linux-kernel - [PATCH] vmpressure: Fix subtree pressure detection

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Date:	Wed, 27 Jan 2016 19:28:57 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] vmpressure: Fix subtree pressure detection

When vmpressure is called for the entire subtree under pressure we
mistakenly use vmpressure->scanned instead of vmpressure->tree_scanned
when checking if vmpressure work is to be scheduled. This results in
suppressing all vmpressure events in the legacy cgroup hierarchy. Fix
it.

Fixes: 8e8ae645249b ("mm: memcontrol: hook up vmpressure to socket pressure")
Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>
---
 mm/vmpressure.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 9a6c0704211c..149fdf6c5c56 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -248,9 +248,8 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
 
 	if (tree) {
 		spin_lock(&vmpr->sr_lock);
-		vmpr->tree_scanned += scanned;
+		scanned = vmpr->tree_scanned += scanned;
 		vmpr->tree_reclaimed += reclaimed;
-		scanned = vmpr->scanned;
 		spin_unlock(&vmpr->sr_lock);
 
 		if (scanned < vmpressure_win)
-- 
2.1.4