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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 5088AC169C4 for ; Wed, 6 Feb 2019 18:52:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1DEB1218D9 for ; Wed, 6 Feb 2019 18:52:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="UeDKl0Kc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727601AbfBFSwj (ORCPT ); Wed, 6 Feb 2019 13:52:39 -0500 Received: from mail-pl1-f172.google.com ([209.85.214.172]:46324 "EHLO mail-pl1-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727198AbfBFSwf (ORCPT ); Wed, 6 Feb 2019 13:52:35 -0500 Received: by mail-pl1-f172.google.com with SMTP id o6so3480865pls.13 for ; Wed, 06 Feb 2019 10:52:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=7kkFe7VdBrYTS6xqWBGiPDeMMQbpDhl/VS6LUReyUBQ=; b=UeDKl0KcK9Kh84HZYa+Kne8AvZDEZqJjKRI+db+e6qNigCbKK9k11LicvJ+v6NwMTL ikRkpAlhvpX+VwaJ5A5gEjhJJXGFoq3jYEi61RKLq4bHORjLX84v80uvJkRxuk3lIuPg qFRlyaK6OFtCH5ONOXEE/30mb9WgiDfve0J3SRETcJD0rNpKRgy1TX2J5tsyhLk0h0VD E7PqtsWopoi/2QtU/oSqwAPBSJKr25LnINrMPtLfGvojjf3wUW76x/pbiHk+Ro2ikOTW J5/jh+VVhlV11sOMR+jf+9CM9/YgCQWiKt4POuKeRh6GzUWk0/q9DXC6VSo2sjfDS0zZ pBDQ== 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:user-agent; bh=7kkFe7VdBrYTS6xqWBGiPDeMMQbpDhl/VS6LUReyUBQ=; b=N5HIG14gh+zabYPWL+n0zZuWhCkP9d21oF2C59VT7QwWlC6w11xKkDSdN91J37kh+G 9qkW2kjxKcmTcE6+Yi482cOhg85LQv3fK2QPiqz6eOs0voiqXHgauqNSMaNatWAM2zkC zaByZfKuaeV+4JCGQG9migRqPDTaoHD5CAq8UQ1NjSy6+vhrskJwNanQllV6ypeGd5a8 bM2VjrmCMCaiQsNQPWXE7drQQ9ciCYHk+jllGM2Pci8ksVfk1ps2WASFSSmZ+i5ds1tK 6GbKsz7pYHQVGIvG7gnwsg2Oj9UoHIVE6i/8v1EQheGE/smjVB3Dxp2bkFBUd/qXaswk Mk5A== X-Gm-Message-State: AHQUAuYdMgnbqPzn0haltYxkZJA5HvazCdu51oM/4qUI16yj9mEYxEwH uR7k3l0eQatcAvT1g9SNu9tiAm0XCDg= X-Google-Smtp-Source: AHgI3IatX2FVUNy8ZnyYH2Fw5fpeSFfpCk+VVQB6B+D6cnVwuZwhknf53tZzWm/cIRrvMjAPeVeTaw== X-Received: by 2002:a17:902:8497:: with SMTP id c23mr12071867plo.64.1549479155012; Wed, 06 Feb 2019 10:52:35 -0800 (PST) Received: from ziepe.ca (S010614cc2056d97f.ed.shawcable.net. [174.3.196.123]) by smtp.gmail.com with ESMTPSA id 64sm9553472pff.101.2019.02.06.10.52.34 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 06 Feb 2019 10:52:34 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1grSJF-0004c2-Pk; Wed, 06 Feb 2019 11:52:33 -0700 Date: Wed, 6 Feb 2019 11:52:33 -0700 From: Jason Gunthorpe To: Matthew Wilcox Cc: Doug Ledford , Jan Kara , Ira Weiny , lsf-pc@lists.linux-foundation.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard , Jerome Glisse , Dan Williams , Dave Chinner , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190206185233.GE12227@ziepe.ca> References: <20190205175059.GB21617@iweiny-DESK2.sc.intel.com> <20190206095000.GA12006@quack2.suse.cz> <20190206173114.GB12227@ziepe.ca> <20190206175233.GN21860@bombadil.infradead.org> <47820c4d696aee41225854071ec73373a273fd4a.camel@redhat.com> <20190206183503.GO21860@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190206183503.GO21860@bombadil.infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 06, 2019 at 10:35:04AM -0800, Matthew Wilcox wrote: > > Admittedly, I'm coming in late to this conversation, but did I miss the > > portion where that alternative was ruled out? > > That's my preferred option too, but the preponderance of opinion leans > towards "We can't give people a way to make files un-truncatable". I haven't heard an explanation why blocking ftruncate is worse than giving people a way to break RDMA using process by calling ftruncate?? Isn't it exactly the same argument the other way? Jason