linux-kernel - [patch] mm, oom: header nodemask is NULL when cpusets are disabled

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Date:   Thu, 19 Jan 2017 14:57:36 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>
cc:     Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: [patch] mm, oom: header nodemask is NULL when cpusets are disabled

Commit 82e7d3abec86 ("oom: print nodemask in the oom report") implicitly 
sets the allocation nodemask to cpuset_current_mems_allowed when there is 
no effective mempolicy.  cpuset_current_mems_allowed is only effective 
when cpusets are enabled, which is also printed by dump_header(), so 
setting the nodemask to cpuset_current_mems_allowed is redundant and 
prevents debugging issues where ac->nodemask is not set properly in the 
page allocator.

This provides better debugging output since 
cpuset_print_current_mems_allowed() is already provided.

Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/oom_kill.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -403,12 +403,14 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
 
 static void dump_header(struct oom_control *oc, struct task_struct *p)
 {
-	nodemask_t *nm = (oc->nodemask) ? oc->nodemask : &cpuset_current_mems_allowed;
-
-	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
-		current->comm, oc->gfp_mask, &oc->gfp_mask,
-		nodemask_pr_args(nm), oc->order,
-		current->signal->oom_score_adj);
+	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=",
+		current->comm, oc->gfp_mask, &oc->gfp_mask);
+	if (oc->nodemask)
+		pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
+	else
+		pr_cont("(null)\n");
+	pr_cont(",  order=%d, oom_score_adj=%hd\n",
+		oc->order, current->signal->oom_score_adj);
 	if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
 		pr_warn("COMPACTION is disabled!!!\n");
 
@@ -417,7 +419,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
 	if (oc->memcg)
 		mem_cgroup_print_oom_info(oc->memcg, p);
 	else
-		show_mem(SHOW_MEM_FILTER_NODES, nm);
+		show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
 	if (sysctl_oom_dump_tasks)
 		dump_tasks(oc->memcg, oc->nodemask);
 }