linux-kernel - Re: [PATCH] NFS: init client before declaration

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Message-ID: <1337696984.4269.4.camel@lade.trondhjem.org>
Date:	Tue, 22 May 2012 14:29:44 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
CC:	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH] NFS: init client before declaration

On Tue, 2012-05-22 at 16:40 +0400, Stanislav Kinsbursky wrote:
> Client have to be initialized prior to adding it to per-net clients list,
> because otherwise there are races, shown below:
> 
> CPU#0					CPU#1
> _____					_____
> 
> nfs_get_client
> nfs_alloc_client
> list_add(..., nfs_client_list)
> 					rpc_fill_super
> 					rpc_pipefs_event
> 					nfs_get_client_for_event
> 					__rpc_pipefs_event
> 					(clp->cl_rpcclient is uninitialized)
> 					BUG()
> init_client
> clp->cl_rpcclient = ...
> 

Why not simply change nfs_get_client_for_event() so that it doesn't
touch nfs_clients that have clp->cl_cons_state!=NFS_CS_READY?

That should ensure that it doesn't touch nfs_clients that failed to
initialise and/or are still in the process of being initialised.

Cheers
  Trond

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com