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=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 5420DC4727F for ; Mon, 28 Sep 2020 23:52:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C44D2207D8 for ; Mon, 28 Sep 2020 23:52:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="NC7nJD6u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C44D2207D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id ECBED6B005C; Mon, 28 Sep 2020 19:52:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E7CE96B005D; Mon, 28 Sep 2020 19:52:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D92DB6B0062; Mon, 28 Sep 2020 19:52:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0027.hostedemail.com [216.40.44.27]) by kanga.kvack.org (Postfix) with ESMTP id C47476B005C for ; Mon, 28 Sep 2020 19:52:17 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 7A41F180AD807 for ; Mon, 28 Sep 2020 23:52:17 +0000 (UTC) X-FDA: 77314121514.29.sky01_631183427185 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin29.hostedemail.com (Postfix) with ESMTP id 542F918086CCB for ; Mon, 28 Sep 2020 23:52:17 +0000 (UTC) X-HE-Tag: sky01_631183427185 X-Filterd-Recvd-Size: 3976 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Mon, 28 Sep 2020 23:52:16 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A39B2207D8; Mon, 28 Sep 2020 23:52:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601337136; bh=wFhp55ulXjxuuIoaT0rVvAcVgZE0echpnHPUtNYAzCM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NC7nJD6uGd78qkf48jTtE1RBIgE33wxNfXuWqjZLRm5fsfTb4jyLY/LcVJzorvCkM 0pAWGrxMv1T5+gTxUUh6YrvU14dMc0NpQ3DwrrQskblkfs1LOGOAQaSISYnrXc2wwL iHtAqWUQVF1DR5P24hiEwrUkpRHgihEA0Ks0tUrY= Date: Mon, 28 Sep 2020 16:52:15 -0700 From: Andrew Morton To: js1304@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Vlastimil Babka , "Aneesh Kumar K . V" , Mel Gorman , kernel-team@lge.com, Joonsoo Kim Subject: Re: [PATCH v2 for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs Message-Id: <20200928165215.f46924bfff9a109131048f81@linux-foundation.org> In-Reply-To: <1601283046-15329-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1601283046-15329-1-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: On Mon, 28 Sep 2020 17:50:46 +0900 js1304@gmail.com wrote: > From: Joonsoo Kim > > memalloc_nocma_{save/restore} APIs can be used to skip page allocation > on CMA area, but, there is a missing case and the page on CMA area could > be allocated even if APIs are used. This patch handles this case to fix > the potential issue. > > Missing case is an allocation from the pcplist. MIGRATE_MOVABLE pcplist > could have the pages on CMA area so we need to skip it if ALLOC_CMA isn't > specified. Changelog doesn't describe the end-user visible effects of the bug. Please send this description? > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3367,9 +3367,16 @@ struct page *rmqueue(struct zone *preferred_zone, > struct page *page; > > if (likely(order == 0)) { > - page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, > + /* > + * MIGRATE_MOVABLE pcplist could have the pages on CMA area and > + * we need to skip it when CMA area isn't allowed. > + */ > + if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA || > + migratetype != MIGRATE_MOVABLE) { > + page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, > migratetype, alloc_flags); > - goto out; > + goto out; > + } > } > > /* We still really really don't want to be adding overhead to the page allocation hotpath for a really really obscure feature from a single callsite. Do we have an understanding of how many people's kernels are enabling CONFIG_CMA? I previously suggested retrying the allocation in __gup_longterm_locked() but you said "it cannot ensure that we eventually get the non-CMA page". Please explain why? What about manually emptying the pcplists beforehand? Or byassing the pcplists for this caller and calling __rmqueue() directly? > @@ -3381,7 +3388,7 @@ struct page *rmqueue(struct zone *preferred_zone, > > do { > page = NULL; > - if (alloc_flags & ALLOC_HARDER) { > + if (order > 0 && alloc_flags & ALLOC_HARDER) { > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > if (page) > trace_mm_page_alloc_zone_locked(page, order, migratetype); What does this hunk do?