From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Rientjes <rientjes@google.com>,
        Michal Hocko <mhocko@suse.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ben Hutchings <ben.hutchings@codethink.co.uk>
Subject: [PATCH 4.4 021/101] mm, swap_cgroup: reschedule when neeed in swap_cgroup_swapoff()
Date: Mon,  3 Jul 2017 15:34:21 +0200
Message-Id: <20170703133338.054337126@linuxfoundation.org>
In-Reply-To: <20170703133334.237346187@linuxfoundation.org>
References: <20170703133334.237346187@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Rientjes <rientjes@google.com>

commit 460bcec84e11c75122ace5976214abbc596eb91b upstream.

We got need_resched() warnings in swap_cgroup_swapoff() because
swap_cgroup_ctrl[type].length is particularly large.

Reschedule when needed.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1704061315270.80559@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/swap_cgroup.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -205,6 +205,8 @@ void swap_cgroup_swapoff(int type)
 			struct page *page = map[i];
 			if (page)
 				__free_page(page);
+			if (!(i % SWAP_CLUSTER_MAX))
+				cond_resched();
 		}
 		vfree(map);
 	}