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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 53454C4338F for ; Tue, 3 Aug 2021 12:02:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A85D060F0F for ; Tue, 3 Aug 2021 12:02:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A85D060F0F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 4DEF06B0033; Tue, 3 Aug 2021 08:02:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 48F796B0036; Tue, 3 Aug 2021 08:02:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 37E166B005D; Tue, 3 Aug 2021 08:02:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0192.hostedemail.com [216.40.44.192]) by kanga.kvack.org (Postfix) with ESMTP id 1E0926B0033 for ; Tue, 3 Aug 2021 08:02:24 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id CAFCE181AEF3E for ; Tue, 3 Aug 2021 12:02:23 +0000 (UTC) X-FDA: 78433631766.10.49A46E6 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf10.hostedemail.com (Postfix) with ESMTP id 74F5A600AA28 for ; Tue, 3 Aug 2021 12:02:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=fqSHKnZTWGmS5kpvDXOu7rtMWWiRcadlbYWKyvYr8uE=; b=AByIIbSWvwGMZvxM4zF6gD7Inx jFfSI9m+8WJwHEiJftOedg2iujxIBsRKVVoGpDcsrr0NOGYSrbhkvXBNfCinaPC6vpHr6WKCHdLwe 5ewP37RIvvFlFjWRIVxUD1/2o8ZjKGGiHzasgOe/UUxuoasZAg2QNj+QwOd3OZZX3lnAYXHIwWfyI 57l/JRA/gHSRLcY0AMWI/Pr43vtimbuy1GQ7WcZ4EHs337Oe2RlvWXlPOTRXdinSvudvbgLwVFgBO pqIOlsdSwyIXo2NNYvrtSXkKz1Lkhz4S+c77e5BtgTq6Jh9QRslIHH71Qv6Dv3P+FvukFeoyqWqiN 8Y7k0f6Q==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mAt6b-004c1q-UL; Tue, 03 Aug 2021 12:01:20 +0000 Date: Tue, 3 Aug 2021 13:01:09 +0100 From: Matthew Wilcox To: "Huang, Ying" Cc: Hugh Dickins , Andrew Morton , David Hildenbrand , Yang Shi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Miaohe Lin , Johannes Weiner , Michal Hocko , Joonsoo Kim , Minchan Kim Subject: Re: [PATCH] mm,shmem: Fix a typo in shmem_swapin_page() Message-ID: References: <20210723080000.93953-1-ying.huang@intel.com> <24187e5e-069-9f3f-cefe-39ac70783753@google.com> <8735rr54i9.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8735rr54i9.fsf@yhuang6-desk2.ccr.corp.intel.com> Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=AByIIbSW; dmarc=none; spf=none (imf10.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Stat-Signature: i7cb19zf8okwq8fzpn44a1fy8omhaqp3 X-Rspamd-Queue-Id: 74F5A600AA28 X-Rspamd-Server: rspam01 X-HE-Tag: 1627992143-751413 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 Tue, Aug 03, 2021 at 04:14:38PM +0800, Huang, Ying wrote: > Matthew Wilcox writes: > > But I REALLY REALLY REALLY want a reproducer. Right now, I have a hard > > time believing this, or any of the other races can really happen. > > I think the race is only theoretical too. Firstly, swapoff is a rare > operations in practice; secondly, the race window is really small. So do something to provoke it. Widen the window. Put an msleep(1000) between *pagep = NULL and the call to get_swap_device(). That's assuming that the swapon/swapoff loop that I proposed doesn't work. Did you try it?