[PATCH 2/4] NFS: replace per-net client lock by mutex

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
creation, which can be called on mount notification, where this per-net client
lock is taken on clients list walk.

Note: I used simple mutex instead of rw semaphore because of
nfs_put_client->atomic_dec_and_mutex_lock() call. Probably, there is a better
solution here.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

---
 fs/nfs/client.c |   36 ++++++++++++++++++------------------
 fs/nfs/idmap.c  |    4 ++--
 fs/nfs/netns.h  |    2 +-
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8563585..d15269f 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -72,9 +72,9 @@ static int nfs_get_cb_ident_idr(struct nfs_client *clp, int minorversion)
 retry:
 	if (!idr_pre_get(&nn->cb_ident_idr, GFP_KERNEL))
 		return -ENOMEM;
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	ret = idr_get_new(&nn->cb_ident_idr, clp, &clp->cl_cb_ident);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	if (ret == -EAGAIN)
 		goto retry;
 	return ret;
@@ -321,10 +321,10 @@ void nfs_put_client(struct nfs_client *clp)
 	dprintk("--> nfs_put_client({%d})\n", atomic_read(&clp->cl_count));
 	nn = net_generic(clp->net, nfs_net_id);
 
-	if (atomic_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) {
+	if (atomic_dec_and_mutex_lock(&clp->cl_count, &nn->nfs_client_lock)) {
 		list_del(&clp->cl_share_link);
 		nfs_cb_idr_remove_locked(clp);
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 
 		BUG_ON(!list_empty(&clp->cl_superblocks));
 
@@ -519,7 +519,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 
 	/* see if the client already exists */
 	do {
-		spin_lock(&nn->nfs_client_lock);
+		mutex_lock(&nn->nfs_client_lock);
 
 		clp = nfs_match_client(cl_init);
 		if (clp)
@@ -527,7 +527,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 		if (new)
 			goto install_client;
 
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 
 		new = nfs_alloc_client(cl_init);
 	} while (!IS_ERR(new));
@@ -539,7 +539,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 install_client:
 	clp = new;
 	list_add(&clp->cl_share_link, &nn->nfs_client_list);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	error = cl_init->rpc_ops->init_client(clp, timeparms, ip_addr,
 					      authflavour, noresvport);
@@ -554,7 +554,7 @@ install_client:
 	 * - make sure it's ready before returning
 	 */
 found_client:
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	if (new)
 		nfs_free_client(new);
@@ -1045,11 +1045,11 @@ 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(&nn->nfs_client_lock);
+	mutex_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(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 }
 
@@ -1061,12 +1061,12 @@ static void nfs_server_remove_lists(struct nfs_server *server)
 	if (clp == NULL)
 		return;
 	nn = net_generic(clp->net, nfs_net_id);
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_del_rcu(&server->client_link);
 	if (list_empty(&clp->cl_superblocks))
 		set_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
 	list_del(&server->master_link);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	synchronize_rcu();
 }
@@ -1220,11 +1220,11 @@ nfs4_find_client_ident(struct net *net, int cb_ident)
 	struct nfs_client *clp;
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	clp = idr_find(&nn->cb_ident_idr, cb_ident);
 	if (clp)
 		atomic_inc(&clp->cl_count);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return clp;
 }
 
@@ -1243,7 +1243,7 @@ nfs4_find_client_sessionid(struct net *net, const struct sockaddr *addr,
 	struct nfs_client *clp;
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
 		if (nfs4_cb_match_client(addr, clp, 1) == false)
 			continue;
@@ -1257,10 +1257,10 @@ nfs4_find_client_sessionid(struct net *net, const struct sockaddr *addr,
 			continue;
 
 		atomic_inc(&clp->cl_count);
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 		return clp;
 	}
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return NULL;
 }
 
@@ -1781,7 +1781,7 @@ 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);
+	mutex_init(&nn->nfs_client_lock);
 }
 
 #ifdef CONFIG_PROC_FS
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b5c6d8e..98b0b6b 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -561,7 +561,7 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 	struct nfs_client *clp;
 	int error = 0;
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_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;
@@ -569,7 +569,7 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 		if (error)
 			break;
 	}
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return error;
 }
 
diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h
index 7baad89..24d0bc3 100644
--- a/fs/nfs/netns.h
+++ b/fs/nfs/netns.h
@@ -12,7 +12,7 @@ struct nfs_net {
 #ifdef CONFIG_NFS_V4
 	struct idr cb_ident_idr; /* Protected by nfs_client_lock */
 #endif
-	spinlock_t nfs_client_lock;
+	struct mutex nfs_client_lock;
 };
 
 extern int nfs_net_id;