From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 821B46B0092 for ; Wed, 27 May 2015 13:10:21 -0400 (EDT) Received: by pdbqa5 with SMTP id qa5so21514293pdb.0 for ; Wed, 27 May 2015 10:10:21 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id lw5si26815670pab.204.2015.05.27.10.10.19 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 May 2015 10:10:19 -0700 (PDT) Date: Wed, 27 May 2015 13:09:55 -0400 From: Johannes Weiner Subject: Re: [PATCH v2 11/51] memcg: implement mem_cgroup_css_from_page() Message-ID: <20150527170955.GA25324@cmpxchg.org> References: <1432329245-5844-1-git-send-email-tj@kernel.org> <1432329245-5844-12-git-send-email-tj@kernel.org> <20150527161344.GO7099@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150527161344.GO7099@htj.duckdns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, khlebnikov@yandex-team.ru On Wed, May 27, 2015 at 12:13:44PM -0400, Tejun Heo wrote: > From 26bab580abfc441c841c1983469b8b86f5a8ef5c Mon Sep 17 00:00:00 2001 > From: Tejun Heo > Date: Wed, 27 May 2015 12:08:29 -0400 > > Implement mem_cgroup_css_from_page() which returns the > cgroup_subsys_state of the memcg associated with a given page. This > will be used by cgroup writeback support. > > This function assumes that page->mem_cgroup association doesn't change > until the page is released, which is true on the default hierarchy as > long as mem_cgroup_migrate() is not used. As the only user of > mem_cgroup_migrate() is FUSE which won't support cgroup writeback for > the time being, this works for now, and mem_cgroup_migrate() will soon > be updated so that the invariant actually holds. Regular page migration uses mem_cgroup_migrate() as well, but it's not a problem as it ensures that the old page doesn't have any outstanding references at that point. It's only replace_page_cache_page() that calls mem_cgroup_migrate() on a live page breaking mem_cgroup_css_from_page(). So the page looks fine, I'd just update the culprit function in the changelog and kerneldoc. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org