Re: 2.6.38.6 - state manager constantly respawns

[Harry Edmon <harry@uw.edu>]

On 05/20/11 10:52, Trond Myklebust wrote:
> On Fri, 2011-05-20 at 13:26 -0400, Dr. J. Bruce Fields wrote:
>    
>> On Fri, May 20, 2011 at 09:20:47AM -0700, Harry Edmon wrote:
>>      
>>> On 05/16/11 13:53, Dr. J. Bruce Fields wrote:
>>>        
>>>> Hm, so the renews all have clid 465ccc4d09000000, and the reads all have
>>>> a stateid (0, 465ccc4dc24c0a0000000000).
>>>>
>>>> So the first 4 bytes matching just tells me both were handed out by the
>>>> same server instance (so there was no server reboot in between); there's
>>>> no way for me to tell whether they really belong to the same client.
>>>>
>>>> The server does assume that any stateid from the current server instance
>>>> that no longer exists in its table is expired.  I believe that's
>>>> correct, given a correctly functioning client, but perhaps I'm missing a
>>>> case.
>>>>
>>>> --b.
>>>>          
>>> I am very appreciative of the quick initial comments I receive from
>>> all of you on my NFS problem.   I notice that there has been silence
>>> on the problem since the 16th, so I assume that either this is a
>>> hard bug to track down or you have been busy with higher priority
>>> tasks.  Is there anything I can do to help develop a solution to
>>> this problem?
>>>        
>> Well, the only candidate explanation for the problem is that my
>> assumption--that any time the server gets a stateid from the current
>> boot instance that it doesn't recognize as an active stateid, it is safe
>> for the server to return EXPIRED--is wrong.
>>
>> I don't immediately see why it's wrong, and based on the silence nobody
>> else does either, but I'm not 100% convinced I'm right either.
>>
>> So one approach might be to add server code that makes a better effort
>> to return EXPIRED only when we're sure it's a stateid from an expired
>> client, and see if that solves your problem.
>>
>> Remind me, did you have an easy way to reproduce your problem?
>>      
> My silence is simply because I'm mystified as to how this can happen.
> Patching for it is trivial (see below).
>
> When the server tells us that our lease is expired, the normal behaviour
> for the client is to re-establish the lease, and then proceed to recover
> all known stateids. I don't see how we can 'miss' a stateid that then
> needs to be recovered afterwards...
>
> Cheers
>    Trond
>
> 8<----------------------------------------------------------------------------
>  From 920ddb153f28717be363f6e87dde24ef2a8d0ce2 Mon Sep 17 00:00:00 2001
> From: Trond Myklebust<Trond.Myklebust@netapp.com>
> Date: Fri, 20 May 2011 13:44:02 -0400
> Subject: [PATCH] NFSv4: Handle expired stateids when the lease is still valid
>
> Currently, if the server returns NFS4ERR_EXPIRED in reply to a READ or
> WRITE, but the RENEW test determines that the lease is still active, we
> fail to recover and end up looping forever in a READ/WRITE + RENEW death
> spiral.
>
> Signed-off-by: Trond Myklebust<Trond.Myklebust@netapp.com>
> ---
>   fs/nfs/nfs4proc.c |    9 +++++++--
>   1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index cf1b339..d0e15db 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -267,9 +267,11 @@ static int nfs4_handle_exception(struct nfs_server *server, int errorcode, struc
>   				break;
>   			nfs4_schedule_stateid_recovery(server, state);
>   			goto wait_on_recovery;
> +		case -NFS4ERR_EXPIRED:
> +			if (state != NULL)
> +				nfs4_schedule_stateid_recovery(server, state);
>   		case -NFS4ERR_STALE_STATEID:
>   		case -NFS4ERR_STALE_CLIENTID:
> -		case -NFS4ERR_EXPIRED:
>   			nfs4_schedule_lease_recovery(clp);
>   			goto wait_on_recovery;
>   #if defined(CONFIG_NFS_V4_1)
> @@ -3670,9 +3672,11 @@ nfs4_async_handle_error(struct rpc_task *task, const struct nfs_server *server,
>   				break;
>   			nfs4_schedule_stateid_recovery(server, state);
>   			goto wait_on_recovery;
> +		case -NFS4ERR_EXPIRED:
> +			if (state != NULL)
> +				nfs4_schedule_stateid_recovery(server, state);
>   		case -NFS4ERR_STALE_STATEID:
>   		case -NFS4ERR_STALE_CLIENTID:
> -		case -NFS4ERR_EXPIRED:
>   			nfs4_schedule_lease_recovery(clp);
>   			goto wait_on_recovery;
>   #if defined(CONFIG_NFS_V4_1)
> @@ -4543,6 +4547,7 @@ int nfs4_lock_delegation_recall(struct nfs4_state *state, struct file_lock *fl)
>   			case -ESTALE:
>   				goto out;
>   			case -NFS4ERR_EXPIRED:
> +				nfs4_schedule_stateid_recovery(server, state);
>   			case -NFS4ERR_STALE_CLIENTID:
>   			case -NFS4ERR_STALE_STATEID:
>   				nfs4_schedule_lease_recovery(server->nfs_client);
>    
I installed this patch on my client, and now I am seeing the state 
manager appear in the process accounting file about once a minute rather 
that the constant respawning I saw earlier.  Is once a minute normal, or 
is there still a problem?

-- 
  Dr. Harry Edmon			E-MAIL: harry@uw.edu
  206-543-0547 FAX: 206-543-0308			harry@atmos.washington.edu
  Director of IT, College of the Environment and
  Director of Computing, Dept of Atmospheric Sciences
  University of Washington, Box 351640, Seattle, WA 98195-1640