slub: fix memcg_propagate_slab_attrs

After creating a cache for a memcg we should initialize its sysfs attrs
with the values from its parent.  That's what memcg_propagate_slab_attrs
is for.  Currently it's broken - we clearly muddled root-vs-memcg caches
there.  Let's fix it up.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 5e234f1f8853..042a47b4d0f5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5071,15 +5071,18 @@ static void memcg_propagate_slab_attrs(struct kmem_cache *s)
 #ifdef CONFIG_MEMCG_KMEM
         int i;
         char *buffer = NULL;
+        struct kmem_cache *root_cache;
 
-        if (!is_root_cache(s))
+        if (is_root_cache(s))
                 return;
 
+        root_cache = s->memcg_params->root_cache;
+
         /*
          * This mean this cache had no attribute written. Therefore, no point
          * in copying default values around
          */
-        if (!s->max_attr_size)
+        if (!root_cache->max_attr_size)
                 return;
 
         for (i = 0; i < ARRAY_SIZE(slab_attrs); i++) {
@@ -5101,7 +5104,7 @@ static void memcg_propagate_slab_attrs(struct kmem_cache *s)
                  */
                 if (buffer)
                         buf = buffer;
-                else if (s->max_attr_size < ARRAY_SIZE(mbuf))
+                else if (root_cache->max_attr_size < ARRAY_SIZE(mbuf))
                         buf = mbuf;
                 else {
                         buffer = (char *) get_zeroed_page(GFP_KERNEL);
@@ -5110,7 +5113,7 @@ static void memcg_propagate_slab_attrs(struct kmem_cache *s)
                         buf = buffer;
                 }
 
-                attr->show(s->memcg_params->root_cache, buf);
+                attr->show(root_cache, buf);
                 attr->store(s, buf, strlen(buf));
         }