linux-kernel - Re: [PATCH] mm/workingset: do not forget to unlock page

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Message-ID: <20160203104136.GA517@swordfish>
Date:	Wed, 3 Feb 2016 19:41:36 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Vladimir Davydov <vdavydov@...tuozzo.com>,
	Michal Hocko <mhocko@...e.cz>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH] mm/workingset: do not forget to unlock page

On (02/03/16 18:58), Sergey Senozhatsky wrote:
> 
> Do not leave page locked (and RCU read side locked) when
> return from workingset_activation() due to disabled memcg
> or page not being a page_memcg().

d'oh... sorry, the commit message is simply insane.


apparently the patch fixes a new code
	mm-workingset-per-cgroup-cache-thrash-detection.patch added to -mm tree
	mm-simplify-lock_page_memcg.patch added to -mm tree


so if there is an option to fold this patch into mm-simplify-lock_page_memcg,
for example, as a -fix, then I wouldn't mind at all.



a better commit message
===8<====8<====

>From 1d6315221f2f81c53c99f9980158f8ae49dbd582 Mon Sep 17 00:00:00 2001
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Date: Wed, 3 Feb 2016 18:49:16 +0900
Subject: [PATCH] mm/workingset: do not forget to unlock_page in workingset_activation

Do not return from workingset_activation() with locked rcu and page.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 mm/workingset.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 14522ed..54138a9 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -315,8 +315,10 @@ void workingset_activation(struct page *page)
 	 * XXX: See workingset_refault() - this should return
 	 * root_mem_cgroup even for !CONFIG_MEMCG.
 	 */
-	if (!mem_cgroup_disabled() && !page_memcg(page))
+	if (!mem_cgroup_disabled() && !page_memcg(page)) {
+		unlock_page_memcg(page);
 		return;
+	}
 	lruvec = mem_cgroup_zone_lruvec(page_zone(page), page_memcg(page));
 	atomic_long_inc(&lruvec->inactive_age);
 	unlock_page_memcg(page);
-- 
2.7.0