nfsd: move blocked lock handling under a dedicated spinlock

Bruce was hitting some lockdep warnings in testing, showing that we
could hit a deadlock with the new CB_NOTIFY_LOCK handling, involving a
rather complex situation involving four different spinlocks.

The crux of the matter is that we end up taking the nn->client_lock in
the lm_notify handler. The simplest fix is to just declare a new
per-nfsd_net spinlock to protect the new CB_NOTIFY_LOCK structures.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index b10d557f9c9e..ee36efd5aece 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -84,6 +84,8 @@ struct nfsd_net {
 	struct list_head client_lru;
 	struct list_head close_lru;
 	struct list_head del_recall_lru;
+
+	/* protected by blocked_locks_lock */
 	struct list_head blocked_locks_lru;
 
 	struct delayed_work laundromat_work;
@@ -91,6 +93,9 @@ struct nfsd_net {
 	/* client_lock protects the client lru list and session hash table */
 	spinlock_t client_lock;
 
+	/* protects blocked_locks_lru */
+	spinlock_t blocked_locks_lock;
+
 	struct file *rec_file;
 	bool in_grace;
 	const struct nfsd4_client_tracking_ops *client_tracking_ops;