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bh=W94HEWIftode6/6zR57Ubi2uQZUtKVwUT0RuE4adZeU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YFSLYeGI819Stzjl6ClJqdTFh/Ihg6fYTsWQvoQiC78GMGNGqG5a6KLj5e9mRpPfh dnPIAQIl+j99tqT3dq7ZMEWKrX4l/K2ECdNDdtXqK1+TbyzDgcljQWvIBlqMnetHE5 OJlMJZ1aZJc+hhnYtMdNrG7sdM6aBZXF+dGGE81Q= Date: Mon, 13 Mar 2023 12:44:31 -0700 From: Andrew Morton To: Yosry Ahmed Cc: Hugh Dickins , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Naoya Horiguchi , Miaohe Lin , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org Subject: Re: [PATCH] memcg: page_cgroup_ino() get memcg from compound_head(page) Message-Id: <20230313124431.fe901d79bc8c7dc96582539c@linux-foundation.org> In-Reply-To: <20230313083452.1319968-1-yosryahmed@google.com> References: <20230313083452.1319968-1-yosryahmed@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3F1CF16000F X-Rspam-User: X-Stat-Signature: 3bukg8eurq7gon4fnxb9rfcm1cny5y99 X-HE-Tag: 1678736675-824988 X-HE-Meta: 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 wg5HmS8c 2uZsz2IN5hbwMUkImMfVozpyy39S4enWff6oTDRy1614yFCtQLUpA/uWeZcAr+1spdVnEWJdQNJrPaOmUvjB8Vlc7BRZdJghFZoOZLReKnzQSPGmg+Jy9fQGDYQqg3QJHb5ZqFVf1ee2g8n3lpxe0A0vRMAggPw4dRLXFhvwswFHFJ70pra5XPLmkmjO4awffsqOJFtEO86Idv13ftaANjEgGMaGDTLQwKPFCRN/QoiLhGz3K5pGFXEDvybJiqsGyGqenQEZjDn/WB+1goQuqpGfs5rHG21Nn0u+P0IWhKGniuYIdbj/LPqHRK5YdffESoFM33CiL669OHVov5Mni4I4XtCrv49HX01xUEnQOzz1BIwQvVS08Tj2pj68SJjRrbhIwLyt8i8qjZ7X0szykhXdhcnKUdycjZpeu+Y5ZtdAQC4ZkI2ewvplnACJBLPraeXqRrkazxhze/PdntgiZDyFYUsgWmBHGJ+oupQwxkxTenUo= 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 Mon, 13 Mar 2023 08:34:52 +0000 Yosry Ahmed wrote: > From: Hugh Dickins > > In a kernel with added WARN_ON_ONCE(PageTail) in page_memcg_check(), we > observed a warning from page_cgroup_ino() when reading > /proc/kpagecgroup. If this is the only known situation in which page_memcg_check() is passed a tail page, why does page_memcg_check() have if (PageTail(page)) return NULL; ? Can we remove this to simplify, streamline and clarify?