _this_ case. Are there other
cases
where that would be a problem?
Ben
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