Commit f773e36d authored by Greg Thelen's avatar Greg Thelen Committed by Linus Torvalds
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memcg: prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB

While testing OBJFREELIST_SLAB integration with pagealloc, we found a
bug where kmem_cache(sys) would be created with both CFLGS_OFF_SLAB &
CFLGS_OBJFREELIST_SLAB.  When it happened, critical allocations needed
for loading drivers or creating new caches will fail.

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

The bug exists since 4.6-rc1 and affects testing debug pagealloc

Fixes: b03a017b ("mm/slab: introduce new slab management type, OBJFREELIST_SLAB")

Signed-off-by: default avatarGreg Thelen <>
Signed-off-by: default avatarThomas Garnier <>
Tested-by: default avatarThomas Garnier <>
Acked-by: default avatarChristoph Lameter <>
Cc: Pekka Enberg <>
Cc: David Rientjes <>
Cc: Joonsoo Kim <>
Cc: Vladimir Davydov <>
Cc: Michal Hocko <>
Cc: Johannes Weiner <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 70d78fe7
......@@ -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
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