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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 D8691C33CB7 for ; Mon, 20 Jan 2020 04:19:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A2E6C2073A for ; Mon, 20 Jan 2020 04:19:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2E6C2073A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 37EFC6B05A6; Sun, 19 Jan 2020 23:19:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 309D06B05A7; Sun, 19 Jan 2020 23:19:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1F7E46B05A8; Sun, 19 Jan 2020 23:19:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0228.hostedemail.com [216.40.44.228]) by kanga.kvack.org (Postfix) with ESMTP id 093656B05A6 for ; Sun, 19 Jan 2020 23:19:15 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 9BDDE2490 for ; Mon, 20 Jan 2020 04:19:14 +0000 (UTC) X-FDA: 76396707828.11.grape74_8ac9504887d40 X-HE-Tag: grape74_8ac9504887d40 X-Filterd-Recvd-Size: 5456 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Mon, 20 Jan 2020 04:19:13 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D6FF531B; Sun, 19 Jan 2020 20:19:12 -0800 (PST) Received: from [10.162.16.78] (p8cg001049571a15.blr.arm.com [10.162.16.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 37C7F3F52E; Sun, 19 Jan 2020 20:19:10 -0800 (PST) Subject: Re: [PATCH -mm] mm/page_isolation: fix potential warning from user To: Qian Cai , akpm@linux-foundation.org Cc: mhocko@kernel.org, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200120034252.1558-1-cai@lca.pw> From: Anshuman Khandual Message-ID: <91ba5997-b227-7ae2-8459-310e18b9bb87@arm.com> Date: Mon, 20 Jan 2020 09:50:33 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200120034252.1558-1-cai@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: Hello Qian, On 01/20/2020 09:12 AM, Qian Cai wrote: > It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE) > from the offlining path, but should avoid triggering it from userspace, > i.e, from is_mem_section_removable(). Could you elaborate why it makes sense not to warn about an unmovable ZONE_MOVABLE page when an user tries to query about a memory block device's movability through sysfs ? > > While at it, simplify the code a bit by removing an unnecessary jump > label and a local variable, so set_migratetype_isolate() could really > return a bool. > > Suggested-by: Michal Hocko > Signed-off-by: Qian Cai > --- > mm/page_alloc.c | 11 ++++------- > mm/page_isolation.c | 31 ++++++++++++++++++------------- > 2 files changed, 22 insertions(+), 20 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 621716a25639..3c4eb750a199 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8231,7 +8231,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, > if (is_migrate_cma(migratetype)) > return NULL; > > - goto unmovable; > + return page; > } > > for (; iter < pageblock_nr_pages; iter++) { > @@ -8241,7 +8241,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, > page = pfn_to_page(pfn + iter); > > if (PageReserved(page)) > - goto unmovable; > + return page; > > /* > * If the zone is movable and we have ruled out all reserved > @@ -8261,7 +8261,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, > unsigned int skip_pages; > > if (!hugepage_migration_supported(page_hstate(head))) > - goto unmovable; > + return page; > > skip_pages = compound_nr(head) - (page - head); > iter += skip_pages - 1; > @@ -8303,12 +8303,9 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, > * is set to both of a memory hole page and a _used_ kernel > * page at boot. > */ > - goto unmovable; > + return page; > } > return NULL; > -unmovable: > - WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE); > - return pfn_to_page(pfn + iter); > } > > #ifdef CONFIG_CONTIG_ALLOC > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index e70586523ca3..97f673d5fefa 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -15,12 +15,12 @@ > #define CREATE_TRACE_POINTS > #include > > -static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags) > +static bool set_migratetype_isolate(struct page *page, int migratetype, > + int isol_flags) > { > - struct page *unmovable = NULL; > + struct page *unmovable = ERR_PTR(-EBUSY); > struct zone *zone; > unsigned long flags; > - int ret = -EBUSY; > > zone = page_zone(page); > > @@ -49,21 +49,26 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ > NULL); > > __mod_zone_freepage_state(zone, -nr_pages, mt); > - ret = 0; > } > > out: > spin_unlock_irqrestore(&zone->lock, flags); > - if (!ret) > + > + if (!unmovable) { > drain_all_pages(zone); > - else if ((isol_flags & REPORT_FAILURE) && unmovable) > - /* > - * printk() with zone->lock held will guarantee to trigger a > - * lockdep splat, so defer it here. > - */ > - dump_page(unmovable, "unmovable page"); > - > - return ret; > + } else { > + if (isol_flags & MEMORY_OFFLINE) > + WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);> + > + if ((isol_flags & REPORT_FAILURE) && !IS_ERR(unmovable)) > + /* > + * printk() with zone->lock held will likely trigger a > + * lockdep splat, so defer it here. > + */ > + dump_page(unmovable, "unmovable page"); > + } > + > + return !!unmovable; > } > > static void unset_migratetype_isolate(struct page *page, unsigned migratetype) set_migratetype_isolate() gets called from CMA as well as HugeTLB allocation paths, so its not only during offline. Hence the commit message should be changed to reflect this. - Anshuman >