From nobody Sun Feb 8 14:52:39 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1555343843; cv=none; d=zoho.com; s=zohoarc; b=brN1nhtXFbvBteltlZ9wmInUGql2ScRKR+SNp/vQdmJV8nx0jSKJ3N+i+aBzvfoYBqY5pEa4Kv9AUV9LxDbV7tJd6kk96W1S9wta3L3owdW4Yyum4pbtLuu3iwQx4iyXX5ZrC9GJJB522Gi0ZILBCZc5XBv77doj7VmwXZS22Qc= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1555343843; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=r8W0VB4vIlo/FQ3W3B4eMUP0OkIqN50/BbG9cw+ja5w=; b=ldC6LsEXt/A8Gjc2d55lLaOTpfIrYb9xwFjDkW7yKPEdW0NEdUeuPlAqahcdzdn4AWfnOnXUAN0oeuUZDfP/XFH01bUfiZ4ScEQ+3lPP4OsJj7ciSh/MY998Mi57sp0RUEvZ4WQgyvkQGIrbHvbV0wbUo+gXka0xTK4xaMbnSuo= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1555343843432833.994128371748; Mon, 15 Apr 2019 08:57:23 -0700 (PDT) Received: from localhost ([127.0.0.1]:52191 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hG3yx-0000dT-Eo for importer@patchew.org; Mon, 15 Apr 2019 11:57:19 -0400 Received: from eggs.gnu.org ([209.51.188.92]:47647) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hG3x1-0007bi-4l for qemu-devel@nongnu.org; Mon, 15 Apr 2019 11:55:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hG3wz-0003Qf-5p for qemu-devel@nongnu.org; Mon, 15 Apr 2019 11:55:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46898) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hG3wt-0003Ch-EJ; Mon, 15 Apr 2019 11:55:11 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 152163002713; Mon, 15 Apr 2019 15:55:10 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-117-113.ams2.redhat.com [10.36.117.113]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8401060123; Mon, 15 Apr 2019 15:55:06 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 15 Apr 2019 17:54:49 +0200 Message-Id: <20190415155452.5115-2-kwolf@redhat.com> In-Reply-To: <20190415155452.5115-1-kwolf@redhat.com> References: <20190415155452.5115-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Mon, 15 Apr 2019 15:55:10 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 1/4] qcow2: Avoid COW during metadata preallocation X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" Limiting the allocation to INT_MAX bytes isn't particularly clever because it means that the final cluster will be a partial cluster which will be completed through a COW operation. This results in unnecessary data read and write requests which lead to an unwanted non-sparse filesystem block for metadata preallocation. Align the maximum allocation size down to the cluster size to avoid this situation. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake --- block/qcow2.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/qcow2.c b/block/qcow2.c index d507ee0686..c8400e9712 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2723,6 +2723,7 @@ static int qcow2_set_up_encryption(BlockDriverState *= bs, static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offs= et, uint64_t new_length) { + BDRVQcow2State *s =3D bs->opaque; uint64_t bytes; uint64_t host_offset =3D 0; unsigned int cur_bytes; @@ -2733,7 +2734,7 @@ static int coroutine_fn preallocate_co(BlockDriverSta= te *bs, uint64_t offset, bytes =3D new_length - offset; =20 while (bytes) { - cur_bytes =3D MIN(bytes, INT_MAX); + cur_bytes =3D MIN(bytes, QEMU_ALIGN_DOWN(INT_MAX, s->cluster_size)= ); ret =3D qcow2_alloc_cluster_offset(bs, offset, &cur_bytes, &host_offset, &meta); if (ret < 0) { --=20 2.20.1