linux-kernel - Re: Error mounting FC8 NFS server with 2.6.31-rc3 NFSv4 client.

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Date:	Wed, 22 Jul 2009 17:32:25 -0400
From:	Andy Adamson <andros@...app.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Ben Greear <greearb@...delatech.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-nfs@...r.kernel.org
Subject: Re: Error mounting FC8 NFS server with 2.6.31-rc3 NFSv4 client.

On Jul 22, 2009, at 4:20 PM, Trond Myklebust wrote:

> On Wed, 2009-07-22 at 15:49 -0400, Andy Adamson wrote:
>> On Jul 21, 2009, at 5:17 PM, Trond Myklebust wrote:
>>> Note that there is a bug remaining inside nfs4_init_session(): we
>>> shouldn't be copying the rsize/wsize into the nfs_client if the  
>>> latter
>>> was already initialised.
>>
>> The rsize/wsize is copied into the session prior to the  
>> create_session
>> call (triggered by the state management code you moved), and is used
>> for session negotiation. At this point the nfs_client cl_cons_state  
>> is
>> set to NFS_CS_SESSION_INITING (see nfs4_alloc_session), so the
>> nfs_client is not initialized.  The cl_cons_state is set to
>> NFS_CS_READY after a successful create_session call.
>
> The call to nfs4_init_session() is in nfs4_create_server(). It can be
> called several times _after_ the nfs_client has been initialised when
> you mount more than one partition from the same NFS server.
>
> If that is the case, and if you use different rsize/wsize values on
> those different mounts, then you will end up clobbering the values of
> fc_attrs.max_rqst_sz, and fc_attrs.max_resp_sz, having set them to the
> wsize/rsize that was set by the very last mount call.

You are right, this is a bug.

>
>
> AFAICS, what you _should_ be doing in nfs4_init_session, is something
> like
>
> 	if (clp->cl_session->fc_attrs.max_rqst_sz < server->wsize)
> 		clp->cl_session->fc_attrs.max_rqst_sz = server->wsize;

Currently, we only support one session per  nfs_client -  one session  
for all partition mounts to the same NFS server.
For NFSv4.1 the per partition struct nfs_server rsize/wsize is used to  
construct rpc requests that are sent over the session so the rsize/ 
wsize must not be larger than the session max_resp_sz/max_rqst_sz.

nfs4_init_session should simply return if the nfs_client cl_cons_state  
is not NFS_CS_SESSION_INITING.
I shouldn't be trying to set the session max_resp_sz/max_rqst_sz to  
the rsize/wsize, but rather to the maximum rsize/wsize supported by  
the client.
If the server accepts or increases the max_resp_sz/max_rqst_sz then  
all is well.
If the server reduces the max_resp_sz/max_rqst_sz, the maximum rsize/ 
wsize available for NFSv4.1 partition mounts to the server needs to be  
reduced accordingly. So the nfs_server rsize/wsize needs to be bound  
by the session max_resp_sz/max_rqst_sz as well as by the maximum  
supported size.

If you think this is correct, I'll send a patch.

-->Andy

>
>
> Trond
>

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