From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932613Ab2IDRYu (ORCPT ); Tue, 4 Sep 2012 13:24:50 -0400 Received: from cantor2.suse.de ([195.135.220.15]:42940 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757463Ab2IDRYn (ORCPT ); Tue, 4 Sep 2012 13:24:43 -0400 From: Mel Gorman To: Andrew Morton Cc: Linux-MM , Linux-Netdev , LKML , David Miller , Chuck Lever , Joonsoo Kim , Pekka@suse.de, "Enberg , Mel Gorman Subject: [PATCH 1/4] slab: do ClearSlabPfmemalloc() for all pages of slab Date: Tue, 4 Sep 2012 18:24:36 +0100 Message-Id: <1346779479-1097-2-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.9.2 In-Reply-To: <1346779479-1097-1-git-send-email-mgorman@suse.de> References: <1346779479-1097-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Right now, we call ClearSlabPfmemalloc() for first page of slab when we clear SlabPfmemalloc flag. This is fine for most swap-over-network use cases as it is expected that order-0 pages are in use. Unfortunately it is possible that that __ac_put_obj() checks SlabPfmemalloc on a tail page and while this is harmless, it is sloppy. This patch ensures that the head page is always used. This problem was originally identified by Joonsoo Kim. [js1304@gmail.com: Original implementation and problem identification] Signed-off-by: Mel Gorman --- mm/slab.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 811af03..d34a903 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1000,7 +1000,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac, l3 = cachep->nodelists[numa_mem_id()]; if (!list_empty(&l3->slabs_free) && force_refill) { struct slab *slabp = virt_to_slab(objp); - ClearPageSlabPfmemalloc(virt_to_page(slabp->s_mem)); + ClearPageSlabPfmemalloc(virt_to_head_page(slabp->s_mem)); clear_obj_pfmemalloc(&objp); recheck_pfmemalloc_active(cachep, ac); return objp; @@ -1032,7 +1032,7 @@ static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac, { if (unlikely(pfmemalloc_active)) { /* Some pfmemalloc slabs exist, check if this is one */ - struct page *page = virt_to_page(objp); + struct page *page = virt_to_head_page(objp); if (PageSlabPfmemalloc(page)) set_obj_pfmemalloc(&objp); } -- 1.7.9.2