Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
Message-ID: <e5664354-c07a-8313-5604-e7d1800ab1ef@oracle.com>
Date:   Wed, 4 Oct 2023 15:19:54 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.15.1
Subject: Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx
To:     "Darrick J. Wong" <djwong@kernel.org>
Cc:     Dave Chinner <david@fromorbit.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Eric Biggers <ebiggers@kernel.org>, axboe@kernel.dk,
        kbusch@kernel.org, hch@lst.de, sagi@grimberg.me,
        jejb@linux.ibm.com, martin.petersen@oracle.com,
        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,
        Prasad Singamsetty <prasad.singamsetty@oracle.com>
References: <20230929102726.2985188-1-john.g.garry@oracle.com>
 <20230929102726.2985188-4-john.g.garry@oracle.com>
 <20230929224922.GB11839@google.com>
 <b9c266d2-d5d6-4294-9a95-764641e295b4@acm.org>
 <d3a8b9b0-b24c-a002-e77d-56380ee785a5@oracle.com>
 <ZRtztUQvaWV8FgXW@dread.disaster.area>
 <20231003025703.GD21298@frogsfrogsfrogs>
 <da12e81d-cf29-6dd3-b01e-2319aa9487d5@oracle.com>
 <20231003154643.GF21298@frogsfrogsfrogs>
Content-Language: en-US
From:   John Garry <john.g.garry@oracle.com>
Organization: Oracle Corporation
In-Reply-To: <20231003154643.GF21298@frogsfrogsfrogs>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?MGFzVTE2Uk1JS3U3UG9TWVBHcy9mTlcvSEt0cDczNjhMSnUzWmRmdktUaUxP?=
 =?utf-8?B?TE1XTFdyN05zcDA5OFZGblJtM2RsT2xBS0s3NFovY2wxSllMVnVUVjErY2M0?=
 =?utf-8?B?ZUJiL3pocUdibTRGUVNKdCtaSXdNanBrKzh4YTF5b2ZrMDBCWmNSOFZQMlE2?=
 =?utf-8?B?cnV0VFdXZUtiZXkxYlcvZEU1M1VkWFNXclBWQkhObDJSRDZxUDVLaWVyQWRP?=
 =?utf-8?B?aUVpTXJ6MnpPckoyM1AxUGlzank3cDYyQmQxczFwbTdQU1Y3SzhiN0lWd3lq?=
 =?utf-8?B?TitITWROWUt0MkNuLy9NU3llR3ZFRGJCLzMzSE8zSDRPaktyN1VtdXRqMFNY?=
 =?utf-8?B?VnNDVHNzZmNTcXBnMm5rVkhhTU1ldm1Sc29UdTAwaEFqQU00VFlpSFVqZ2hN?=
 =?utf-8?B?MmJzd2ZPN1dpem0yQXdsL2l4ZGM2N2xIQXE0UjdUSlRGbkhpUUd3U1B0bGJU?=
 =?utf-8?B?NWlQenNUa0drR0NObHlBRVROVG50emZyTThyYm5xbXRKZ2Qwa2Z4cHJUTkVl?=
 =?utf-8?B?dE0zVTZmY0NSOWJMZlAzU3c4ZW42ZG94K24xSzFxNXZUVkRzRE82RHVDZCs4?=
 =?utf-8?B?R1JpSEtxRDFrNWpyQWhhamRQTkVWS2xOcnJRSXdKL0wzdXF5eDIrdEdwdW96?=
 =?utf-8?B?N3VhN29tNmFEbElRczJtQ1Z3dUZ3L1gxUjdRUzRJZEpBSklDcEJQbUVoWXg2?=
 =?utf-8?B?aFNvS2poaGdpdTM3VkJOM09ZTTVxOFBmaGI0TXZ1bEU1bUc3VGZHNjRYQThl?=
 =?utf-8?B?dVd6V1V4azNvNENHaGs5N3NaSlNkZjJlbmZRRnFwRHhIQ3Jzb0JMOGVYdmNs?=
 =?utf-8?B?S0toZHMyaWxiRTAzSjZCNElxYjJLRXBoNnJ2bUh6OEREb3IzVm9YMTdWZUJj?=
 =?utf-8?B?bUU1Y0c2b0RmQlJhbFFqQ2RLSkZacjlWcVFQaEFDWTB0UzJYRm5nR1NqcmI2?=
 =?utf-8?B?SUtTai9YbUJSQzNTMjZMZDBFdW1odGdWNXhKa3lWVVJXaTFaYTJtU0pEMXI5?=
 =?utf-8?B?ditzRVpPRXlVeUhmVzh2Y0VFbVpnbUhIaXpZWkxQTjdUUTA4Q2Z3SEVQV2dI?=
 =?utf-8?B?aGVRcmxBVkw2UXNRM1pQbUNwbHBzUEZJakl6Mng4THh0WWRqUGkzS3RtV09s?=
 =?utf-8?B?eHo0Qk1hOER0REdDakNkb0hDK2pOSnE2VE5jZnpWMFZvUE9wbW9Xb0JiUXlr?=
 =?utf-8?B?Y1BHMFdQVHNtYTZXc0FVcnJQTXBkSEoxVkVVSUtjbnZ0TVAzbjVwcC8zbEY1?=
