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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 70FACC2D0E4 for ; Mon, 23 Nov 2020 18:25:22 +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 A5A0C2080A for ; Mon, 23 Nov 2020 18:25:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fXKgoS3c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5A0C2080A 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]:35984 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1khGWe-0004ND-Lx for qemu-devel@archiver.kernel.org; Mon, 23 Nov 2020 13:25:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:58024) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1khGV9-00030d-9K for qemu-devel@nongnu.org; Mon, 23 Nov 2020 13:23:47 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:56752) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1khGV7-0003zC-Ji for qemu-devel@nongnu.org; Mon, 23 Nov 2020 13:23:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606155824; 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=FRS/abP6x0NA22Yn+D+ZEef2qNDdTH1GLQLJ2kgefek=; b=fXKgoS3cjUDd+2Z/cI4ladsAbka2/QSsnXfGdCmW9qdYY/G8sNzNq7vfLvps3KHvil8pxP 5ddtXb1iZTcvDMj9lYNjDnkVh7RWkCupic6B0vvE+EZEs7qqNvbcs7QjEb6zvqU121wnkc DQwD2m0x5IhFLw16NPHStMy+/RGZ8os= 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-518-VKQ2bQU_N5OoTXfJQd8DEg-1; Mon, 23 Nov 2020 13:23:42 -0500 X-MC-Unique: VKQ2bQU_N5OoTXfJQd8DEg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6712C18C43C1; Mon, 23 Nov 2020 18:23:41 +0000 (UTC) Received: from starship (unknown [10.35.206.216]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4F22A6062F; Mon, 23 Nov 2020 18:23:37 +0000 (UTC) Message-ID: Subject: Re: [PATCH 1/1] Fix qcow2 corruption on discard From: Maxim Levitsky To: Alberto Garcia , Kevin Wolf Date: Mon, 23 Nov 2020 20:23:36 +0200 In-Reply-To: References: <20201123154929.330338-1-mlevitsk@redhat.com> <20201123154929.330338-2-mlevitsk@redhat.com> <20201123160941.GD5317@merkur.fritz.box> User-Agent: Evolution 3.36.3 (3.36.3-1.fc32) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=mlevitsk@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: vsementsov@virtuozzo.com, qemu-block@nongnu.org, zhang_youjia@126.com, qemu-devel@nongnu.org, Max Reitz , andrey.shinkevich@virtuozzo.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 2020-11-23 at 19:20 +0100, Alberto Garcia wrote: > On Mon 23 Nov 2020 05:09:41 PM CET, Kevin Wolf wrote: > > > Commit 205fa50750 ("qcow2: Add subcluster support to zero_in_l2_slice()") > > > introduced a subtle change to code in zero_in_l2_slice: > > > > > > It swapped the order of > > > > > > 1. qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); > > > 2. set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO); > > > 3. qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); > > > > > > To > > > > > > 1. qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); > > > 2. qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); > > > 3. set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO); > > Ouch :( Good catch! > > > > - qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); > > > if (unmap) { > > > qcow2_free_any_cluster(bs, old_l2_entry, QCOW2_DISCARD_REQUEST); > > > } > > > set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry); > > > + qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); > > > > Good catch, but I think your order is wrong, too. We need the original > > order from before 205fa50750: > > > > 1. qcow2_cache_entry_mark_dirty() > > set_l2_entry() + set_l2_bitmap() > > > > 2. qcow2_free_any_cluster() > > I agree with Kevin on this. I also agree, I haven't thought about this. Best regards, Maxim Levitsky > > Berto >