[PATCH v2 2/4] NFS: release per-net clients lock before calling PipeFS dentries creation

[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.

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

---
 fs/nfs/client.c |    2 +-
 fs/nfs/idmap.c  |    8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8563585..6aeb6b3 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -538,7 +538,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 	/* install a new client and return with it unready */
 install_client:
 	clp = new;
-	list_add(&clp->cl_share_link, &nn->nfs_client_list);
+	list_add_tail(&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,
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b5c6d8e..8a9e7a4 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -558,16 +558,20 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 {
 	struct super_block *sb = ptr;
 	struct nfs_net *nn = net_generic(sb->s_fs_info, nfs_net_id);
-	struct nfs_client *clp;
+	struct nfs_client *clp, *tmp;
 	int error = 0;
 
 	spin_lock(&nn->nfs_client_lock);
-	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
+	list_for_each_entry_safe(clp, tmp, &nn->nfs_client_list, cl_share_link) {
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
+		atomic_inc(&clp->cl_count);
+		spin_unlock(&nn->nfs_client_lock);
 		error = __rpc_pipefs_event(clp, event, sb);
+		nfs_put_client(clp);
 		if (error)
 			break;
+		spin_lock(&nn->nfs_client_lock);
 	}
 	spin_unlock(&nn->nfs_client_lock);
 	return error;