 =?utf-8?B?RTdMd1ZpYkxkMjU5eWkyd2szUU5FaEZWUklNb1cxdE1VSG9lRVdRbG0rTWRh?=
 =?utf-8?B?bzJSdFNRZytZTVF5QmtLOWVMMFVkUFlZRFVUUUdCVVZjOHlVTzMzbFZaemo5?=
 =?utf-8?B?Zko5bjE4R0RnakduMnJNWUpYcUVoWHlSY3MxT0Y2NUJDZkJyb1djL2xFVXR5?=
 =?utf-8?B?OGNzQXZHWHJmVVAxZFgxWHlRZEY4UWt3R00vdU5OMGtWemN0dkNsaFQ3bDF1?=
 =?utf-8?B?cUMvUDFzQnZpQ1JmeEZ4WmpDNjRUdlRqVTdXRzA3eDBSYWJ5eFFuSE96MmlG?=
 =?utf-8?B?TkJrS0o0cHRLMC9MYTJUWU1yaHEzMUxIOE9LZW5oT3RjR2NJeHJIVUZlR3Qr?=
 =?utf-8?B?N2hWZndDSXpmSDEwc2pBd3dNeVVBUmV0NHdpMGVxV1lFdWVQRGJFRVFHbGdw?=
 =?utf-8?B?ZXd2TDVlZE9FVGNhWEwreXNlSHBjeDFPZEg4MkwzMFhhMW10YVpOOWdES3d2?=
 =?utf-8?B?ekt6V043MlltVnBQSWhjZ09jRTc5UzJOdWlTQ3ZtWVJvbTV1Qm9JeThQUkJj?=
 =?utf-8?B?R3puTmdINmlHRjFzcnhrQ0tWTlZiZmQyck5icC9qdHRXRWN3K1l0ZVBhN2k3?=
 =?utf-8?B?ZWJPVlZXUkxvR0VLZzJ4N3paZ1VNeXVxZ280V3NGbmg3VE43NktmSWQ1NFpL?=
 =?utf-8?B?VHZtTy9JUzZXak1hbjFKekt2STZBTG1LRk85N1YvNDIwTnhjM2pwdHNMTlVW?=
 =?utf-8?B?SVBRUTF1cEw5MEk4UFplejM1ZVQzbUxvWmdFejU0RjZLbno0VXVOOFp5VnVQ?=
 =?utf-8?B?STkvelhvYVBXWlpuc1JlaEYxa0EvSlVxeUJnTjZPSENxZUsxVVA3TXdJVE1r?=
 =?utf-8?Q?xkR6xtZmtaqZtrvTA1mBDwSL8?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?Q3M5YVVHQmo4RU5tanNlMHIxNDRtTDBZU0twOVl0YVR4clc1WS9NSHltYm9W?=
 =?utf-8?B?OEpsdVlmWXhWdFRqczM3YTNBTTlZTkFMMnNBZ25mQVpuKzJoTFJ1TGozcGQ5?=
 =?utf-8?B?ZkZNLzhMRnpDY3FhZmRMTXpYalkyVk1QQVR5WDVoL0I4SmpXenlJSUQxRVdt?=
 =?utf-8?B?c2hVaTlrbU1HNVMvNlB4eHdiNHpVTHM4YVBQL09JQm9TT2ptcDdWeDVqSmR5?=
 =?utf-8?B?WmxkdDJIMUNYSTQ1WlZpeWg3M3dXQ3BnRnYxMTQxdUVBbDhlRkVUTkp3NThy?=
 =?utf-8?B?dUpHQlhlSmtqbyszSzZ3dEFWa3VQZnArZlRIK2JadzM2eGxsWGZJdWR3NHZW?=
 =?utf-8?B?QWZ5M2E2a3ZWMTlPQysxcUR6N0x5TWNvVGhOZFQvVnlvdFRPdXc4TVh2NXRh?=
 =?utf-8?B?VFlJcm13bmxNNWlJa1VZR2dYcWpnOVJKS08xS01IZURZVVRmaFdaQmZjVmFm?=
 =?utf-8?B?bWxaVG9UUnpqQXMxcWJ1akFERHBOU3J0aWNBZWs1WU9JVmp1c04xM3FUMTYv?=
 =?utf-8?B?ZlRtWm4rZVV2ODcwcUcwRXJzNlV1djNBbm12YThXYVduaDJuemkyOVlteEY3?=
 =?utf-8?B?VDdvbGZrUUpCdW56Tmp5WEw5YUZ0Qm94SnRpV3F4bjNJeXNsOVVYc2MybmJp?=
 =?utf-8?B?YU5GNnhUMjBWWmkvNDFiR1JqT0Z1YnBSbFh1S0o2SFB4OHVXSTkyQ1haWUZs?=
 =?utf-8?B?RzhpOVpSTEQ2NEVGbFlMTDhuSDNubUYxcS83VGpGSUViZTBvQ3RMbTN4MmxI?=
 =?utf-8?B?aHpsamNDTFY4ZmdmTU96YzhlUXBObEFaZjFTdW5xSHd1RkVPdk1BdFRjYTh1?=
 =?utf-8?B?aVdNQmZUNlg3TWY1SFdwb1JlUmgyeTQrYWJNaThOd29BUUZHa3VuSWR4TlJP?=
 =?utf-8?B?amp1anVNT1RsZnRTWkF3S3IwK0prbmRDOEtycnI4Q0UvVk9scFlxSU1hUHVv?=
 =?utf-8?B?cHVldUl4NjNxdXQ0U05VMndoenp1d3NMb09pam1kcFVCVW1ML3BaaEM1bk9q?=
 =?utf-8?B?VGErLzMrZzNVMjAwRDZIdzFhNktacTV6Y0h6TmdRSEVISjN3dWJYbUFpajZB?=
 =?utf-8?B?RHNodmowSXMvYis0OEM1Y1kxYktDOXZjNG9IRGxOdHYrSEhPWlFEWEEvMG9Q?=
 =?utf-8?B?TERsSDV4V0k2MzE2U3JYaUZwSkppZDI1aVJXSzhta1hUS2pEbTVENitYdTFK?=
 =?utf-8?B?RmhZTzdOdmhlM2M3WGkyZXpjZ28zcnEvYmFpVElVQmFKVHpxYUNJS3RCWVVK?=
 =?utf-8?B?L2xJcjlqVWtsZC9QOVNsK3JTUExNVE9kNEJIVk82UUJmb3BwRHlUWW9CdTB3?=
 =?utf-8?B?RWtuckRVd1NnQ2owZVJ6L1NHQjdzSHZrVDFNZ2dnZUxqL1QyVzJ6dUpPTmNa?=
