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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 13317C433DB for ; Fri, 15 Jan 2021 20:38:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 75AB92313E for ; Fri, 15 Jan 2021 20:38:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 75AB92313E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CF8CD6B017E; Fri, 15 Jan 2021 15:38:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CAA7C6B01A1; Fri, 15 Jan 2021 15:38:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BBFD86B029E; Fri, 15 Jan 2021 15:38:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0006.hostedemail.com [216.40.44.6]) by kanga.kvack.org (Postfix) with ESMTP id A52556B017E for ; Fri, 15 Jan 2021 15:38:07 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6F5401810B330 for ; Fri, 15 Jan 2021 20:38:07 +0000 (UTC) X-FDA: 77709171414.17.hot54_5b0b73c27532 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 52336181D2075 for ; Fri, 15 Jan 2021 20:38:07 +0000 (UTC) X-HE-Tag: hot54_5b0b73c27532 X-Filterd-Recvd-Size: 2202 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Fri, 15 Jan 2021 20:38:06 +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 C1724ADC1; Fri, 15 Jan 2021 20:38:05 +0000 (UTC) Date: Fri, 15 Jan 2021 21:38:03 +0100 From: Oscar Salvador To: Mike Kravetz Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Naoya Horiguchi , Muchun Song , David Hildenbrand , Andrew Morton Subject: Re: [RFC PATCH 2/3] hugetlb: convert page_huge_active() to HPageMigratable flag Message-ID: <20210115203803.GB3322@localhost.localdomain> References: <20210111210152.118394-1-mike.kravetz@oracle.com> <20210111210152.118394-3-mike.kravetz@oracle.com> <20210115091755.GB4092@linux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Fri, Jan 15, 2021 at 09:43:36AM -0800, Mike Kravetz wrote: > > Before the page_huge_active() in scan_movable_pages() we have the > > if (!PageHuge(page)) check, but could it be that between that check and > > the page_huge_active(), the page gets dissolved, and so we are checking > > a wrong page[1]? Am I making sense? > > Yes, you are making sense. > > The reason I decided to drop the check is because it does not eliminate the > race. Even with that check in page_huge_active, the page could be dissolved > between that check and check of page[1]. There really is no way to eliminate > the race without holding a reference to the page (or hugetlb_lock). That > check in page_huge_active just shortens the race window. Yeah, you are right, the race already exists. Anyway, do_migrate_range should take care of making sure what it is handling, so I think we are good. -- Oscar Salvador SUSE L3