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 X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CA62C433E6 for ; Wed, 24 Feb 2021 20:06:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEDA064F14 for ; Wed, 24 Feb 2021 20:06:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233743AbhBXUGQ (ORCPT ); Wed, 24 Feb 2021 15:06:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:56702 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235165AbhBXUFg (ORCPT ); Wed, 24 Feb 2021 15:05:36 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0A5B364F08; Wed, 24 Feb 2021 20:04:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614197056; bh=qpY4DySb6Qdg0r072i2zKud5TA2ga17Nkt0ocrLYpx4=; h=Date:From:To:Subject:In-Reply-To:From; b=PosR8Gnp70bvAUnt3yMyiJSKJ7/KDjCL+wpzAfG7mzl13WMpvDlK2XKh5k5Oa55Fj y7f+hCESUIeE+Rr1P9rClfevjxPgXMlw4ONI08oqV/1Jix3ZQ889mynw2d7MsStHiP hznNLx0MPNvRRtp8+M7mhOSdznGfP5sEqL8SPi4A= Date: Wed, 24 Feb 2021 12:04:15 -0800 From: Andrew Morton To: akpm@linux-foundation.org, guro@fb.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, songmuchun@bytedance.com, torvalds@linux-foundation.org Subject: [patch 072/173] fs: buffer: use raw page_memcg() on locked page Message-ID: <20210224200415.uBhXwogkS%akpm@linux-foundation.org> In-Reply-To: <20210224115824.1e289a6895087f10c41dd8d6@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Johannes Weiner Subject: fs: buffer: use raw page_memcg() on locked page alloc_page_buffers() currently uses get_mem_cgroup_from_page() for charging the buffers to the page owner, which does an rcu-protected page->memcg lookup and acquires a reference. But buffer allocation has the page lock held throughout, which pins the page to the memcg and thereby the memcg - neither rcu nor holding an extra reference during the allocation are necessary. Use a raw page_memcg() instead. This was the last user of get_mem_cgroup_from_page(), delete it. Link: https://lkml.kernel.org/r/20210209190126.97842-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reported-by: Muchun Song Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Michal Hocko Signed-off-by: Andrew Morton --- fs/buffer.c | 4 ++-- include/linux/memcontrol.h | 7 ------- mm/memcontrol.c | 23 ----------------------- 3 files changed, 2 insertions(+), 32 deletions(-) --- a/fs/buffer.c~fs-buffer-use-raw-page_memcg-on-locked-page +++ a/fs/buffer.c @@ -847,7 +847,8 @@ struct buffer_head *alloc_page_buffers(s if (retry) gfp |= __GFP_NOFAIL; - memcg = get_mem_cgroup_from_page(page); + /* The page lock pins the memcg */ + memcg = page_memcg(page); old_memcg = set_active_memcg(memcg); head = NULL; @@ -868,7 +869,6 @@ struct buffer_head *alloc_page_buffers(s } out: set_active_memcg(old_memcg); - mem_cgroup_put(memcg); return head; /* * In case anything failed, we just free everything we got. --- a/include/linux/memcontrol.h~fs-buffer-use-raw-page_memcg-on-locked-page +++ a/include/linux/memcontrol.h @@ -680,8 +680,6 @@ struct mem_cgroup *mem_cgroup_from_task( struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm); -struct mem_cgroup *get_mem_cgroup_from_page(struct page *page); - struct lruvec *lock_page_lruvec(struct page *page); struct lruvec *lock_page_lruvec_irq(struct page *page); struct lruvec *lock_page_lruvec_irqsave(struct page *page, @@ -1190,11 +1188,6 @@ static inline struct mem_cgroup *get_mem { return NULL; } - -static inline struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) -{ - return NULL; -} static inline void mem_cgroup_put(struct mem_cgroup *memcg) { --- a/mm/memcontrol.c~fs-buffer-use-raw-page_memcg-on-locked-page +++ a/mm/memcontrol.c @@ -1047,29 +1047,6 @@ struct mem_cgroup *get_mem_cgroup_from_m } EXPORT_SYMBOL(get_mem_cgroup_from_mm); -/** - * get_mem_cgroup_from_page: Obtain a reference on given page's memcg. - * @page: page from which memcg should be extracted. - * - * Obtain a reference on page->memcg and returns it if successful. Otherwise - * root_mem_cgroup is returned. - */ -struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) -{ - struct mem_cgroup *memcg = page_memcg(page); - - if (mem_cgroup_disabled()) - return NULL; - - rcu_read_lock(); - /* Page should not get uncharged and freed memcg under us. */ - if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg = root_mem_cgroup; - rcu_read_unlock(); - return memcg; -} -EXPORT_SYMBOL(get_mem_cgroup_from_page); - static __always_inline struct mem_cgroup *active_memcg(void) { if (in_interrupt()) _