---

yaml
---
r: 347031
b: refs/heads/master
c: ebe945c
h: refs/heads/master
i:
  347029: 828771a
  347027: 8b37aed
  347023: e4e9568
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 92e793495597af4135d94314113bf13eafb0e663
+refs/heads/master: ebe945c27628fca03723582eba138acc2e2f3d15

trunk/include/linux/memcontrol.h

@@ -422,6 +422,12 @@ static inline void sock_release_memcg(struct sock *sk)
 extern struct static_key memcg_kmem_enabled_key;
 
 extern int memcg_limited_groups_array_size;
+
+/*
+ * Helper macro to loop through all memcg-specific caches. Callers must still
+ * check if the cache is valid (it is either valid or NULL).
+ * the slab_mutex must be held when looping through those caches
+ */
 #define for_each_memcg_cache_index(_idx)	\
 	for ((_idx) = 0; i < memcg_limited_groups_array_size; (_idx)++)
 

trunk/mm/slab.c

@@ -4099,6 +4099,7 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
 	if ((ret < 0) || !is_root_cache(cachep))
 		return ret;
 
+	VM_BUG_ON(!mutex_is_locked(&slab_mutex));
 	for_each_memcg_cache_index(i) {
 		c = cache_from_memcg(cachep, i);
 		if (c)

trunk/mm/slub.c

@@ -5108,12 +5108,25 @@ static ssize_t slab_attr_store(struct kobject *kobj,
 		if (s->max_attr_size < len)
 			s->max_attr_size = len;
 
+		/*
+		 * This is a best effort propagation, so this function's return
+		 * value will be determined by the parent cache only. This is
+		 * basically because not all attributes will have a well
+		 * defined semantics for rollbacks - most of the actions will
+		 * have permanent effects.
+		 *
+		 * Returning the error value of any of the children that fail
+		 * is not 100 % defined, in the sense that users seeing the
+		 * error code won't be able to know anything about the state of
+		 * the cache.
+		 *
+		 * Only returning the error code for the parent cache at least
+		 * has well defined semantics. The cache being written to
+		 * directly either failed or succeeded, in which case we loop
+		 * through the descendants with best-effort propagation.
+		 */
 		for_each_memcg_cache_index(i) {
 			struct kmem_cache *c = cache_from_memcg(s, i);
-			/*
-			 * This function's return value is determined by the
-			 * parent cache only
-			 */
 			if (c)
 				attribute->store(c, buf, len);
 		}