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=-11.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,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 AC289C4363D for ; Thu, 24 Sep 2020 20:04:43 +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 C816B23899 for ; Thu, 24 Sep 2020 20:04:42 +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="FAtcbRuX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C816B23899 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]:34834 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLXTt-0003h5-L9 for qemu-devel@archiver.kernel.org; Thu, 24 Sep 2020 16:04:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58078) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLXRO-0002aQ-LH for qemu-devel@nongnu.org; Thu, 24 Sep 2020 16:02:09 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33198) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLXRM-0002bY-83 for qemu-devel@nongnu.org; Thu, 24 Sep 2020 16:02:06 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600977723; 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=y85ZHlPSu0LbWcyK0kASihR4L/4cljs70hwchn0FjHc=; b=FAtcbRuXi1JdzMGXbxl9aOYnGejMFziZK/aHjCzSMLvV+LuyIZ8rGFnSGV44pqTVRWAlPa DxxyBPbeYOvZbQ+YyEQn0nQvyIOLoZTXn6P5Q8rLmrFXdJa1ICZwsKB7HY2BTqC+ZZUaLY ygab7byaUmmGIzfP69oi3qO83vy5uG8= 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-263-voM5z1hWN1CaFfCZ6R9eEA-1; Thu, 24 Sep 2020 16:01:58 -0400 X-MC-Unique: voM5z1hWN1CaFfCZ6R9eEA-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 14A42801002; Thu, 24 Sep 2020 20:01:57 +0000 (UTC) Received: from [10.3.114.148] (ovpn-114-148.phx2.redhat.com [10.3.114.148]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3B3487368C; Thu, 24 Sep 2020 20:01:52 +0000 (UTC) Subject: Re: [PATCH v7 1/5] block/io: fix bdrv_co_block_status_above To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200924194003.22080-1-vsementsov@virtuozzo.com> <20200924194003.22080-2-vsementsov@virtuozzo.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <5dc62204-a1fe-1a94-144d-86c89a5f2bc8@redhat.com> Date: Thu, 24 Sep 2020 15:01:51 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200924194003.22080-2-vsementsov@virtuozzo.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; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/22 23:02:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.214, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=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: fam@euphon.net, kwolf@redhat.com, Alberto Garcia , 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 9/24/20 2:39 PM, 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 > Reviewed-by: Alberto Garcia > --- > block/io.c | 68 ++++++++++++++++++++++++++++++++++++++++----------- > block/qcow2.c | 16 ++++++++++-- > 2 files changed, 68 insertions(+), 16 deletions(-) > > diff --git a/block/io.c b/block/io.c > index 449b99b92c..4697e67a85 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -2350,34 +2350,74 @@ bdrv_co_common_block_status_above(BlockDriverState *bs, > int64_t *map, > BlockDriverState **file) > { > + int ret; > BlockDriverState *p; > - int ret = 0; The shuffle of these lines is odd, but not a show-stopper. The new flow is definitely easier to read. Thanks for doing this! > +++ b/block/qcow2.c > @@ -3860,8 +3860,20 @@ 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 We're inconsistent on whether we spell the noun 'zeros' or 'zeroes'; but I don't care enough to make you change this. > + * example, zeros which come from the region which is unallocated in > + * the whole backing chain, and zeros which comes because of a short s/comes/come/ > + * backing 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, > Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org