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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 1906EC433DF for ; Mon, 10 Aug 2020 09:55:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D5217206B5 for ; Mon, 10 Aug 2020 09:55:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D5217206B5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 543E06B0006; Mon, 10 Aug 2020 05:55:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F4D66B0007; Mon, 10 Aug 2020 05:55:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 40A126B0008; Mon, 10 Aug 2020 05:55:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0250.hostedemail.com [216.40.44.250]) by kanga.kvack.org (Postfix) with ESMTP id 2A4216B0006 for ; Mon, 10 Aug 2020 05:55:03 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C847A180AD801 for ; Mon, 10 Aug 2020 09:55:02 +0000 (UTC) X-FDA: 77134200444.14.angle22_210cf8d26fd9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id 83F3D18229837 for ; Mon, 10 Aug 2020 09:55:02 +0000 (UTC) X-HE-Tag: angle22_210cf8d26fd9 X-Filterd-Recvd-Size: 5487 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Mon, 10 Aug 2020 09:55:01 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B4197AC61; Mon, 10 Aug 2020 09:55:20 +0000 (UTC) Date: Mon, 10 Aug 2020 11:55:00 +0200 From: Michal Hocko To: Alex Shi Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memcg: remove useless check on page->mem_cgroup Message-ID: <20200810095500.GE4773@dhcp22.suse.cz> References: <1596166480-22814-1-git-send-email-alex.shi@linux.alibaba.com> <20200731151655.GB491801@cmpxchg.org> <9338716f-ca0e-057f-8d94-03e2b3f70281@linux.alibaba.com> <20200803081815.GD5174@dhcp22.suse.cz> <92dd8e68-8095-72c5-0144-2a084e4d5993@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <92dd8e68-8095-72c5-0144-2a084e4d5993@linux.alibaba.com> X-Rspamd-Queue-Id: 83F3D18229837 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 Wed 05-08-20 20:28:33, Alex Shi wrote: [...] > >From 2ca3e87fd3878ab729551682ad083a70f15bb3fc Mon Sep 17 00:00:00 2001 > From: Alex Shi > Date: Sat, 1 Aug 2020 10:43:55 +0800 > Subject: [PATCH v3] mm/memcg: warning on !memcg after readahead page charged > > Since readahead page is charged on memcg too, in theory we don't have to > check this exception now. Before safely remove them all, add a warning > for the unexpected !memcg. > > Signed-off-by: Alex Shi > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Vladimir Davydov > Cc: Andrew Morton > Cc: cgroups@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org Looks good to me. I am not familiar with the section tweaks but that should be ok. Acked-by: Michal Hocko Once you collect more feedback, please send both patches so that they do not get lost in this thread. Thanks! > --- > include/linux/mmdebug.h | 13 +++++++++++++ > mm/memcontrol.c | 15 ++++++++------- > 2 files changed, 21 insertions(+), 7 deletions(-) > > diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h > index 2ad72d2c8cc5..4ed52879ce55 100644 > --- a/include/linux/mmdebug.h > +++ b/include/linux/mmdebug.h > @@ -37,6 +37,18 @@ > BUG(); \ > } \ > } while (0) > +#define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \ > + static bool __section(.data.once) __warned; \ > + int __ret_warn_once = !!(cond); \ > + \ > + if (unlikely(__ret_warn_once && !__warned)) { \ > + dump_page(page, "VM_WARN_ON_ONCE_PAGE(" __stringify(cond)")");\ > + __warned = true; \ > + WARN_ON(1); \ > + } \ > + unlikely(__ret_warn_once); \ > +}) > + > #define VM_WARN_ON(cond) (void)WARN_ON(cond) > #define VM_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond) > #define VM_WARN_ONCE(cond, format...) (void)WARN_ONCE(cond, format) > @@ -48,6 +60,7 @@ > #define VM_BUG_ON_MM(cond, mm) VM_BUG_ON(cond) > #define VM_WARN_ON(cond) BUILD_BUG_ON_INVALID(cond) > #define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond) > +#define VM_WARN_ON_ONCE_PAGE(cond, page) BUILD_BUG_ON_INVALID(cond) > #define VM_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond) > #define VM_WARN(cond, format...) BUILD_BUG_ON_INVALID(cond) > #endif > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 130093bdf74b..299382fc55a9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1322,10 +1322,8 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd > } > > memcg = page->mem_cgroup; > - /* > - * Swapcache readahead pages are added to the LRU - and > - * possibly migrated - before they are charged. > - */ > + /* Readahead page is charged too, to see if other page uncharged */ > + VM_WARN_ON_ONCE_PAGE(!memcg, page); > if (!memcg) > memcg = root_mem_cgroup; > > @@ -6906,8 +6904,9 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > if (newpage->mem_cgroup) > return; > > - /* Swapcache readahead pages can get replaced before being charged */ > memcg = oldpage->mem_cgroup; > + /* Readahead page is charged too, to see if other page uncharged */ > + VM_WARN_ON_ONCE_PAGE(!memcg, oldpage); > if (!memcg) > return; > > @@ -7104,7 +7103,8 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) > > memcg = page->mem_cgroup; > > - /* Readahead page, never charged */ > + /* Readahead page is charged too, to see if other page uncharged */ > + VM_WARN_ON_ONCE_PAGE(!memcg, page); > if (!memcg) > return; > > @@ -7168,7 +7168,8 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry) > > memcg = page->mem_cgroup; > > - /* Readahead page, never charged */ > + /* Readahead page is charged too, to see if other page uncharged */ > + VM_WARN_ON_ONCE_PAGE(!memcg, page); > if (!memcg) > return 0; > > -- > 1.8.3.1 -- Michal Hocko SUSE Labs