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,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 472E4C433DF for ; Wed, 14 Oct 2020 13:05:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D543221527 for ; Wed, 14 Oct 2020 13:05:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="Tte/tOrj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731061AbgJNNFx (ORCPT ); Wed, 14 Oct 2020 09:05:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727141AbgJNNFw (ORCPT ); Wed, 14 Oct 2020 09:05:52 -0400 Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7314FC061755 for ; Wed, 14 Oct 2020 06:05:52 -0700 (PDT) Received: by mail-lj1-x241.google.com with SMTP id c21so3152205ljj.0 for ; Wed, 14 Oct 2020 06:05:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=4ZpNEpwEuFA9Rfuw8aSUEHfgR5iSTqvnZX1G9kxgifM=; b=Tte/tOrj3c7eCfHcXm4ClATrY0EmDpKA48oz5D3m0/1p3dkxXHSfod3UKUn7LMxKlM r6IoMLOJlWrhtvJa3IgB0aYPRqaCiuaYK+UYZgVjPJ9htrgHoqdWFr4bQc4GGldcyYwc FTy7Rh3n1xWPTAh8yUbnwnE6+43zXN/iVmZCPFftSwKJiwMjvuVjYtT+4lfKa0C4C1mi nRHdoVP/J9d/lJP5HLeZ8U76fWQpXP2GjiYjZY24a3OaAWJdO84Q01ECLLu7rTM3654D ClJ48Z6CqXb4Vu4aHNbWk2gWkafO6kJ/lRNFl0GGzjTjKPGU7M35xTkxT4r79Bp8kw9x U5TA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=4ZpNEpwEuFA9Rfuw8aSUEHfgR5iSTqvnZX1G9kxgifM=; b=fVEY8779PzEwsclB4svyD5WggQfSwB4iOcx8lPAWAlBp6TcWF0TCktJC/NOJOAOPLd ruWWKe3KMhYsNoYY2ald12f5JgLPd/PTAB4MAWROmfhuF1AweyW4MapXu5mjYANKzus8 LQds9MhUhUKO7xb6KywybwDmxPp7g3ycFOWe6vN4aAIUj/a6QLPmqx9Bux5ub1KgejJW i4dM3zOeP70h8I+1dqPVbfhzawT9fLtZ9GNNTOzO3p3+UC+OfC/tMyXFLTJm29nRwz/i my/d2aSSwdj6Y7Em6Akdi11NzO5EHQ6b/TY/hgpRue53P50vHIN9BbH8RADAS/XHpJev 1Uyg== X-Gm-Message-State: AOAM531Dx/U7oIZY/rlZLS5inFa1SNODlcgeGutnPA1W8aSegNJVc9Fd SIptt6O13Q3ON0nBoWV+fI8kvQ== X-Google-Smtp-Source: ABdhPJxjPAif0rDRfil1S4kF1FE0lGY1f39gKXlMRTWe6gjf0jnvjuHXT2t5WekJ69UjCNHZCpi2XQ== X-Received: by 2002:a2e:7d0e:: with SMTP id y14mr1699656ljc.254.1602680750926; Wed, 14 Oct 2020 06:05:50 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id p7sm1113688lfc.299.2020.10.14.06.05.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2020 06:05:50 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id 4EC9A1035E0; Wed, 14 Oct 2020 16:05:55 +0300 (+03) Date: Wed, 14 Oct 2020 16:05:55 +0300 From: "Kirill A. Shutemov" To: Linus Torvalds Cc: Hugh Dickins , Matthew Wilcox , Linux-MM , Andrew Morton , linux-fsdevel , Amir Goldstein Subject: Re: [PATCH 0/4] Some more lock_page work.. Message-ID: <20201014130555.kdbxyavqoyfnpos3@box> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Oct 13, 2020 at 01:03:30PM -0700, Linus Torvalds wrote: > On Tue, Oct 13, 2020 at 12:59 PM Linus Torvalds > wrote: > > > > Comments? So we remove strict serialization against truncation in filemap_map_pages() if the mapping is private. IIUC, we can end up with a page with ->mapping == NULL set up in a PTE for such mappings. The "page->mapping != mapping" check makes the race window smaller, but doesn't remove it. I'm not sure all codepaths are fine with this. For instance, looks like migration will back off such pages: __unmap_and_move() doesn't know how to deal with mapped pages with ->mapping == NULL. Yes, it is not crash, but still... Do I miss something? -- Kirill A. Shutemov