Merge v7.1.5linux-rolling-stable

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index e21b2f7f4159..351a5101c862 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -76,20 +76,25 @@ struct kernfs_iattrs;
  * kernfs_open_file.
  *
  * kernfs_open_files are chained at kernfs_open_node->files, which is
- * protected by kernfs_global_locks.open_file_mutex[i].
+ * protected by kernfs_global_locks.node_mutex[i].
  *
  * To reduce possible contention in sysfs access, arising due to single
- * locks, use an array of locks (e.g. open_file_mutex) and use kernfs_node
+ * locks, use an array of locks (e.g. node_mutex) and use kernfs_node
  * object address as hash keys to get the index of these locks.
  *
  * Hashed mutexes are safe to use here because operations using these don't
  * rely on global exclusion.
  *
+ * The hashed mutex array protects per-node data: the kernfs_open_node for
+ * open file management, and kernfs_node xattr operations (necessary because
+ * multiple superblocks with different namespaces can share the same
+ * kernfs_node, making per-inode locking insufficient).
+ *
  * In future we intend to replace other global locks with hashed ones as well.
  * kernfs_global_locks acts as a holder for all such hash tables.
  */
 struct kernfs_global_locks {
-	struct mutex open_file_mutex[NR_KERNFS_LOCKS];
+	struct mutex node_mutex[NR_KERNFS_LOCKS];
 };
 
 enum kernfs_node_type {