 =?utf-8?B?am5aeU1QQWpQR3QycGVaTUhNRFZJaEhaYmxrM0M2UGpxN242L0gzTzlHK1JT?=
 =?utf-8?B?TnFGZlBSdVgyYWNYQm83YjkyeHJBY044MXB5ZVlYKys3cTdHZ3BjU1FOb1VB?=
 =?utf-8?B?VHluM0N5Zk93TjJJTTYvRXRZSG9CdkJ0OHJZYXFQZXZ3eHFIdlJibXhZeWla?=
 =?utf-8?B?YWdydz09?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a8746f10-c3f6-4b84-d331-08dbc4e4fe94
X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB4313.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Oct 2023 14:20:00.8673
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: C0hozBqS5+YBPlUHvfU+tjXkzhX2R555aidJxsrYZLKqBAM1ZlgzS4RHoY4mKLY0XqdXvUqTrd+10unm2EZtyw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB5646
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_06,2023-10-02_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 spamscore=0
 phishscore=0 bulkscore=0 mlxlogscore=999 suspectscore=0 adultscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000
 definitions=main-2310040104
X-Proofpoint-GUID: DAB_0ak_jFWZ-gCwe_0J4cS93ypPVdMF
X-Proofpoint-ORIG-GUID: DAB_0ak_jFWZ-gCwe_0J4cS93ypPVdMF
X-Spam-Status: No, score=-2.4 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=unavailable
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Wed, 04 Oct 2023 07:20:54 -0700 (PDT)

On 03/10/2023 16:46, Darrick J. Wong wrote:
>>      stat->result_mask |= STATX_WRITE_ATOMIC;
> The result_mask (which becomes the statx stx_mask) needs to have
> STATX_WRITE_ATOMIC set any time a filesystem responds to
> STATX_WRITE_ATOMIC being set in the request_mask, even if the response
> is "not supported".
> 
> The attributes_mask also needs to have STATX_ATTR_WRITE_ATOMIC set if
> the filesystem+file can support the flag, even if it's not currently set
> for that file.  This should get turned into a generic vfs helper for the
> next fs that wants to support atomic write units:
> 
> static void generic_fill_statx_atomic_writes(struct kstat *stat,
> 		struct block_device *bdev)
> {
> 	u64 min_bytes;
> 
> 	/* Confirm that the fs driver knows about this statx request */
> 	stat->result_mask |= STATX_WRITE_ATOMIC;
> 
> 	/* Confirm that the file attribute is known to the fs. */
> 	stat->attributes_mask |= STATX_ATTR_WRITE_ATOMIC;
> 
> 	/* Fill out the rest of the atomic write fields if supported */
> 	min_bytes = queue_atomic_write_unit_min_bytes(bdev->bd_queue);
> 	if (min_bytes == 0)
> 		return;
> 
> 	stat->atomic_write_unit_min = min_bytes;
> 	stat->atomic_write_unit_max =
> 			queue_atomic_write_unit_max_bytes(bdev->bd_queue);
> 
> 	/* Atomic writes actually supported on this file. */
> 	stat->attributes |= STATX_ATTR_WRITE_ATOMIC;
> }
> 
> and then:
> 
> 	if (request_mask & STATX_WRITE_ATOMIC)
> 		generic_fill_statx_atomic_writes(stat, bdev);
> 
> 

That looks sensible, but, if used by an FS, we would still need a method 
to include extra FS restrictions, like extent alignment as in 15/21.

Thanks,
John