[PATCH v3 1/2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB

From: Thomas Garnier
Date: Mon Nov 07 2016 - 16:42:30 EST

From: Greg Thelen <gthelen@xxxxxxxxxx>

While testing OBJFREELIST_SLAB integration with pagealloc, we found a
bug where kmem_cache(sys) would be created with both CFLGS_OFF_SLAB &

The original kmem_cache is created early making OFF_SLAB not possible.
When kmem_cache(sys) is created, OFF_SLAB is possible and if pagealloc
is enabled it will try to enable it first under certain conditions.
Given kmem_cache(sys) reuses the original flag, you can have both flags
at the same time resulting in allocation failures and odd behaviors.

This fix discards allocator specific flags from memcg before calling

Fixes: b03a017bebc4 ("mm/slab: introduce new slab management type, OBJFREELIST_SLAB")
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
Tested-by: Thomas Garnier <thgarnie@xxxxxxxxxx>
Based on next-20161027
mm/slab_common.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 71f0b28..329b038 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -533,8 +533,8 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,

s = create_cache(cache_name, root_cache->object_size,
root_cache->size, root_cache->align,
- root_cache->flags, root_cache->ctor,
- memcg, root_cache);
+ root_cache->flags & CACHE_CREATE_MASK,
+ root_cache->ctor, memcg, root_cache);
* If we could not create a memcg cache, do not complain, because
* that's not critical at all as we can always proceed with the root