locks: move checks from locks_free_lock() to locks_release_private()

Code that allocates locks using locks_alloc_lock() will free it
using locks_free_lock(), and will benefit from the BUG_ON()
consistency checks therein.

However some code (nfsd and lockd) allocate a lock embedded in
some other data structure, and so free the lock themselves after
calling locks_release_private().  This path does not benefit from
the consistency checks.

To help catch future errors, move the BUG_ON() checks to
locks_release_private() - which locks_free_lock() already calls.
This ensures that all users for locks will find out if the lock
isn't detached properly before being free.
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/locks.c

@@ -352,6 +352,12 @@ EXPORT_SYMBOL_GPL(locks_alloc_lock);
 
 void locks_release_private(struct file_lock *fl)
 {
+	BUG_ON(waitqueue_active(&fl->fl_wait));
+	BUG_ON(!list_empty(&fl->fl_list));
+	BUG_ON(!list_empty(&fl->fl_blocked_requests));
+	BUG_ON(!list_empty(&fl->fl_blocked_member));
+	BUG_ON(!hlist_unhashed(&fl->fl_link));
+
 	if (fl->fl_ops) {
 		if (fl->fl_ops->fl_release_private)
 			fl->fl_ops->fl_release_private(fl);
@@ -371,12 +377,6 @@ EXPORT_SYMBOL_GPL(locks_release_private);
 /* Free a lock which is not in use. */
 void locks_free_lock(struct file_lock *fl)
 {
-	BUG_ON(waitqueue_active(&fl->fl_wait));
-	BUG_ON(!list_empty(&fl->fl_list));
-	BUG_ON(!list_empty(&fl->fl_blocked_requests));
-	BUG_ON(!list_empty(&fl->fl_blocked_member));
-	BUG_ON(!hlist_unhashed(&fl->fl_link));
-
 	locks_release_private(fl);
 	kmem_cache_free(filelock_cache, fl);
 }