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

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Message-Id: <61DE1B95-38CC-4821-BF64-5A6B2EC18538@oracle.com>
Date:	Tue, 22 May 2012 09:47:51 -0400
From:	Chuck Lever <chuck.lever@...cle.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	LKML Kernel <linux-kernel@...r.kernel.org>, devel@...nvz.org
Subject: Re: [PATCH] NFS: init client before declaration


On May 22, 2012, at 8:40 AM, 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 = ...
> 
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>

This patch collides pretty hard with the server trunking detection work.  If you agree this needs to be fixed, the best thing we can do, I guess, is take this patch and drop patch 11, 12, and 13 from my recent patch set, and I'll try to rework for 3.6.

> ---
> fs/nfs/client.c |   22 ++++++++++++----------
> 1 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index ae29d4f..9bf4702 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -525,7 +525,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
> 		cl_init->hostname ?: "", cl_init->rpc_ops->version);
> 
> 	/* see if the client already exists */
> -	do {
> +	while (1) {
> 		spin_lock(&nn->nfs_client_lock);
> 
> 		clp = nfs_match_client(cl_init);
> @@ -537,10 +537,18 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
> 		spin_unlock(&nn->nfs_client_lock);
> 
> 		new = nfs_alloc_client(cl_init);
> -	} while (!IS_ERR(new));
> +		if (IS_ERR(new)) {
> +			dprintk("--> nfs_get_client() = %ld [failed]\n", PTR_ERR(new));
> +			return new;
> +		}
> 
> -	dprintk("--> nfs_get_client() = %ld [failed]\n", PTR_ERR(new));
> -	return new;
> +		error = cl_init->rpc_ops->init_client(new, timeparms, ip_addr,
> +						      authflavour, noresvport);
> +		if (error < 0) {
> +			nfs_put_client(new);
> +			return ERR_PTR(error);
> +		}
> +	}
> 
> 	/* install a new client and return with it unready */
> install_client:
> @@ -548,12 +556,6 @@ install_client:
> 	list_add(&clp->cl_share_link, &nn->nfs_client_list);
> 	spin_unlock(&nn->nfs_client_lock);
> 
> -	error = cl_init->rpc_ops->init_client(clp, timeparms, ip_addr,
> -					      authflavour, noresvport);
> -	if (error < 0) {
> -		nfs_put_client(clp);
> -		return ERR_PTR(error);
> -	}
> 	dprintk("--> nfs_get_client() = %p [new]\n", clp);
> 	return clp;
> 
> 
> --
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-- 
Chuck Lever
chuck[dot]lever[at]oracle[dot]com




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