Linux-libre 4.3.2-gnu

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index dd3fb0b17..db39de2dd 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -26,7 +26,6 @@
 
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
-#include "../mount.h"
 
 /*
  * Clear all of the marks on an inode when it is being evicted from core
@@ -205,6 +204,16 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 		mnt = NULL;
 
 	/*
+	 * Optimization: srcu_read_lock() has a memory barrier which can
+	 * be expensive.  It protects walking the *_fsnotify_marks lists.
+	 * However, if we do not walk the lists, we do not have to do
+	 * SRCU because we have no references to any objects and do not
+	 * need SRCU to keep them "alive".
+	 */
+	if (hlist_empty(&to_tell->i_fsnotify_marks) &&
+	    (!mnt || hlist_empty(&mnt->mnt_fsnotify_marks)))
+		return 0;
+	/*
 	 * if this is a modify event we may need to clear the ignored masks
 	 * otherwise return if neither the inode nor the vfsmount care about
 	 * this type of event.