linux-kernel - [PATCH 2/5] mm: migration of hugetlbfs page skip memcg

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Date:   Sun, 30 Aug 2020 14:01:30 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Alex Shi <alex.shi@...ux.alibaba.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>, Qian Cai <cai@....pw>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 2/5] mm: migration of hugetlbfs page skip memcg

hugetlbfs pages do not participate in memcg: so although they do find
most of migrate_page_states() useful, it would be better if they did
not call into mem_cgroup_migrate() - where Qian Cai reported that LTP's
move_pages12 triggers the warning in Alex Shi's prospective commit
"mm/memcg: warning on !memcg after readahead page charged".

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
This fixes a likely future warning, but is just a cleanup right now.

 mm/migrate.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 5.9-rc2/mm/migrate.c	2020-08-16 17:32:50.665507048 -0700
+++ linux/mm/migrate.c	2020-08-28 17:42:07.967278385 -0700
@@ -668,7 +668,8 @@ void migrate_page_states(struct page *ne
 
 	copy_page_owner(page, newpage);
 
-	mem_cgroup_migrate(page, newpage);
+	if (!PageHuge(page))
+		mem_cgroup_migrate(page, newpage);
 }
 EXPORT_SYMBOL(migrate_page_states);