From patchwork Thu Dec 5 13:46:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ritesh Harjani X-Patchwork-Id: 11274767 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 E9E57112B for ; Thu, 5 Dec 2019 13:46:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFF272464D for ; Thu, 5 Dec 2019 13:46:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729456AbfLENqT (ORCPT ); Thu, 5 Dec 2019 08:46:19 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:62198 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729165AbfLENqT (ORCPT ); Thu, 5 Dec 2019 08:46:19 -0500 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xB5Dh3qW063629 for ; Thu, 5 Dec 2019 08:46:18 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2wq1ky4e9a-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 05 Dec 2019 08:46:17 -0500 Received: from localhost by e06smtp07.uk.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) Thu, 5 Dec 2019 13:46:13 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xB5DkCoR49020952 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 5 Dec 2019 13:46:12 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5022AA405C; Thu, 5 Dec 2019 13:46:12 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ADAE2A4062; Thu, 5 Dec 2019 13:46:10 +0000 (GMT) Received: from dhcp-9-199-159-163.in.ibm.com (unknown [9.199.159.163]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 5 Dec 2019 13:46:10 +0000 (GMT) From: Ritesh Harjani To: jack@suse.cz, tytso@mit.edu, linux-ext4@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, mbobrowski@mbobrowski.org, riteshh@linux.ibm.com, joseph.qi@linux.alibaba.com Subject: [PATCHv4 3/3] ext4: Move to shared i_rwsem even without dioread_nolock mount opt Date: Thu, 5 Dec 2019 19:16:05 +0530 X-Mailer: git-send-email 2.21.0 In-Reply-To: <20191205120529.GB32639@quack2.suse.cz> References: <20191205120529.GB32639@quack2.suse.cz> MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 19120513-0028-0000-0000-000003C55B99 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19120513-0029-0000-0000-000024887DB2 Message-Id: <20191205134605.2593-1-riteshh@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-05_03:2019-12-04,2019-12-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 mlxlogscore=548 malwarescore=0 priorityscore=1501 impostorscore=0 mlxscore=0 bulkscore=0 phishscore=0 lowpriorityscore=0 suspectscore=3 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912050115 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org We were using shared locking only in case of dioread_nolock mount option in case of DIO overwrites. This mount condition is not needed anymore with current code, since:- 1. No race between buffered writes & DIO overwrites. Since buffIO writes takes exclusive lock & DIO overwrites will take shared locking. Also DIO path will make sure to flush and wait for any dirty page cache data. 2. No race between buffered reads & DIO overwrites, since there is no block allocation that is possible with DIO overwrites. So no stale data exposure should happen. Same is the case between DIO reads & DIO overwrites. 3. Also other paths like truncate is protected, since we wait there for any DIO in flight to be over. Reviewed-by: Jan Kara Signed-off-by: Ritesh Harjani --- fs/ext4/file.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index cbafaec9e4fc..682ed956eb02 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -392,8 +392,8 @@ static const struct iomap_dio_ops ext4_dio_write_ops = { * - For extending writes case we don't take the shared lock, since it requires * updating inode i_disksize and/or orphan handling with exclusive lock. * - * - shared locking will only be true mostly with overwrites in dioread_nolock - * mode. Otherwise we will switch to exclusive i_rwsem lock. + * - shared locking will only be true mostly with overwrites. Otherwise we will + * switch to exclusive i_rwsem lock. */ static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from, bool *ilock_shared, bool *extend) @@ -415,14 +415,11 @@ static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from, *extend = true; /* * Determine whether the IO operation will overwrite allocated - * and initialized blocks. If so, check to see whether it is - * possible to take the dioread_nolock path. - * + * and initialized blocks. * We need exclusive i_rwsem for changing security info * in file_modified(). */ if (*ilock_shared && (!IS_NOSEC(inode) || *extend || - !ext4_should_dioread_nolock(inode) || !ext4_overwrite_io(inode, offset, count))) { inode_unlock_shared(inode); *ilock_shared = false;