From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752049AbdATKi7 (ORCPT ); Fri, 20 Jan 2017 05:38:59 -0500 Received: from mx2.suse.de ([195.135.220.15]:36293 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751598AbdATKi4 (ORCPT ); Fri, 20 Jan 2017 05:38:56 -0500 From: Vlastimil Babka To: Andrew Morton Cc: Mel Gorman , Michal Hocko , Hillf Danton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , stable@vger.kernel.org Subject: [PATCH v2 2/4] mm, page_alloc: fix fast-path race with cpuset update or removal Date: Fri, 20 Jan 2017 11:38:41 +0100 Message-Id: <20170120103843.24587-3-vbabka@suse.cz> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170120103843.24587-1-vbabka@suse.cz> References: <20170120103843.24587-1-vbabka@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode triggers OOM killer in few seconds, despite lots of free memory. The test attempts to repeatedly fault in memory in one process in a cpuset, while changing allowed nodes of the cpuset between 0 and 1 in another process. One possible cause is that in the fast path we find the preferred zoneref according to current mems_allowed, so that it points to the middle of the zonelist, skipping e.g. zones of node 1 completely. If the mems_allowed is updated to contain only node 1, we never reach it in the zonelist, and trigger OOM before checking the cpuset_mems_cookie. This patch fixes the particular case by redoing the preferred zoneref search if we switch back to the original nodemask. The condition is also slightly changed so that when the last non-root cpuset is removed, we don't miss it. Note that this is not a full fix, and more patches will follow. Reported-by: Ganapatrao Kulkarni Fixes: 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator") Signed-off-by: Vlastimil Babka Cc: Acked-by: Michal Hocko Acked-by: Mel Gorman --- mm/page_alloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0d771f3fb835..3ca0c15deca4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3804,9 +3804,17 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, /* * Restore the original nodemask if it was potentially replaced with * &cpuset_current_mems_allowed to optimize the fast-path attempt. + * Also recalculate the starting point for the zonelist iterator or + * we could end up iterating over non-eligible zones endlessly. */ - if (cpusets_enabled()) + if (unlikely(ac.nodemask != nodemask)) { ac.nodemask = nodemask; + ac.preferred_zoneref = first_zones_zonelist(ac.zonelist, + ac.high_zoneidx, ac.nodemask); + if (!ac.preferred_zoneref->zone) + goto no_zone; + } + page = __alloc_pages_slowpath(alloc_mask, order, &ac); no_zone: -- 2.11.0