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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 36E5DC5DF60 for ; Thu, 7 Nov 2019 12:09:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 094D22166E for ; Thu, 7 Nov 2019 12:09:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 094D22166E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41436 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSgbm-0002Vc-8u for qemu-devel@archiver.kernel.org; Thu, 07 Nov 2019 07:09:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54948) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSgbA-00026q-Dr for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:09:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iSgb9-0003IJ-9t for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:09:12 -0500 Received: from mga18.intel.com ([134.134.136.126]:17657) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iSgb9-0003HB-2B for qemu-devel@nongnu.org; Thu, 07 Nov 2019 07:09:11 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Nov 2019 04:09:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,278,1569308400"; d="scan'208";a="206133579" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga006.jf.intel.com with ESMTP; 07 Nov 2019 04:09:07 -0800 Date: Thu, 7 Nov 2019 20:08:56 +0800 From: Wei Yang To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 1/2] migration/compress: compress QEMUFile is not writable Message-ID: <20191107120856.GB25593@richard> References: <20191012023932.1863-1-richardw.yang@linux.intel.com> <20191012023932.1863-2-richardw.yang@linux.intel.com> <20191107115910.GG2816@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191107115910.GG2816@work-vm> User-Agent: Mutt/1.9.4 (2018-02-28) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.126 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Cc: qemu-devel@nongnu.org, Wei Yang , quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Nov 07, 2019 at 11:59:10AM +0000, Dr. David Alan Gilbert wrote: >* Wei Yang (richardw.yang@linux.intel.com) wrote: >> We open a file with empty_ops for compress QEMUFile, which means this is >> not writable. > >That explanation sounds reasonable; but I'm confused by the history of >this; the code was added by Liang Li in : > > b3be289 qemu-file: Fix qemu_put_compression_data flaw > > ( https://www.mail-archive.com/qemu-devel@nongnu.org/msg368974.html ) > >with almost exactly the opposite argument; can we figure out why? > Hmm... sounds interesting. Toke a look into the change log, which says Current qemu_put_compression_data can only work with no writable QEMUFile, and can't work with the writable QEMUFile. But it does not provide any measure to prevent users from using it with a writable QEMUFile. We should fix this flaw to make it works with writable QEMUFile. While I don't see a chance to use writable QEMUFile. Do I miss something? >Dave > -- Wei Yang Help you, Help me