From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752356AbbCMO5j (ORCPT ); Fri, 13 Mar 2015 10:57:39 -0400 Received: from mx2.parallels.com ([199.115.105.18]:33593 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751469AbbCMO5f (ORCPT ); Fri, 13 Mar 2015 10:57:35 -0400 From: Vladimir Davydov To: Andrew Morton CC: Johannes Weiner , Michal Hocko , Tejun Heo , Li Zefan , , , Subject: [PATCH -mm] memcg: zap mem_cgroup_lookup Date: Fri, 13 Mar 2015 17:57:22 +0300 Message-ID: <1426258642-14074-1-git-send-email-vdavydov@parallels.com> X-Mailer: git-send-email 1.7.10.4 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org mem_cgroup_lookup is a wrapper around mem_cgroup_from_id, which checks that id != 0 before issuing the function call. Today, there is no point in this additional check apart from optimization, because there is no css with id <= 0, so that css_from_id, called by mem_cgroup_from_id, will return NULL for any id <= 0. Since mem_cgroup_from_id is only called from mem_cgroup_lookup, let us zap mem_cgroup_lookup, substituting calls to it with mem_cgroup_from_id and moving the check if id > 0 to css_from_id. Signed-off-by: Vladimir Davydov --- kernel/cgroup.c | 2 +- mm/memcontrol.c | 24 ++++++++---------------- 2 files changed, 9 insertions(+), 17 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 29a7b2cc593e..747e953ffee9 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5451,7 +5451,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss) { WARN_ON_ONCE(!rcu_read_lock_held()); - return idr_find(&ss->css_idr, id); + return id > 0 ? idr_find(&ss->css_idr, id) : NULL; } #ifdef CONFIG_CGROUP_DEBUG diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d18d3a6e7337..f9df75ef55d7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -454,6 +454,12 @@ static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg) return memcg->css.id; } +/* + * A helper function to get mem_cgroup from ID. must be called under + * rcu_read_lock(). The caller is responsible for calling + * css_tryget_online() if the mem_cgroup is used for charging. (dropping + * refcnt from swap can be called against removed memcg.) + */ static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id) { struct cgroup_subsys_state *css; @@ -2341,20 +2347,6 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) } /* - * A helper function to get mem_cgroup from ID. must be called under - * rcu_read_lock(). The caller is responsible for calling - * css_tryget_online() if the mem_cgroup is used for charging. (dropping - * refcnt from swap can be called against removed memcg.) - */ -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id) -{ - /* ID 0 is unused ID */ - if (!id) - return NULL; - return mem_cgroup_from_id(id); -} - -/* * try_get_mem_cgroup_from_page - look up page's memcg association * @page: the page * @@ -2380,7 +2372,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page) ent.val = page_private(page); id = lookup_swap_cgroup_id(ent); rcu_read_lock(); - memcg = mem_cgroup_lookup(id); + memcg = mem_cgroup_from_id(id); if (memcg && !css_tryget_online(&memcg->css)) memcg = NULL; rcu_read_unlock(); @@ -5859,7 +5851,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry) id = swap_cgroup_record(entry, 0); rcu_read_lock(); - memcg = mem_cgroup_lookup(id); + memcg = mem_cgroup_from_id(id); if (memcg) { if (!mem_cgroup_is_root(memcg)) page_counter_uncharge(&memcg->memsw, 1); -- 1.7.10.4