Re: [PATCH] mm/memcg: remove useless check on page->mem_cgroup

Alex Shi
2020-08-05T19:58:40Z

在 2020/8/5 下午8:28, Alex Shi 写道:
> The last patch has a problem on define. this version could fix it.
>
> BTW, I see some !memcg happens when MEMCG compilered but disabled by cgroup_disable
>
>
> [ 94.657666] ---[ end trace f1f34bfc3b32ed2f ]---
> [ 95.138995] anon flags: 0x5005b48008000d(locked|uptodate|dirty|swapbacked)
> [ 95.146220] raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
> [ 95.154549] raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
> [ 95.162876] page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
>
>

The following patch may helpful.

From 8bfb26a2e37e08dc61d20212bcfa5812a367ba94 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed, 5 Aug 2020 20:32:12 +0800
Subject: [PATCH] mm/memcg: don't try charge swap if memcg disabled

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

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.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 cb07a48d53aa..65f2b42d25af 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7163,6 +7163,9 @@ 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;

@@ -7228,6 +7231,9 @@ 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