From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752968AbbE0QNw (ORCPT ); Wed, 27 May 2015 12:13:52 -0400 Received: from mail-qc0-f170.google.com ([209.85.216.170]:36717 "EHLO mail-qc0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751358AbbE0QNt (ORCPT ); Wed, 27 May 2015 12:13:49 -0400 Date: Wed, 27 May 2015 12:13:44 -0400 From: Tejun Heo To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.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 Subject: [PATCH v2 11/51] memcg: implement mem_cgroup_css_from_page() Message-ID: <20150527161344.GO7099@htj.duckdns.org> References: <1432329245-5844-1-git-send-email-tj@kernel.org> <1432329245-5844-12-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1432329245-5844-12-git-send-email-tj@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>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. v2: Trigger WARN if the function is used on the traditional hierarchies and add comment about the assumed invariant. Signed-off-by: Tejun Heo Cc: Johannes Weiner Cc: Michal Hocko --- Added WARN and comments. No functional change. git branches updated accordingly. Thanks. include/linux/memcontrol.h | 1 + mm/memcontrol.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 294498f..637ef62 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -115,6 +115,7 @@ static inline bool mm_match_cgroup(struct mm_struct *mm, } extern struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg); +extern struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page); struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *, struct mem_cgroup *, diff --git a/mm/memcontrol.c b/mm/memcontrol.c index b22a92b..c76b85c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -598,6 +598,37 @@ struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg) return &memcg->css; } +/** + * mem_cgroup_css_from_page - css of the memcg associated with a page + * @page: page of interest + * + * This function is guaranteed to return a valid cgroup_subsys_state and + * the returned css remains associated with @page until it is released. + * + * This can only be used on the default hierarchy as @page's memcg + * association may change on the traditional hierarchies. Use + * try_get_mem_cgroup_from_page() instead on the traditional hierarchies. + * + * XXX: The above comment isn't true yet as mem_cgroup_migrate() can modify + * the association before @page is released even on the default + * hierarchy; however, the current and planned usages don't mix the + * the two functions and mem_cgroup_migrate() will soon be updated to + * make the invariant actually true. + */ +struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page) +{ + struct cgroup_subsys_state *css; + + if (page->mem_cgroup) + css = &page->mem_cgroup->css; + else + css = &root_mem_cgroup->css; + + WARN_ON_ONCE(!cgroup_on_dfl(css->cgroup)); + + return css; +} + static struct mem_cgroup_per_zone * mem_cgroup_page_zoneinfo(struct mem_cgroup *memcg, struct page *page) { -- 2.4.0