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 4D8DCC2D0A8 for ; Mon, 28 Sep 2020 23:52:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EFFD1208FE for ; Mon, 28 Sep 2020 23:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601337138; bh=wFhp55ulXjxuuIoaT0rVvAcVgZE0echpnHPUtNYAzCM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=v/GwEuvxJ9i2xl1wHqo5zg9kE9d+8DyP3PXF4VhnE8A2c1nbBhHgfg21EQ8Ma5xNI u/mxHVNHl2C4FmphnvSyhz7JwjbOaol6iS7rNiOmaDybiDXxiCu1G7kumKu4ZQ4mR4 Wi0P6hP1LBVLpj+xYUhTidOyO+wGJAF7mJgYuSQk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727024AbgI1XwQ (ORCPT ); Mon, 28 Sep 2020 19:52:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:48802 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726969AbgI1XwQ (ORCPT ); Mon, 28 Sep 2020 19:52:16 -0400 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?