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Subject: Re: [Resend PATCH 2/6] mm/memcg: remove useless check on
 page->mem_cgroup
To:     Michal Hocko <mhocko@suse.com>
Cc:     akpm@linux-foundation.org, Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <1597144232-11370-1-git-send-email-alex.shi@linux.alibaba.com>
 <1597144232-11370-2-git-send-email-alex.shi@linux.alibaba.com>
 <20200811113008.GK4793@dhcp22.suse.cz>
From:   Alex Shi <alex.shi@linux.alibaba.com>
Message-ID: <776b0e6f-4129-9fb9-0f66-47757cf320d5@linux.alibaba.com>
Date:   Tue, 11 Aug 2020 20:54:18 +0800
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From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed, 5 Aug 2020 21:02:30 +0800
Subject: [PATCH 2/6] memcg: bail out early from swap accounting when memcg is
 disabled

If we disabled memcg by cgroup_disable=memory, the swap charges are
still called. Let's return from the funcs earlier.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
@@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
+	if (mem_cgroup_disabled())
+		return 0;
+
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
 
-- 
1.8.3.1