From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752128AbdEJI1t (ORCPT ); Wed, 10 May 2017 04:27:49 -0400 Received: from mail-pg0-f68.google.com ([74.125.83.68]:33276 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751901AbdEJI1r (ORCPT ); Wed, 10 May 2017 04:27:47 -0400 From: Nick Desaulniers Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, mhocko@suse.com, vbabka@suse.cz, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Nick Desaulniers Subject: [Patch v2] mm/vmscan: fix unsequenced modification and access warning Date: Wed, 10 May 2017 01:27:34 -0700 Message-Id: <20170510082734.2055-1-nick.desaulniers@gmail.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170510071511.GA31466@dhcp22.suse.cz> References: <20170510071511.GA31466@dhcp22.suse.cz> To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Clang flags this file with the -Wunsequenced error that GCC does not have. unsequenced modification and access to 'gfp_mask' It seems that gfp_mask is both read and written without a sequence point in between, which is undefined behavior. Signed-off-by: Nick Desaulniers --- Changes in v2: - don't assign back to gfp_mask, reuse sc.gfp_mask - initialize reclaim_idx directly, without classzone_idx mm/vmscan.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4e7ed65842af..d32c42d17935 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2958,7 +2958,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, unsigned long nr_reclaimed; struct scan_control sc = { .nr_to_reclaim = SWAP_CLUSTER_MAX, - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)), + .gfp_mask = current_gfp_context(gfp_mask), .reclaim_idx = gfp_zone(gfp_mask), .order = order, .nodemask = nodemask, @@ -2973,12 +2973,12 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, * 1 is returned so that the page allocator does not OOM kill at this * point. */ - if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask)) + if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask)) return 1; trace_mm_vmscan_direct_reclaim_begin(order, sc.may_writepage, - gfp_mask, + sc.gfp_mask, sc.reclaim_idx); nr_reclaimed = do_try_to_free_pages(zonelist, &sc); @@ -3763,16 +3763,15 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in const unsigned long nr_pages = 1 << order; struct task_struct *p = current; struct reclaim_state reclaim_state; - int classzone_idx = gfp_zone(gfp_mask); struct scan_control sc = { .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)), + .gfp_mask = current_gfp_context(gfp_mask), .order = order, .priority = NODE_RECLAIM_PRIORITY, .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE), .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP), .may_swap = 1, - .reclaim_idx = classzone_idx, + .reclaim_idx = gfp_zone(gfp_mask), }; cond_resched(); @@ -3782,7 +3781,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in * and RECLAIM_UNMAP. */ p->flags |= PF_MEMALLOC | PF_SWAPWRITE; - lockdep_set_current_reclaim_state(gfp_mask); + lockdep_set_current_reclaim_state(sc.gfp_mask); reclaim_state.reclaimed_slab = 0; p->reclaim_state = &reclaim_state; -- 2.11.0