slub: Acquire_slab() avoid loop

Avoid the loop in acquire slab and simply fail if there is a conflict.

This will cause the next page on the list to be considered.

Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/mm/slub.c b/mm/slub.c
index a3395c2..9892775 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1490,12 +1490,12 @@ static inline void remove_partial(struct kmem_cache_node *n,
 }
 
 /*
- * Lock slab, remove from the partial list and put the object into the
- * per cpu freelist.
+ * Remove slab from the partial list, freeze it and
+ * return the pointer to the freelist.
  *
  * Returns a list of objects or NULL if it fails.
  *
- * Must hold list_lock.
+ * Must hold list_lock since we modify the partial list.
  */
 static inline void *acquire_slab(struct kmem_cache *s,
                struct kmem_cache_node *n, struct page *page,
@@ -1510,22 +1510,24 @@ static inline void *acquire_slab(struct kmem_cache *s,
         * The old freelist is the list of objects for the
         * per cpu allocation list.
         */
-       do {
-               freelist = page->freelist;
-               counters = page->counters;
-               new.counters = counters;
-               if (mode)
-                       new.inuse = page->objects;
+       freelist = page->freelist;
+       counters = page->counters;
+       new.counters = counters;
+       if (mode)
+               new.inuse = page->objects;
 
-               VM_BUG_ON(new.frozen);
-               new.frozen = 1;
+       VM_BUG_ON(new.frozen);
+       new.frozen = 1;
 
-       } while (!__cmpxchg_double_slab(s, page,
+       if (!__cmpxchg_double_slab(s, page,
                        freelist, counters,
                        NULL, new.counters,
-                       "lock and freeze"));
+                       "acquire_slab"))
+
+               return NULL;
 
        remove_partial(n, page);
+       WARN_ON(!freelist);
        return freelist;
 }