[PATCH] nfs41: Do not free slot if retried while operation was in progress

[Benny Halevy <bhalevy@panasas.com>]

On Jul. 12, 2010, 22:26 +0300, Trond Myklebust <Trond.Myklebust@netapp.com> wrote:
> On Mon, 2010-07-12 at 22:16 +0300, Benny Halevy wrote:
>> On Jul. 12, 2010, 22:14 +0300, Trond Myklebust <Trond.Myklebust@netapp.com> wrote:
>>> On Mon, 2010-07-12 at 21:58 +0300, Benny Halevy wrote:
>>>> [pnfs@linux-nfs.org -> linux-nfs@vger.kernel.org]
>>>>
>>>> On Jul. 12, 2010, 21:29 +0300, Jim Rees <rees@umich.edu> wrote:
>>>>> Does anyone still care about this?
>>>>>
>>>>>  WARNING: nfs41_sequence_done: Operation in progress slot=1 seq=7 highest_used_slotid=1: please report to pnfs@linux-nfs.org if you saw this message
>>>>
>>>> Heh, need to update hard-coded instructions to point to the new list...
>>>>
>>>>>
>>>>> I'm getting this on the client side of a pnfs block layout mount against the
>>>>> spnfs server.  Kernel is benny's pnfs-all-2.6.35-rc3-2010-07-01 plus EMC
>>>>> complex block layout patches.  It's possible the complex layout code is to
>>>>> blame, but I doubt it because this isn't a complex layout mount.  I can
>>>>> provide more details.
>>>>
>>>> I agree.  This is a generic issue.
>>>> The patch that  adds this check is
>>>> d6ce9ad DEVONLY: nfs41: Do not free slot if retried while operation was in progress
>>>>
>>>> It was originally rejected (http://www.spinics.net/lists/linux-nfs/msg09562.html)
>>>> due to noise regarding where nfs41_sequence_free_slot is called
>>>> but that masked the real issue.
>>>>
>>>> Can you readily reproduce this?
>>>> Can you debug also the server side to see if indeed the client retries the RPC
>>>> while it is in progress on the server?
>>>
>>> So what is the root cause here? Is it the known issue that we don't deal
>>> correctly with an NFS4ERR_DELAY on the SEQUENCE operation?
>>
>> Yes.
> 
> I'm happy to take patches to fix that.
> 
> Trond

>From 7dc3c468463a337dabff7f714a3475e3f51380f6 Mon Sep 17 00:00:00 2001
From: Benny Halevy <bhalevy@panasas.com>
Date: Mon, 12 Jul 2010 22:42:15 +0300
Subject: [PATCH] nfs41: Do not free slot if retried while operation was in progress

Getting NFS4ERR_DELAY on OP_SEQUENCE means that the compound was retried
while it's still in progress on the server.  Therefore its respective
slot must not be freed and reused for other compounds until it either
succeeds or fails with another error status.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
---

That fixed, do we ensure that the client either closes or loses the connection
before retrying?

 fs/nfs/nfs4proc.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 70015dd..baf86b9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -425,6 +425,12 @@ static void nfs41_sequence_done(struct nfs_client *clp,
 		/* Check sequence flags */
 		if (atomic_read(&clp->cl_count) > 1)
 			nfs41_handle_sequence_flag_errors(clp, res->sr_status_flags);
+	} else if (unlikely(res->sr_status == -NFS4ERR_DELAY)) {
+		/* Do not free slot if retried while operation was in progress */
+		tbl = &res->sr_session->fc_slot_table;
+		dprintk("%s: slot=%d seq=%d: Operation in progress\n", __func__,
+			res->sr_slotid, tbl->slots[res->sr_slotid].seq_nr);
+		return;
 	}
 out:
 	/* The session may be reset by one of the error handlers. */