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kbusch@kernel.org, sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.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, Alan Adamson References: <20230929102726.2985188-1-john.g.garry@oracle.com> <20230929102726.2985188-22-john.g.garry@oracle.com> <20231109153603.GA2188@lst.de> <20231109154619.GA3491@lst.de> Content-Language: en-US From: John Garry Organization: Oracle Corporation In-Reply-To: <20231109154619.GA3491@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: LO2P265CA0222.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:b::18) To DM6PR10MB4313.namprd10.prod.outlook.com (2603:10b6:5:212::20) Precedence: bulk X-Mailing-List: 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T+/TQiZpBtwZWs8seapxlYDvFt8REb0ViKa18+hOxY0LOe5IJZnEe5XC6rRphdb3CLOLha8swILHS8M933l4NQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR10MB7222 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-09_14,2023-11-09_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 malwarescore=0 suspectscore=0 adultscore=0 bulkscore=0 mlxlogscore=999 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311090138 X-Proofpoint-GUID: Du6umTe3sbVUQQ43zgYGKI-3_BMVcZBr X-Proofpoint-ORIG-GUID: Du6umTe3sbVUQQ43zgYGKI-3_BMVcZBr On 09/11/2023 15:46, Christoph Hellwig wrote: > On Thu, Nov 09, 2023 at 03:42:40PM +0000, Matthew Wilcox wrote: >> That wasn't the model we had in mind. In our thinking, it was fine to >> send a write that crossed the atomic write limit, but the drive wouldn't >> guarantee that it was atomic except at the atomic write boundary. >> Eg with an AWUN of 16kB, you could send five 16kB writes, combine them >> into a single 80kB write, and if the power failed midway through, the >> drive would guarantee that it had written 0, 16kB, 32kB, 48kB, 64kB or >> all 80kB. Not necessarily in order; it might have written bytes 16-32kB, >> 64-80kB and not the other three. I didn't think that there are any atomic write guarantees at all if we ever exceed AWUN or AWUPF or cross the atomic write boundary (if any). > I can see some use for that, but I'm really worried that debugging > problems in the I/O merging and splitting will be absolute hell. Even if bios were merged for NVMe the total request length still should not exceed AWUPF. However a check can be added to ensure this for a submitted atomic write request. As for splitting, it is not permitted for atomic writes and only a single bio is permitted to be created per write. Are more integrity checks required? Thanks, John