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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 69C1BC433ED for ; Tue, 13 Apr 2021 13:46:51 +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 D339C611F0 for ; Tue, 13 Apr 2021 13:46:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D339C611F0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49610 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lWJNR-0008FK-VM for qemu-devel@archiver.kernel.org; Tue, 13 Apr 2021 09:46:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53124) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWJKR-0006CU-So for qemu-devel@nongnu.org; Tue, 13 Apr 2021 09:43:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28429) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWJKP-0007j9-5S for qemu-devel@nongnu.org; Tue, 13 Apr 2021 09:43:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618321420; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fEDmTaI9cHDNJ/8GO/HMIGBKm66AEMkxQW/a1ggHvoU=; b=DHJ1WGlLdlwOpnQb/9D7780hNSWzBeAOnDa5GuNJlR10mGij8WMHKJMJBZ6jp9NQtk46Nc UGXMZW0lg3dUNWW9w20nH0dTL9uNoeRCEbBuNFGaeRJ8ejX+m2rcEGPQ1za8eTnCDnj6Bu 8lzYM+T7558rf3TSLUPvqk8HYBnGOsk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-428--N2tHZcvPoSJW8Ob8ZKITQ-1; Tue, 13 Apr 2021 09:43:37 -0400 X-MC-Unique: -N2tHZcvPoSJW8Ob8ZKITQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD202188352E; Tue, 13 Apr 2021 13:43:36 +0000 (UTC) Received: from [10.3.114.86] (ovpn-114-86.phx2.redhat.com [10.3.114.86]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 85EA260DA0; Tue, 13 Apr 2021 13:43:36 +0000 (UTC) Subject: Re: [PATCH 2/2] qemu-img convert: Unshare write permission for source To: Kevin Wolf , qemu-block@nongnu.org References: <20210413132324.24043-1-kwolf@redhat.com> <20210413132324.24043-3-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <5edcdaf9-2133-b426-82bb-8849264ff4fd@redhat.com> Date: Tue, 13 Apr 2021 08:43:35 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210413132324.24043-3-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: , Cc: xuwei@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/13/21 8:23 AM, Kevin Wolf wrote: > For a successful conversion of an image, we must make sure that its > content doesn't change during the conversion. > > A special case of this is using the same image file both as the source > and as the destination. If both input and output format are raw, the > operation would just be useless work, with other formats it is a sure > way to destroy the image. This will now fail because the image file > can't be opened a second time for the output when opening it for the > input has already acquired file locks to unshare BLK_PERM_WRITE. > > Nevertheless, if there is some reason in a special case why it is > actually okay to allow writes to the image while it is being converted, > -U can still be used to force sharing all permissions. > > Note that for most image formats, BLK_PERM_WRITE would already be > unshared by the format driver, so this only really makes a difference > for raw source images (but any output format). > > Reported-by: Xueqiang Wei > Signed-off-by: Kevin Wolf > --- > qemu-img.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Eric Blake > > diff --git a/qemu-img.c b/qemu-img.c > index babb5573ab..a5993682aa 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -2146,7 +2146,7 @@ static void set_rate_limit(BlockBackend *blk, int64_t rate_limit) > > static int img_convert(int argc, char **argv) > { > - int c, bs_i, flags, src_flags = 0; > + int c, bs_i, flags, src_flags = BDRV_O_NO_SHARE; > const char *fmt = NULL, *out_fmt = NULL, *cache = "unsafe", > *src_cache = BDRV_DEFAULT_CACHE, *out_baseimg = NULL, > *out_filename, *out_baseimg_param, *snapshot_name = NULL; > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org