linux-kernel - [PATCH v18 12/32] mm/memcg: optimize mem_cgroup_page

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Date:   Mon, 24 Aug 2020 20:54:45 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        tj@...nel.org, hughd@...gle.com, khlebnikov@...dex-team.ru,
        daniel.m.jordan@...cle.com, willy@...radead.org,
        hannes@...xchg.org, lkp@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        shakeelb@...gle.com, iamjoonsoo.kim@....com,
        richard.weiyang@...il.com, kirill@...temov.name,
        alexander.duyck@...il.com, rong.a.chen@...el.com, mhocko@...e.com,
        vdavydov.dev@...il.com, shy828301@...il.com
Cc:     Michal Hocko <mhocko@...nel.org>
Subject: [PATCH v18 12/32] mm/memcg: optimize mem_cgroup_page_lruvec

From: Hugh Dickins <hughd@...gle.com>

Add READ_ONCE on page->mem_cgroup, since we will check it later.
Also the page should not be PageTail(page), so add a check.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Vladimir Davydov <vdavydov.dev@...il.com>
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: cgroups@...r.kernel.org
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 505f54087e82..65c1e873153e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1321,7 +1321,8 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd
 		goto out;
 	}
 
-	memcg = page->mem_cgroup;
+	VM_BUG_ON_PAGE(PageTail(page), page);
+	memcg = READ_ONCE(page->mem_cgroup);
 	/* Readahead page is charged too, to see if other page uncharged */
 	VM_WARN_ON_ONCE_PAGE(!memcg, page);
 	if (!memcg)
-- 
1.8.3.1