btrfs: print leaked references in kill_all_delayed_nodes()

We are seeing soft lockups in kill_all_delayed_nodes due to a
delayed_node with a lingering reference count of 1. Printing at this
point will reveal the guilty stack trace. If the delayed_node has no
references there should be no output.

Signed-off-by: Leo Martins <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: loemraw

fs/btrfs/delayed-inode.c

@@ -2115,6 +2115,7 @@ void btrfs_kill_all_delayed_nodes(struct btrfs_root *root)
 			__btrfs_kill_delayed_node(delayed_nodes[i]);
 			btrfs_release_delayed_node(delayed_nodes[i],
 						   &delayed_node_trackers[i]);
+			btrfs_delayed_node_ref_tracker_dir_print(delayed_nodes[i]);
 		}
 	}
 }

fs/btrfs/delayed-inode.h

@@ -208,6 +208,12 @@ static inline void btrfs_delayed_node_ref_tracker_dir_exit(struct btrfs_delayed_
 	ref_tracker_dir_exit(&node->ref_dir.dir);
 }
 
+static inline void btrfs_delayed_node_ref_tracker_dir_print(struct btrfs_delayed_node *node)
+{
+	ref_tracker_dir_print(&node->ref_dir.dir,
+			      BTRFS_DELAYED_NODE_REF_TRACKER_DISPLAY_LIMIT);
+}
+
 static inline int btrfs_delayed_node_ref_tracker_alloc(struct btrfs_delayed_node *node,
 						       struct btrfs_ref_tracker *tracker,
 						       gfp_t gfp)
@@ -225,6 +231,8 @@ static inline void btrfs_delayed_node_ref_tracker_dir_init(struct btrfs_delayed_
 
 static inline void btrfs_delayed_node_ref_tracker_dir_exit(struct btrfs_delayed_node *node) { }
 
+static inline void btrfs_delayed_node_ref_tracker_dir_print(struct btrfs_delayed_node *node) { }
+
 static inline int btrfs_delayed_node_ref_tracker_alloc(struct btrfs_delayed_node *node,
 						       struct btrfs_ref_tracker *tracker,
 						       gfp_t gfp)