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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 0F3D1C433E0 for ; Wed, 20 May 2020 14:39:27 +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 BE9EF207C4 for ; Wed, 20 May 2020 14:39:26 +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="ab971ELq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE9EF207C4 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]:50076 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jbPsU-0008V5-0D for qemu-devel@archiver.kernel.org; Wed, 20 May 2020 10:39:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60444) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jbPrt-000810-IB for qemu-devel@nongnu.org; Wed, 20 May 2020 10:38:49 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:26173 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jbPrr-0001KF-61 for qemu-devel@nongnu.org; Wed, 20 May 2020 10:38:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589985525; 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=L4SU0WetqPbmum2RDmvGMrtIYEQl2w7sZJXKe381jlI=; b=ab971ELqJeEU3om4g06DA4GcaHxKM8II5LbreCeEUtsxand9eAFPKsVvKoAfaOOXPPEypb GZqCchYuc8U6duJZWt4QrO0l5BjWr/iRZqPc5lj1V19OrAdewdm0/s/BgHhR3zeslO81j7 Ry2QcVOjFo3hNgN5EzjN1cm8NnbDPfI= 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-401-BISD0DqaOiSfTVUOYPKB0w-1; Wed, 20 May 2020 10:38:36 -0400 X-MC-Unique: BISD0DqaOiSfTVUOYPKB0w-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 375AC107ACF9; Wed, 20 May 2020 14:38:35 +0000 (UTC) Received: from [10.3.112.88] (ovpn-112-88.phx2.redhat.com [10.3.112.88]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 83F5F1057FD8; Wed, 20 May 2020 14:38:31 +0000 (UTC) Subject: Re: [PATCH v3 1/5] block/io: fix bdrv_co_block_status_above To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200520083520.25793-1-vsementsov@virtuozzo.com> <20200520083520.25793-2-vsementsov@virtuozzo.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <1dfda9f1-48cf-236c-65eb-7afc5daaa77c@redhat.com> Date: Wed, 20 May 2020 09:38:30 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200520083520.25793-2-vsementsov@virtuozzo.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/20 04:09:34 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: kwolf@redhat.com, fam@euphon.net, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/20/20 3:35 AM, Vladimir Sementsov-Ogievskiy wrote: > bdrv_co_block_status_above has several design problems with handling > short backing files: > > 1. With want_zeros=true, it may return ret with BDRV_BLOCK_ZERO but > without BDRV_BLOCK_ALLOCATED flag, when actually short backing file > which produces these after-EOF zeros is inside requested backing > sequence. > > 2. With want_zero=false, it may return pnum=0 prior to actual EOF, > because of EOF of short backing file. > > Fix these things, making logic about short backing files clearer. > > With fixed bdrv_block_status_above we also have to improve is_zero in > qcow2 code, otherwise iotest 154 will fail, because with this patch we > stop to merge zeros of different types (produced by fully unallocated > in the whole backing chain regions vs produced by short backing files). > > Note also, that this patch leaves for another day the general problem > around block-status: misuse of BDRV_BLOCK_ALLOCATED as is-fs-allocated > vs go-to-backing. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block/io.c | 39 ++++++++++++++++++++++++++++++--------- > block/qcow2.c | 16 ++++++++++++++-- > 2 files changed, 44 insertions(+), 11 deletions(-) Reviewed-by: Eric Blake > +++ b/block/qcow2.c > @@ -3827,8 +3827,20 @@ static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes) > if (!bytes) { > return true; > } > - res = bdrv_block_status_above(bs, NULL, offset, bytes, &nr, NULL, NULL); > - return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == bytes; > + > + /* > + * bdrv_block_status_above doesn't merge different types of zeros, for > + * example, zeros which comes from the region which is unallocated in s/comes/come/ > + * the whole backing chain, and zeros which comes because of short backing and again, also s/of/of a/ > + * file. So, we need a loop. > + */ > + do { > + res = bdrv_block_status_above(bs, NULL, offset, bytes, &nr, NULL, NULL); > + offset += nr; > + bytes -= nr; > + } while (res >= 0 && (res & BDRV_BLOCK_ZERO) && nr && bytes); > + > + return res >= 0 && (res & BDRV_BLOCK_ZERO) && bytes == 0; > } > > static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs, > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org