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Tue, 01 Oct 2019 23:47:23 +0000 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x91NlMVY54133144 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 1 Oct 2019 23:47:22 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AE2142805A; Tue, 1 Oct 2019 23:47:22 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9293F28058; Tue, 1 Oct 2019 23:47:22 +0000 (GMT) Received: from localhost (unknown [9.53.179.213]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 1 Oct 2019 23:47:22 +0000 (GMT) From: Michael Roth To: qemu-devel@nongnu.org Subject: [PATCH 01/97] qcow2: Avoid COW during metadata preallocation Date: Tue, 1 Oct 2019 18:44:40 -0500 Message-Id: <20191001234616.7825-2-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191001234616.7825-1-mdroth@linux.vnet.ibm.com> References: <20191001234616.7825-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-10-01_10:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010203 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 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: Kevin Wolf , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Kevin Wolf 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 (cherry picked from commit f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4) Signed-off-by: Michael Roth --- block/qcow2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/qcow2.c b/block/qcow2.c index 3ace3b2209..dfac74c264 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2734,7 +2734,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset, bytes = new_length - offset; while (bytes) { - cur_bytes = MIN(bytes, INT_MAX); + cur_bytes = MIN(bytes, QEMU_ALIGN_DOWN(INT_MAX, s->cluster_size)); ret = qcow2_alloc_cluster_offset(bs, offset, &cur_bytes, &host_offset, &meta); if (ret < 0) { -- 2.17.1