From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756528AbcEaVo3 (ORCPT ); Tue, 31 May 2016 17:44:29 -0400 Received: from mx2.suse.de ([195.135.220.15]:60699 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754643AbcEaVo1 (ORCPT ); Tue, 31 May 2016 17:44:27 -0400 Subject: Re: BUG: scheduling while atomic: cron/668/0x10c9a0c0 (was: Re: mm, page_alloc: avoid looking up the first zone in a zonelist twice) To: Mel Gorman , Geert Uytterhoeven References: <20160530155644.GP2527@techsingularity.net> Cc: Andrew Morton , Linux Kernel Mailing List , Linux MM , linux-m68k From: Vlastimil Babka Message-ID: <574E05B8.3060009@suse.cz> Date: Tue, 31 May 2016 23:44:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <20160530155644.GP2527@techsingularity.net> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/30/2016 05:56 PM, Mel Gorman wrote: > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index dba8cfd0b2d6..f2c1e47adc11 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3232,6 +3232,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > * allocations are system rather than user orientated > */ > ac->zonelist = node_zonelist(numa_node_id(), gfp_mask); > + ac->preferred_zoneref = first_zones_zonelist(ac->zonelist, > + ac->high_zoneidx, ac->nodemask); > + ac->classzone_idx = zonelist_zone_idx(ac->preferred_zoneref); > page = get_page_from_freelist(gfp_mask, order, > ALLOC_NO_WATERMARKS, ac); > if (page) > Even if that didn't help for this report, I think it's needed too (except the classzone_idx which doesn't exist anymore?). And I think the following as well. (the changed comment could be also just deleted). diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f8f3bfc435ee..0a8d8e2bf331 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3808,7 +3808,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, /* Dirty zone balancing only done in the fast path */ ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE); - /* The preferred zone is used for statistics later */ + /* The preferred zone is crucial for get_page_from_freelist */ ac.preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx, ac.nodemask); if (!ac.preferred_zoneref) { @@ -3832,8 +3832,11 @@ __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. */ - if (cpusets_enabled()) + if (cpusets_enabled()) { ac.nodemask = nodemask; + ac.preferred_zoneref = first_zones_zonelist(ac.zonelist, + ac.high_zoneidx, ac.nodemask); + } page = __alloc_pages_slowpath(alloc_mask, order, &ac);