mm/slub.c: list_lock may not be held in some circumstances

Commit c65c1877bd68 ("slub: use lockdep_assert_held") incorrectly
required that add_full() and remove_full() hold n->list_lock.  The lock
is only taken when kmem_cache_debug(s), since that's the only time it
actually does anything.

Require that the lock only be taken under such a condition.

Reported-by: Larry Finger <[email protected]>
Tested-by: Larry Finger <[email protected]>
Tested-by: Paul E. McKenney <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Signed-off-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/slub.c b/mm/slub.c
index 7e3e0458bce4180d115469b8ce622afef9b1e367..3d3a8a7a0f8c24d19360602dbe08702b4f272bfb 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1004,21 +1004,19 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x)
 static void add_full(struct kmem_cache *s,
        struct kmem_cache_node *n, struct page *page)
 {
-       lockdep_assert_held(&n->list_lock);
-
        if (!(s->flags & SLAB_STORE_USER))
                return;
 
+       lockdep_assert_held(&n->list_lock);
        list_add(&page->lru, &n->full);
 }
 
 static void remove_full(struct kmem_cache *s, struct kmem_cache_node *n, struct page *page)
 {
-       lockdep_assert_held(&n->list_lock);
-
        if (!(s->flags & SLAB_STORE_USER))
                return;
 
+       lockdep_assert_held(&n->list_lock);
        list_del(&page->lru);
 }