From patchwork Thu Oct 31 03:29:48 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 11220561 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DAA861515 for ; Thu, 31 Oct 2019 03:30:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3BC220873 for ; Thu, 31 Oct 2019 03:30:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="MGKb6w0a" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726552AbfJaDaE (ORCPT ); Wed, 30 Oct 2019 23:30:04 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:49450 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726336AbfJaDaE (ORCPT ); Wed, 30 Oct 2019 23:30:04 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x9V3TCaR024791; Thu, 31 Oct 2019 03:29:51 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : mime-version : content-type; s=corp-2019-08-05; bh=XDUxscILsJ13tPTDg3J62ds2i/L80cksUFSZ1N7K4OQ=; b=MGKb6w0an2ZK4Jt9N4Zo6+jDTSUaP3qxwplSI55jx0Vs49EEqIAmJWu9JHJPqCoWNquf jepFpe3XcpLjMZ0GoEyGOq3ZPB2DQjpkfYiaGBAfj0l9Fa9ESFf71gYOt7gI6BFudbjt /42BV7CEJiT4HBD1QpM74/fiXbvmbmwFBhXbzlexHnHc43hqZ316n1Z2ZhadsN0UIGxZ toV3elyEcegfSM2Q1eUZp55vuPCcQUVq3PGqKxF+uJ6GMeK9PdlmCnDRql3QU+SwKeed 9rJ7n/X9tnPxetRUpl08UlS2lseoP+psXwfjbeump163UyZ1Pv1xF6ar+bhfytNVX8ig IA== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2130.oracle.com with ESMTP id 2vxwhfr77n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 31 Oct 2019 03:29:50 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x9V3Nr20125950; Thu, 31 Oct 2019 03:29:50 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3030.oracle.com with ESMTP id 2vykw0h5km-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 31 Oct 2019 03:29:50 +0000 Received: from abhmp0022.oracle.com (abhmp0022.oracle.com [141.146.116.28]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x9V3TnFu021188; Thu, 31 Oct 2019 03:29:49 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 30 Oct 2019 20:29:49 -0700 Date: Wed, 30 Oct 2019 20:29:48 -0700 From: "Darrick J. Wong" To: Jens Axboe , Christoph Hellwig Cc: linux-block@vger.kernel.org, linux-fsdevel , xfs Subject: [PATCH v4] loop: fix no-unmap write-zeroes request behavior Message-ID: <20191031032948.GA15212@magnolia> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9426 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910310031 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9426 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 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-1910310032 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Darrick J. Wong Currently, if the loop device receives a WRITE_ZEROES request, it asks the underlying filesystem to punch out the range. This behavior is correct if unmapping is allowed. However, a NOUNMAP request means that the caller doesn't want us to free the storage backing the range, so punching out the range is incorrect behavior. To satisfy a NOUNMAP | WRITE_ZEROES request, loop should ask the underlying filesystem to FALLOC_FL_ZERO_RANGE, which is (according to the fallocate documentation) required to ensure that the entire range is backed by real storage, which suffices for our purposes. Fixes: 19372e2769179dd ("loop: implement REQ_OP_WRITE_ZEROES") Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- v4: add review tags v3: refactor into a single fallocate function v2: reorganize a little according to hch feedback --- drivers/block/loop.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index f6f77eaa7217..ef6e251857c8 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -417,18 +417,20 @@ static int lo_read_transfer(struct loop_device *lo, struct request *rq, return ret; } -static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos) +static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos, + int mode) { /* - * We use punch hole to reclaim the free space used by the - * image a.k.a. discard. However we do not support discard if - * encryption is enabled, because it may give an attacker - * useful information. + * We use fallocate to manipulate the space mappings used by the image + * a.k.a. discard/zerorange. However we do not support this if + * encryption is enabled, because it may give an attacker useful + * information. */ struct file *file = lo->lo_backing_file; - int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE; int ret; + mode |= FALLOC_FL_KEEP_SIZE; + if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) { ret = -EOPNOTSUPP; goto out; @@ -596,9 +598,17 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq) switch (req_op(rq)) { case REQ_OP_FLUSH: return lo_req_flush(lo, rq); - case REQ_OP_DISCARD: case REQ_OP_WRITE_ZEROES: - return lo_discard(lo, rq, pos); + /* + * If the caller doesn't want deallocation, call zeroout to + * write zeroes the range. Otherwise, punch them out. + */ + return lo_fallocate(lo, rq, pos, + (rq->cmd_flags & REQ_NOUNMAP) ? + FALLOC_FL_ZERO_RANGE : + FALLOC_FL_PUNCH_HOLE); + case REQ_OP_DISCARD: + return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE); case REQ_OP_WRITE: if (lo->transfer) return lo_write_transfer(lo, rq, pos);