NFS: make nfs_client_lock per net ns

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@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 2f78f0c..d2afcd8 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -536,7 +536,7 @@
 	struct nfs_client *clp;
 	int error = 0;
 
-	spin_lock(&nfs_client_lock);
+	spin_lock(&nn->nfs_client_lock);
 	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
@@ -544,7 +544,7 @@
 		if (error)
 			break;
 	}
-	spin_unlock(&nfs_client_lock);
+	spin_unlock(&nn->nfs_client_lock);
 	return error;
 }