Use list_first_entry in locks_wake_up_blocks

This routine deletes all the elements from the list
with the "while (!list_empty())" loop, and we already
have a list_first_entry() macro to help it look nicer :)
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>

fs/locks.c

@@ -534,7 +534,9 @@ static void locks_insert_block(struct file_lock *blocker,
 static void locks_wake_up_blocks(struct file_lock *blocker)
 {
 	while (!list_empty(&blocker->fl_block)) {
-		struct file_lock *waiter = list_entry(blocker->fl_block.next,
+		struct file_lock *waiter;
+
+		waiter = list_first_entry(&blocker->fl_block,
 				struct file_lock, fl_block);
 		__locks_delete_block(waiter);
 		if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)