在 2020/8/11 下午9:56, Michal Hocko 写道: > On Tue 11-08-20 20:54:18, Alex Shi wrote: >> >From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001 >> From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> >> 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. > They are not, are they? page->memcg will be NULL and so the charge is > skipped and that will trigger a warning with your current ordering. Hi Michal, Thanks for comment! Looks like we both agree the memcg wasn't charged, but funcs just are called. :) > > Let me repeat again. Either you put it first in the series and argue > that we can bail out early or keep the ordering then this makes sure the > warning doesn't trigger. > Is the following commit log fine? Thanks! Alex >From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001 From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Date: Wed, 5 Aug 2020 21:02:30 +0800 Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg is disabled If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL and so the charge is skipped and that will trigger a warning like below. Let's return from the funcs earlier. ---[ end trace f1f34bfc3b32ed2f ]--- anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked) raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1 raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000 page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg) Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Reviewed-by: Roman Gushchin <guro@xxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: cgroups@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx --- 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
