Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754990AbcJZRlk (ORCPT ); Wed, 26 Oct 2016 13:41:40 -0400 Received: from mail-pf0-f176.google.com ([209.85.192.176]:33772 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932334AbcJZRli (ORCPT ); Wed, 26 Oct 2016 13:41:38 -0400 From: Thomas Garnier To: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, gthelen@google.com, Thomas Garnier Subject: [PATCH v1] memcg: Prevent caches to be both OFF_SLAB & OBJFREELIST_SLAB Date: Wed, 26 Oct 2016 10:41:28 -0700 Message-Id: <1477503688-69191-1-git-send-email-thgarnie@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1624 Lines: 44 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. 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. The proposed fix removes these flags by default at the entrance of __kmem_cache_create. This way the function will define which way the freelist should be handled at this stage for the new cache. Fixes: b03a017bebc4 ("mm/slab: introduce new slab management type, OBJFREELIST_SLAB") Signed-off-by: Thomas Garnier Signed-off-by: Greg Thelen --- Based on next-20161025 --- mm/slab.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/slab.c b/mm/slab.c index 3c83c29..efe280a 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2027,6 +2027,14 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) int err; size_t size = cachep->size; + /* + * memcg re-creates caches with the flags of the originals. Remove + * the freelist related flags to ensure they are re-defined at this + * stage. Prevent having both flags on edge cases like with pagealloc + * if the original cache was created too early to be OFF_SLAB. + */ + flags &= ~(CFLGS_OBJFREELIST_SLAB|CFLGS_OFF_SLAB); + #if DEBUG #if FORCED_DEBUG /* -- 2.8.0.rc3.226.g39d4020