fsnotify: get rid of fsnotify_destroy_mark_locked()

fsnotify_destroy_mark_locked() is subtle to use because it temporarily
releases group->mark_mutex.  To avoid future problems with this
function, split it into two.

fsnotify_detach_mark() is the part that needs group->mark_mutex and
fsnotify_free_mark() is the part that must be called outside of
group->mark_mutex.  This way it's much clearer what's going on and we
also avoid some pointless acquisitions of group->mark_mutex.

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index f044fe3..e0727d7 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -236,6 +236,7 @@
 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED	0x04
 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x08
 #define FSNOTIFY_MARK_FLAG_ALIVE		0x10
+#define FSNOTIFY_MARK_FLAG_ATTACHED		0x20
 	unsigned int flags;		/* flags [mark->lock] */
 	void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 };
@@ -353,8 +354,10 @@
 /* given a group and a mark, flag mark to be freed when all references are dropped */
 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 				  struct fsnotify_group *group);
-extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
-					 struct fsnotify_group *group);
+/* detach mark from inode / mount list, group list, drop inode reference */
+extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
+/* free mark */
+extern void fsnotify_free_mark(struct fsnotify_mark *mark);
 /* run all the marks in a group, and clear all of the vfsmount marks */
 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 /* run all the marks in a group, and clear all of the inode marks */