linux-kernel - [PATCH 4.4 24/30] swap: cond_resched in swap_cgroup

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Message-Id: <20170619152034.567871881@linuxfoundation.org>
Date:   Mon, 19 Jun 2017 23:20:58 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yu Zhao <yuzhao@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.4 24/30] swap: cond_resched in swap_cgroup_prepare()

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Yu Zhao <yuzhao@...gle.com>

commit ef70762948dde012146926720b70e79736336764 upstream.

I saw need_resched() warnings when swapping on large swapfile (TBs)
because continuously allocating many pages in swap_cgroup_prepare() took
too long.

We already cond_resched when freeing page in swap_cgroup_swapoff().  Do
the same for the page allocation.

Link: http://lkml.kernel.org/r/20170604200109.17606-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@...gle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Acked-by: Vladimir Davydov <vdavydov.dev@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/swap_cgroup.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -48,6 +48,9 @@ static int swap_cgroup_prepare(int type)
 		if (!page)
 			goto not_enough_page;
 		ctrl->map[idx] = page;
+
+		if (!(idx % SWAP_CLUSTER_MAX))
+			cond_resched();
 	}
 	return 0;
 not_enough_page: