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Wed, 13 May 2020 05:22:25 -0700 (PDT) MIME-Version: 1.0 References: <20200513090502.GV29153@dhcp22.suse.cz> <76f71776-d049-7407-8574-86b6e9d80704@huawei.com> <20200513112905.GX29153@dhcp22.suse.cz> <3a721f62-5a66-8bc5-247b-5c8b7c51c555@huawei.com> In-Reply-To: <3a721f62-5a66-8bc5-247b-5c8b7c51c555@huawei.com> From: Shakeel Butt Date: Wed, 13 May 2020 05:22:13 -0700 Message-ID: Subject: Re: [PATCH v2] memcg: Fix memcg_kmem_bypass() for remote memcg charging To: Zefan Li Cc: Michal Hocko , Johannes Weiner , Vladimir Davydov , Cgroups , Linux MM , Andrew Morton , Roman Gushchin Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 13, 2020 at 4:47 AM Zefan Li wrote: > > While trying to use remote memcg charging in an out-of-tree kernel module > I found it's not working, because the current thread is a workqueue thread. > > As we will probably encounter this issue in the future as the users of > memalloc_use_memcg() grow, it's better we fix it now. > > Signed-off-by: Zefan Li > --- > > v2: add a comment as sugguested by Michal. and add changelog to explain why > upstream kernel needs this fix. > > --- > > mm/memcontrol.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index a3b97f1..43a12ed 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2802,6 +2802,9 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg, > > static inline bool memcg_kmem_bypass(void) > { > + /* Allow remote memcg charging in kthread contexts. */ > + if (unlikely(current->active_memcg)) > + return false; What about __GFP_ACCOUNT allocations in the interrupt context? e.g. memalloc_use_memcg(memcg); --->interrupt --->alloc_page(GFP_KERNEL_ACCOUNT) in interrupt context. alloc_page(GFP_KERNEL_ACCOUNT); memalloc_unuse_memcg(); > if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD)) > return true; > return false; > -- > 2.7.4 >