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Fri, 01 Oct 2021 19:03:06 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyei3tVv14fNrp7a4mEN1eQaA52YTKDfW7PRXgu/igrMlJ2dGo/5jNaxmZZ+RUooFfL7OOUfw== X-Received: by 2002:ac8:51d7:: with SMTP id d23mr1366434qtn.332.1633140186308; Fri, 01 Oct 2021 19:03:06 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id c6sm4839644qtx.72.2021.10.01.19.03.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 Oct 2021 19:03:06 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH 2/3] mm, memcg: Remove obsolete memcg_free_kmem() To: Roman Gushchin Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Vlastimil Babka , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Muchun Song References: <20211001190938.14050-1-longman@redhat.com> <20211001190938.14050-3-longman@redhat.com> Message-ID: Date: Fri, 1 Oct 2021 22:03:05 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 36BAEF00034D X-Stat-Signature: 4y36rpbqq7tgi4e5hrwp3w6h3qp74cfb Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ey6Tdmru; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf16.hostedemail.com: domain of llong@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=llong@redhat.com X-HE-Tag: 1633140191-189239 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 10/1/21 8:01 PM, Roman Gushchin wrote: > On Fri, Oct 01, 2021 at 03:09:37PM -0400, Waiman Long wrote: >> Since commit d648bcc7fe65 ("mm: kmem: make memcg_kmem_enabled() >> irreversible"), the only thing memcg_free_kmem() does is to call >> memcg_offline_kmem() when the memcg is still online. However, >> memcg_offline_kmem() is only called from mem_cgroup_css_free() which >> cannot be reached if the memcg hasn't been offlined first. > Hm, is it true? What if online_css() fails? I just realize that memcg_online_kmem() is called at css_create(). So yes, if css_online() fails (i.e. ENOMEM), we will need to do memcg_offline_kmem(). >> As this >> function now serves no purpose, we should just remove it. > It looks like we can just use memcg_offline_kmem() instead of > memcg_free_kmem(). Right, memcg_free_kmem() isn't the right name for that. I agree that we should just change mem_cgroup_css_free() to call memcg_offline_kmem() directly. Will update the patch accordingly. Thanks, Longman