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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 A3992C33CA1 for ; Mon, 20 Jan 2020 13:54:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78073217F4 for ; Mon, 20 Jan 2020 13:54:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="G/5kXvqR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726876AbgATNyk (ORCPT ); Mon, 20 Jan 2020 08:54:40 -0500 Received: from mail-io1-f68.google.com ([209.85.166.68]:34560 "EHLO mail-io1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgATNyk (ORCPT ); Mon, 20 Jan 2020 08:54:40 -0500 Received: by mail-io1-f68.google.com with SMTP id z193so33746575iof.1; Mon, 20 Jan 2020 05:54:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=A9BomRl8cOqD5J6VizMdaO4qtRV2qD8Sxz+xVA/FCwY=; b=G/5kXvqRu1WxCz3g1HVe00s3Xff3vBvEvqpGz/eGT7WcOdxfQsr01Tnwu4vt9jApWy nuSgta0xztw4dSoRI2mZFEHqyW0y5wEsRaQhdKbbPmv1ilZuPg75Z9DE4ZVanolNYjzi Zcm9L7afSxsLPz+6ldqFYEaaNT1ioxglNJI6R/pIY6//qpaavBYlUOyZrtyvAkukg0Bo NVlO3lASc5pCd7mP2WWe80vY/l+wAwtoBrz8VnZnFNXKU8nE3XboNJce7rMhXYskE8dk xuaTwBUJQcqzQhSq3F0dtePOpn8bvY6DCDsjl8lAUK3myukdsMTYGePZp32rAhq4lZR+ a+Kg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=A9BomRl8cOqD5J6VizMdaO4qtRV2qD8Sxz+xVA/FCwY=; b=XzKIbHPGQs+t8gsjFsClrM3Mv9CjJDjRk1sItNzrraMmJDhAPY7QPXekCIsgOQ2JXc Ftv9RhSCWTKUREQLvfNh1qhbH6IXmM5mXPb8uVUvujR+U7MQO37V2XuxLX+S2Qh7tAz1 HP6GMnCY+YATeBAgwqHGgYpAAWVgqIW5Gi+6HtRWifYE8kustA89aaUVXIXsx1knFZ3q YEDx1+PbK9qAFTjcGf++8K4t5f35LFpQAMGk01cP/shBgQsDPdizES7V+xYKMFBZxnTG qXu+xj4iPh6bQqHO5XUWbZClzaI3ObGZMMpsyrB5UE1G08aloMfQVJcml28IjsOrYddA vfzw== X-Gm-Message-State: APjAAAWcafn4X9wclCHgIir7qFkYhUra7DqJLLuw/ZLQY4QwlWn+inc2 5oKqIBUrGEJ4rZyQ9L4rlk8C3yiPjcTOp0dRObE= X-Google-Smtp-Source: APXvYqzJYVTTnME9AcE53rOwW95R5jUMm4G5XkLB9kyPpoSSXoCZtLZqNzywfWbx31CI1a8KPWD3R6NlSsDblYCZr8Q= X-Received: by 2002:a6b:f214:: with SMTP id q20mr43607002ioh.137.1579528479611; Mon, 20 Jan 2020 05:54:39 -0800 (PST) MIME-Version: 1.0 References: <20190829131034.10563-1-jack@suse.cz> <20200120120333.GG19861@quack2.suse.cz> In-Reply-To: <20200120120333.GG19861@quack2.suse.cz> From: Amir Goldstein Date: Mon, 20 Jan 2020 15:54:28 +0200 Message-ID: Subject: Re: [PATCH 0/3 v2] xfs: Fix races between readahead and hole punching To: Jan Kara Cc: linux-xfs , Linux MM , "Darrick J. Wong" , Boaz Harrosh , linux-fsdevel , Matthew Wilcox , Jens Axboe , Kent Overstreet Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 20, 2020 at 2:03 PM Jan Kara wrote: > > Hi Amir! > > On Fri 17-01-20 12:50:58, Amir Goldstein wrote: > > On Thu, Aug 29, 2019 at 4:10 PM Jan Kara wrote: > > > > > > Hello, > > > > > > this is a patch series that addresses a possible race between readahead and > > > hole punching Amir has discovered [1]. The first patch makes madvise(2) to > > > handle readahead requests through fadvise infrastructure, the third patch > > > then adds necessary locking to XFS to protect against the race. Note that > > > other filesystems need similar protections but e.g. in case of ext4 it isn't > > > so simple without seriously regressing mixed rw workload performance so > > > I'm pushing just xfs fix at this moment which is simple. > > > > > > > Could you give a quick status update about the state of this issue for > > ext4 and other fs. I remember some solutions were discussed. > > Shortly: I didn't get to this. I'm sorry :-|. I'll bump up a priority but I > can't promise anything at the moment. > > > Perhaps this could be a good topic for a cross track session in LSF/MM? > > Maybe although this is one of the cases where it's easy to chat about > possible solutions but somewhat tedious to write one so I'm not sure how > productive that would be. BTW my discussion with Kent [1] is in fact very > related to this problem (the interval lock he has is to stop exactly races > like this). > Well, I was mostly interested to know if there is an agreement on the way to solve the problem. If we need to discuss it to reach consensus than it might be a good topic for LSF/MM. If you already know what needs to be done, there is no need for a discussion. > > Aren't the challenges posed by this race also relevant for RWF_UNCACHED? > > Do you have anything particular in mind? I don't see how RWF_UNCACHED would > make this any better or worse than DIO / readahead... > Not better nor worse. I meant that RFW_UNCACHED is another case that would suffer the same races. Thanks, Amir.