From nobody Sun Feb 8 20:12:43 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 ARC-Seal: i=1; a=rsa-sha256; t=1563901585; cv=none; d=zoho.com; s=zohoarc; b=hV8LQA67hPcHQGKBxh0pezlbm5t8VcuHJxNXCDCRjqwrO6CEJnSnnSVhA7d7dvPxkSESoPuR0+kZUhYyi7YhDk8qIFd6o8H0RYFpo4Z9JeQRXSbXwnMbxTCB/3ENZeG7+nAU55K+xVYwiwhKx6p+20S3tQsB5OqQnGLh5GAT8DI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1563901585; h=Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=YQWBtaW8y/Zcisjve24P6gde9G32IxO3EV9QK4la5ks=; b=HblNxElvl+MKKrKeT1T3DMqWFipKCGqCqj2TLpL5pHlH/S8LkBUlynf2n04xK3yygSAHtW94P5At4duo6UhRCIKs6qiqO7DnP2wkXwUK1YyIY8kVKJK6+XpeY4RHW9ZV+fhOcpOzdJOqCPjJilYtJRqnQqaRrcnRpyucyMtoyVE= 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 Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1563901585516163.79064532729524; Tue, 23 Jul 2019 10:06:25 -0700 (PDT) Received: from localhost ([::1]:45914 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hpyF6-0003q8-1R for importer@patchew.org; Tue, 23 Jul 2019 13:06:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43217) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hpyBE-0007TZ-AS for qemu-devel@nongnu.org; Tue, 23 Jul 2019 13:02:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hpyBC-00062R-5s for qemu-devel@nongnu.org; Tue, 23 Jul 2019 13:02:24 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:16318 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hpyBA-0005ob-4C for qemu-devel@nongnu.org; Tue, 23 Jul 2019 13:02:20 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6NH25VM048740 for ; Tue, 23 Jul 2019 13:02:08 -0400 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tx61fghbd-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 23 Jul 2019 13:02:06 -0400 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 23 Jul 2019 18:01:27 +0100 Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6NH1QuV60555624 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 23 Jul 2019 17:01:26 GMT Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0DCECBE062; Tue, 23 Jul 2019 17:01:26 +0000 (GMT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E8D50BE058; Tue, 23 Jul 2019 17:01:25 +0000 (GMT) Received: from localhost (unknown [9.53.179.212]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 23 Jul 2019 17:01:25 +0000 (GMT) From: Michael Roth To: qemu-devel@nongnu.org Date: Tue, 23 Jul 2019 12:01:02 -0500 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190723170104.4327-1-mdroth@linux.vnet.ibm.com> References: <20190723170104.4327-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19072317-0004-0000-0000-0000152DB9B3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011482; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000287; SDB=6.01236375; UDB=6.00651638; IPR=6.01017731; MB=3.00027856; MTD=3.00000008; XFM=3.00000015; UTC=2019-07-23 17:01:29 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19072317-0005-0000-0000-00008C9463C7 Message-Id: <20190723170104.4327-35-mdroth@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-07-23_07:, , 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=8.0.1-1906280000 definitions=main-1907230170 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PATCH 34/36] block/file-posix: Unaligned O_DIRECT block-status 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, Max Reitz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Max Reitz Currently, qemu crashes whenever someone queries the block status of an unaligned image tail of an O_DIRECT image: $ echo > foo $ qemu-img map --image-opts driver=3Dfile,filename=3Dfoo,cache.direct=3Don Offset Length Mapped to File qemu-img: block/io.c:2093: bdrv_co_block_status: Assertion `*pnum && QEMU_IS_ALIGNED(*pnum, align) && align > offset - aligned_offset' failed. This is because bdrv_co_block_status() checks that the result returned by the driver's implementation is aligned to the request_alignment, but file-posix can fail to do so, which is actually mentioned in a comment there: "[...] possibly including a partial sector at EOF". Fix this by rounding up those partial sectors. There are two possible alternative fixes: (1) We could refuse to open unaligned image files with O_DIRECT altogether. That sounds reasonable until you realize that qcow2 does necessarily not fill up its metadata clusters, and that nobody runs qemu-img create with O_DIRECT. Therefore, unpreallocated qcow2 files usually have an unaligned image tail. (2) bdrv_co_block_status() could ignore unaligned tails. It actually throws away everything past the EOF already, so that sounds reasonable. Unfortunately, the block layer knows file lengths only with a granularity of BDRV_SECTOR_SIZE, so bdrv_co_block_status() usually would have to guess whether its file length information is inexact or whether the driver is broken. Fixing what raw_co_block_status() returns is the safest thing to do. There seems to be no other block driver that sets request_alignment and does not make sure that it always returns aligned values. Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf (cherry picked from commit 9c3db310ff0b7473272ae8dce5e04e2f8a825390) Signed-off-by: Michael Roth --- block/file-posix.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/block/file-posix.c b/block/file-posix.c index 07bbdab953..df467f510b 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2461,6 +2461,8 @@ static int coroutine_fn raw_co_block_status(BlockDriv= erState *bs, off_t data =3D 0, hole =3D 0; int ret; =20 + assert(QEMU_IS_ALIGNED(offset | bytes, bs->bl.request_alignment)); + ret =3D fd_open(bs); if (ret < 0) { return ret; @@ -2486,6 +2488,20 @@ static int coroutine_fn raw_co_block_status(BlockDri= verState *bs, /* On a data extent, compute bytes to the end of the extent, * possibly including a partial sector at EOF. */ *pnum =3D MIN(bytes, hole - offset); + + /* + * We are not allowed to return partial sectors, though, so + * round up if necessary. + */ + if (!QEMU_IS_ALIGNED(*pnum, bs->bl.request_alignment)) { + int64_t file_length =3D raw_getlength(bs); + if (file_length > 0) { + /* Ignore errors, this is just a safeguard */ + assert(hole =3D=3D file_length); + } + *pnum =3D ROUND_UP(*pnum, bs->bl.request_alignment); + } + ret =3D BDRV_BLOCK_DATA; } else { /* On a hole, compute bytes to the beginning of the next extent. = */ --=20 2.17.1