linux-kernel - Re: [patch v2] mm, memcg: do not retry precharge charges

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Date:   Fri, 13 Jan 2017 02:09:53 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch v2] mm, memcg: do not retry precharge charges

When memory.move_charge_at_immigrate is enabled and precharges are
depleted during move, mem_cgroup_move_charge_pte_range() will attempt to
increase the size of the precharge.

Prevent precharges from ever looping by setting __GFP_NORETRY.  This was
probably the intention of the GFP_KERNEL & ~__GFP_NORETRY, which is
pointless as written.

Fixes: 0029e19ebf84 ("mm: memcontrol: remove explicit OOM parameter in charge path")
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/memcontrol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4353,9 +4353,9 @@ static int mem_cgroup_do_precharge(unsigned long count)
 		return ret;
 	}
 
-	/* Try charges one by one with reclaim */
+	/* Try charges one by one with reclaim, but do not retry */
 	while (count--) {
-		ret = try_charge(mc.to, GFP_KERNEL & ~__GFP_NORETRY, 1);
+		ret = try_charge(mc.to, GFP_KERNEL | __GFP_NORETRY, 1);
 		if (ret)
 			return ret;
 		mc.precharge++;