From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E336C6FD1C for ; Tue, 14 Mar 2023 10:02:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EEEC76B0072; Tue, 14 Mar 2023 06:02:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E77A98E0001; Tue, 14 Mar 2023 06:02:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CF26B6B0075; Tue, 14 Mar 2023 06:02:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id B80606B0072 for ; Tue, 14 Mar 2023 06:02:05 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 8848B160F2B for ; Tue, 14 Mar 2023 10:02:05 +0000 (UTC) X-FDA: 80567063010.08.12B2B53 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf07.hostedemail.com (Postfix) with ESMTP id 8D03E4002B for ; Tue, 14 Mar 2023 10:02:02 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=B3TInlRa; spf=pass (imf07.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678788122; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=F3V9UlH+4QbXycfDs9XgBP/KFr5npe8+4wtZALH2Ryk=; b=3siq7fGnzKJmeCJofgKi8MDoVeMOLVh/LZYSCscPgGp8tlWDT/fH1nS1oQq8/GfME/qTk8 1kRo3IolYqvhS/QfK5nIgzCK5HwSleoyLkvTeWRhk4rc752vIcQ1oJKBDRBUOdpBNx+OVi W6FH+SHd9X7NlGglDnsTUVDqB6Mpjmw= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=B3TInlRa; spf=pass (imf07.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678788122; a=rsa-sha256; cv=none; b=FXERC2Qif+0rKwTBBNGcgps4KVZuFa3S41fS8O0XGmxZsnF+SB5kxIW8C6QFPlViHvrTuc OLy08N4kvLVs9qOtOJDmuwUE7BAh751LVK5/C5XNeJbnuPls0bpfnKaYduRhV5QomGAGI5 TXYPfYMyqEEp/r/xnE7uaWczmUFB0J0= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 4812B1F88C; Tue, 14 Mar 2023 10:02:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1678788121; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=F3V9UlH+4QbXycfDs9XgBP/KFr5npe8+4wtZALH2Ryk=; b=B3TInlRa76gpBNGGVaMXKohYJ3fSl3MCkousy1D+tQbxukirNV4Sn+na4/YlHcdfuET39l +J2Kxha6ZHC3/F3y9wVKku3J7WyiMVU7becgzjmeWbg0VbPS5slkDvMbNuoQxvwaOBSHQE FKX3z3cGHStkhPxrMFv3tLHl+8KmSvw= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 283D713A26; Tue, 14 Mar 2023 10:02:01 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id eYKlCBlGEGQNfgAAMHmgww (envelope-from ); Tue, 14 Mar 2023 10:02:01 +0000 Date: Tue, 14 Mar 2023 11:02:00 +0100 From: Michal Hocko To: Yosry Ahmed Cc: Andrew Morton , Hugh Dickins , Johannes Weiner , 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: References: <20230313083452.1319968-1-yosryahmed@google.com> <20230313124431.fe901d79bc8c7dc96582539c@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: zpkgty5wwmggfcqofygatkq1zhuj8s46 X-Rspamd-Queue-Id: 8D03E4002B X-HE-Tag: 1678788122-232466 X-HE-Meta: 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 Aytn150w GU3gWv0HCdyXhyTNjGSiBagY4Q8Hn86Eg+djXZ5GRt3ys8bx7CCJcZRWbP7ihVCRZ6sUoExQimAnNbxaDF6IYpEHTnTLL3YFFtpVK63m7eRbYvSRyg97bKSgvsPxFcJIvF4rwtOHjtmYIVkUzioH3BE9zOUD9rBiODJ39eo6WGMeZXwBnyE5usxttWlfBB9cuPLmE/FbRrm3o5sJxXVV1Wn01OZQ3zA4zdzGB/NWgTRHMy09QRgE3nCAuMKJC8zZNmXwcMeRGtLjDKhX+DbCm0xehPPGDNPuKv2sL41F7B6ACoZAH4odtOfGLvsdmx9vLcru6OijFoD08E4wQn3cqu/te+mGixzYXbGohu8dwcEx0twk= 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 13-03-23 14:08:53, Yosry Ahmed wrote: > On Mon, Mar 13, 2023 at 12:44 PM Andrew Morton > wrote: > > > > 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? > > I guess it's a safety check so that we don't end up trying to cast a > tail page to a folio. My opinion is to go one step further and change > page_memcg_check() to do return the memcg of the head page, i.e: > > static inline struct mem_cgroup *page_memcg_check(struct page *page) > { > return folio_memcg_check(page_folio(page)); > } I would just stick with the existing code and put a comment that this function shouldn't be used in any new code and the folio counterpart should be used instead. -- Michal Hocko SUSE Labs