netdev - Re: [PATCH 4/4] NFS: make nfs_client

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Date:	Tue, 7 Feb 2012 13:51:00 +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>,
	"xemul@...allels.com" <xemul@...allels.com>,
	"neilb@...e.de" <neilb@...e.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jbottomley@...allels.com" <jbottomley@...allels.com>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH 4/4] NFS: make nfs_client_lock per net ns

On Mon, 2012-01-23 at 17:26 +0000, Stanislav Kinsbursky wrote:
> This patch makes nfs_clients_lock allocated per network namespace. All items it
> protects are already network namespace aware.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> 
> ---
>  fs/nfs/client.c   |   51 +++++++++++++++++++++++++++++----------------------
>  fs/nfs/idmap.c    |    4 ++--
>  fs/nfs/internal.h |    3 ---
>  fs/nfs/netns.h    |    1 +
>  4 files changed, 32 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index f51b279..9e11d29 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -551,7 +553,7 @@ install_client:
>  	 * - make sure it's ready before returning
>  	 */
>  found_client:
> -	spin_unlock(&nfs_client_lock);
> +	spin_unlock(&nn->nfs_client_lock);
>  
>  	if (new)
>  		nfs_free_client(new);
> @@ -1041,24 +1043,25 @@ static void nfs_server_insert_lists(struct nfs_server *server)
>  	struct nfs_client *clp = server->nfs_client;
>  	struct nfs_net *nn = net_generic(clp->net, nfs_net_id);
>  
> -	spin_lock(&nfs_client_lock);
> +	spin_lock(&nn->nfs_client_lock);
>  	list_add_tail_rcu(&server->client_link, &clp->cl_superblocks);
>  	list_add_tail(&server->master_link, &nn->nfs_volume_list);
>  	clear_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
> -	spin_unlock(&nfs_client_lock);
> +	spin_unlock(&nn->nfs_client_lock);
>  
>  }
>  
>  static void nfs_server_remove_lists(struct nfs_server *server)
>  {
>  	struct nfs_client *clp = server->nfs_client;
> +	struct nfs_net *nn = net_generic(clp->net, nfs_net_id);
>  
> -	spin_lock(&nfs_client_lock);
> +	spin_lock(&nn->nfs_client_lock);
>  	list_del_rcu(&server->client_link);
>  	if (clp && list_empty(&clp->cl_superblocks))
>  		set_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
>  	list_del(&server->master_link);
> -	spin_unlock(&nfs_client_lock);
> +	spin_unlock(&nn->nfs_client_lock);
>  
>  	synchronize_rcu();
>  }

This hunk causes an Oops when nfs_server_remove_lists gets called from
nfs4_create_server(). I've applied the following patch to fix it up.

Cheers
  Trond
8<-------------------------------------------------------------------------
From 5a489156da4fd15dd143f2b21dd9657b97dcef88 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@...app.com>
Date: Tue, 7 Feb 2012 00:05:11 -0500
Subject: [PATCH] NFS: Initialise the nfs_net->nfs_client_lock

Ensure that we initialise the nfs_net->nfs_client_lock spinlock.
Also ensure that nfs_server_remove_lists() doesn't try to
dereference server->nfs_client before that is initialised.

Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Cc: Stanislav Kinsbursky <skinsbursky@...allels.com>
---
 fs/nfs/client.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 1a5cd49..f0dacad 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1055,8 +1055,11 @@ static void nfs_server_insert_lists(struct nfs_server *server)
 static void nfs_server_remove_lists(struct nfs_server *server)
 {
 	struct nfs_client *clp = server->nfs_client;
-	struct nfs_net *nn = net_generic(clp->net, nfs_net_id);
+	struct nfs_net *nn;
 
+	if (clp == NULL)
+		return;
+	nn = net_generic(clp->net, nfs_net_id);
 	spin_lock(&nn->nfs_client_lock);
 	list_del_rcu(&server->client_link);
 	if (clp && list_empty(&clp->cl_superblocks))
@@ -1777,6 +1780,7 @@ void nfs_clients_init(struct net *net)
 #ifdef CONFIG_NFS_V4
 	idr_init(&nn->cb_ident_idr);
 #endif
+	spin_lock_init(&nn->nfs_client_lock);
 }
 
 #ifdef CONFIG_PROC_FS
-- 
1.7.7.6



-- 
Trond Myklebust
Linux NFS client maintainer

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