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Petersen" , John Garry , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, jejb@linux.ibm.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, chandan.babu@oracle.com, dchinner@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-api@vger.kernel.org, Himanshu Madhani Subject: Re: [PATCH 01/21] block: Add atomic write operations to request_queue limits From: "Martin K. Petersen" Organization: Oracle Corporation Message-ID: References: <20230929102726.2985188-1-john.g.garry@oracle.com> <20230929102726.2985188-2-john.g.garry@oracle.com> <7f031c7a-1830-4331-86f9-4d5fbca94b8a@acm.org> <776ff7e4-879f-4967-ba46-fd170804a9e0@acm.org> Date: Wed, 04 Oct 2023 14:26:42 -0400 In-Reply-To: <776ff7e4-879f-4967-ba46-fd170804a9e0@acm.org> (Bart Van Assche's message of "Wed, 4 Oct 2023 10:28:10 -0700") Content-Type: text/plain X-ClientProxiedBy: PH8PR21CA0023.namprd21.prod.outlook.com (2603:10b6:510:2ce::20) To PH0PR10MB4759.namprd10.prod.outlook.com (2603:10b6:510:3d::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR10MB4759:EE_|CY8PR10MB6537:EE_ X-MS-Office365-Filtering-Correlation-Id: cdf8bea6-bb50-4e29-cba8-08dbc50776de X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-04_10,2023-10-02_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 malwarescore=0 adultscore=0 suspectscore=0 mlxlogscore=785 bulkscore=0 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310040134 X-Proofpoint-GUID: HGRCpqJOJj2PMk0M3WMS0k-z6g0o2uYs X-Proofpoint-ORIG-GUID: HGRCpqJOJj2PMk0M3WMS0k-z6g0o2uYs Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bart, > In my opinion there is a contradiction between the above reply and > patch 19/21 of this series. Data written with the SCSI WRITE ATOMIC > command is not guaranteed to survive a power failure. That is not the intent. The intent is to ensure that for any given application block (say 16KB), the application block on media will contain either 100% old data or 100% new data. Always. If a storage device offers no such guarantee across a power failure, then it is not suitable for use by applications which do not tolerate torn writes. That is why the writes-are-atomic-unless-there's-a-problem variant of the values reports in NVMe are of no interest. -- Martin K. Petersen Oracle Linux Engineering