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Thu, 30 Apr 2020 09:30:24 -0400 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-409-d3aqS4zIPhmTGXrPaF1nFQ-1; Thu, 30 Apr 2020 09:30:21 -0400 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 A4957468; Thu, 30 Apr 2020 13:30:20 +0000 (UTC) Received: from linux.fritz.box.com (ovpn-114-60.ams2.redhat.com [10.36.114.60]) by smtp.corp.redhat.com (Postfix) with ESMTP id A5B2066071; Thu, 30 Apr 2020 13:30:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588253423; 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=vue8Ts5/jzDw8/CNpBo4HRBirBxWPkwn09a8hhQq3q8=; b=aioEDcSWPPvtOHmGDtiBaZNOvyuPPjmbw+jglgIQj8ST3Lh5OSe6awt4MXSDr56SjsQ4sj MAd5OZbjVOy9WLHA+rpeogPuNoTm4uSt2a/GuLS1EpHqb5+Y4lV3y1Z6LhUbBe3/+VcmD/ SrV8+Q8nA27A5ZNRgJBNj1zv7DVhbcI= X-MC-Unique: d3aqS4zIPhmTGXrPaF1nFQ-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PATCH 3/6] vmdk: Fix partial overwrite of zero cluster Date: Thu, 30 Apr 2020 15:30:04 +0200 Message-Id: <20200430133007.170335-4-kwolf@redhat.com> In-Reply-To: <20200430133007.170335-1-kwolf@redhat.com> References: <20200430133007.170335-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=207.211.31.81; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/30 01:31:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" When overwriting a zero cluster, we must not perform copy-on-write from the backing file, but from a zeroed buffer. Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake --- block/vmdk.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/block/vmdk.c b/block/vmdk.c index bdd7d2dcf1..da25b8992e 100644 --- a/block/vmdk.c +++ b/block/vmdk.c @@ -1340,7 +1340,9 @@ static void vmdk_refresh_limits(BlockDriverState *bs,= Error **errp) * get_whole_cluster * * Copy backing file's cluster that covers @sector_num, otherwise write ze= ro, - * to the cluster at @cluster_sector_num. + * to the cluster at @cluster_sector_num. If @zeroed is true, we're overwr= iting + * a zeroed cluster in the current layer and must not copy data from the + * backing file. * * If @skip_start_sector < @skip_end_sector, the relative range * [@skip_start_sector, @skip_end_sector) is not copied or written, and le= ave @@ -1351,18 +1353,21 @@ static int get_whole_cluster(BlockDriverState *bs, uint64_t cluster_offset, uint64_t offset, uint64_t skip_start_bytes, - uint64_t skip_end_bytes) + uint64_t skip_end_bytes, + bool zeroed) { int ret =3D VMDK_OK; int64_t cluster_bytes; uint8_t *whole_grain; + bool copy_from_backing; =20 /* For COW, align request sector_num to cluster start */ cluster_bytes =3D extent->cluster_sectors << BDRV_SECTOR_BITS; offset =3D QEMU_ALIGN_DOWN(offset, cluster_bytes); whole_grain =3D qemu_blockalign(bs, cluster_bytes); + copy_from_backing =3D bs->backing && !zeroed; =20 - if (!bs->backing) { + if (!copy_from_backing) { memset(whole_grain, 0, skip_start_bytes); memset(whole_grain + skip_end_bytes, 0, cluster_bytes - skip_end_b= ytes); } @@ -1377,7 +1382,7 @@ static int get_whole_cluster(BlockDriverState *bs, =20 /* Read backing data before skip range */ if (skip_start_bytes > 0) { - if (bs->backing) { + if (copy_from_backing) { /* qcow2 emits this on bs->file instead of bs->backing */ BLKDBG_EVENT(extent->file, BLKDBG_COW_READ); ret =3D bdrv_pread(bs->backing, offset, whole_grain, @@ -1397,7 +1402,7 @@ static int get_whole_cluster(BlockDriverState *bs, } /* Read backing data after skip range */ if (skip_end_bytes < cluster_bytes) { - if (bs->backing) { + if (copy_from_backing) { /* qcow2 emits this on bs->file instead of bs->backing */ BLKDBG_EVENT(extent->file, BLKDBG_COW_READ); ret =3D bdrv_pread(bs->backing, offset + skip_end_bytes, @@ -1631,7 +1636,8 @@ static int get_cluster_offset(BlockDriverState *bs, * or inappropriate VM shutdown. */ ret =3D get_whole_cluster(bs, extent, cluster_sector * BDRV_SECTOR= _SIZE, - offset, skip_start_bytes, skip_end_bytes); + offset, skip_start_bytes, skip_end_bytes, + zeroed); if (ret) { return ret; } --=20 2.25.3