fsnotify: duplicate fsnotify_mark_entry data between 2 marks

Simple copy fsnotify information from one mark to another in preparation
for the second mark to replace the first.
Signed-off-by: NEric Paris <eparis@redhat.com>

fs/notify/inode_mark.c

@@ -282,12 +282,20 @@ struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *grou
 	return NULL;
 }
 
+void fsnotify_duplicate_mark(struct fsnotify_mark_entry *new, struct fsnotify_mark_entry *old)
+{
+	assert_spin_locked(&old->lock);
+	new->inode = old->inode;
+	new->group = old->group;
+	new->mask = old->mask;
+	new->free_mark = old->free_mark;
+}
+
 /*
  * Nothing fancy, just initialize lists and locks and counters.
  */
 void fsnotify_init_mark(struct fsnotify_mark_entry *entry,
 			void (*free_mark)(struct fsnotify_mark_entry *entry))
-
 {
 	spin_lock_init(&entry->lock);
 	atomic_set(&entry->refcnt, 1);

include/linux/fsnotify_backend.h

@@ -342,6 +342,8 @@ extern void fsnotify_recalc_inode_mask(struct inode *inode);
 extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
 /* find (and take a reference) to a mark associated with group and inode */
 extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
+/* copy the values from old into new */
+extern void fsnotify_duplicate_mark(struct fsnotify_mark_entry *new, struct fsnotify_mark_entry *old);
 /* attach the mark to both the group and the inode */
 extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
 /* given a mark, flag it to be freed when all references are dropped */