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>

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 44523f4a6084..6faaf710e563 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -154,6 +154,7 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 	struct dnotify_struct *dn;
 	struct dnotify_struct **prev;
 	struct inode *inode;
+	bool free = false;
 
 	inode = file_inode(filp);
 	if (!S_ISDIR(inode->i_mode))
@@ -182,11 +183,15 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 
 	/* nothing else could have found us thanks to the dnotify_groups
 	   mark_mutex */
-	if (dn_mark->dn == NULL)
-		fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
+	if (dn_mark->dn == NULL) {
+		fsnotify_detach_mark(fsn_mark);
+		free = true;
+	}
 
 	mutex_unlock(&dnotify_group->mark_mutex);
 
+	if (free)
+		fsnotify_free_mark(fsn_mark);
 	fsnotify_put_mark(fsn_mark);
 }
 
@@ -362,9 +367,10 @@ out:
 	spin_unlock(&fsn_mark->lock);
 
 	if (destroy)
-		fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
-
+		fsnotify_detach_mark(fsn_mark);
 	mutex_unlock(&dnotify_group->mark_mutex);
+	if (destroy)
+		fsnotify_free_mark(fsn_mark);
 	fsnotify_put_mark(fsn_mark);
 out_err:
 	if (new_fsn_mark)