From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="dFZ+dvmh"; dkim=pass (1024-bit key) header.d=oracle.onmicrosoft.com header.i=@oracle.onmicrosoft.com header.b="O7CoGlpS" Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84F59A7; Tue, 28 Nov 2023 00:57:09 -0800 (PST) Received: from pps.filterd (m0246627.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3AS8YBCb020856; Tue, 28 Nov 2023 08:56:46 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=message-id : date : subject : from : to : cc : references : in-reply-to : content-type : content-transfer-encoding : mime-version; s=corp-2023-11-20; bh=J3SV7koUqNwnstklPVEKbZdt7Jahxpt5hhW43yeCf8Q=; b=dFZ+dvmh/qvxoDtL8ZxkhCqagJpe9tEL83VAGi2WnMMVi2SghvRQFzlPNYoJAMAR5LZ5 Quzn6E7+lqzyvrm2qiFU6qGEtsLR7LFu9EblEC6ACqdT3yVX/8Fphde1Drkjgj6knQBv FQrMW+XvSOLqnDv9d30lQ3rZRgI1q33CTeFjcfzO/MQWwjIlOsIsY9uBLLqmicR7u6tr GaZgm9S7ob6WZqVyU8GkiQV5IYQT6QisQEMYeV30mtLWXG99cagDYbXZ0I0d6M1Qh+0H T0upgVIJn5u1MVNv0SzVUlvp8QY0OEWVjbzNsOOp6okvKd6Duccef6eqA7zSUf3tTFbJ Zw== Received: from iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta01.appoci.oracle.com [130.35.100.223]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3uk7h2n515-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 Nov 2023 08:56:45 +0000 Received: from pps.filterd (iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (8.17.1.19/8.17.1.19) with ESMTP id 3AS8TvxJ027045; Tue, 28 Nov 2023 08:56:44 GMT Received: from nam02-sn1-obe.outbound.protection.outlook.com (mail-sn1nam02lp2040.outbound.protection.outlook.com [104.47.57.40]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 3uk7cctbn6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 Nov 2023 08:56:44 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=EqnIgQKJ4n9k6hwmWDQzr4QGhfxXVZE5ymoNVVCRsT1ae5pJ7C1TFwtZeOBx5TEBqER+jaUBg8lgngvP0ubPC1oIdqIGN3HtS1Ak3h2IcG7zhaT0PZU5nsdD+IcMhMwg1Ze9ti5sTWg5bNr2ZAL1zmfd5XLtXFCxG1e6MaRqAtJSHLoawWoUNQXaYMZqfIUQwqHV0+TCG+fHdOngr6fiKFbagPLGADlrF8aZ50evvSqpRjr3MaLV1r4nn/EJ/oF5fn33gWxRZJL4A8/URof4vUFS54OSdS66B/hTAe7JrNzLcYn1z6TbkfwjKeO3Wn9GUkGA8PAM3ytBKA0VufDi3w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=J3SV7koUqNwnstklPVEKbZdt7Jahxpt5hhW43yeCf8Q=; b=D3hXCPNqRHObY5L0P0crTWIFqxJMe9bcr20h8KRkp9vKVwbikDCBYB3lkYUXNrSCWYN7QZIoNFiW1AZCs4B61q/SRqVpFdFchRIvBxfD6HHGuultKUSwb7JtFzITv/6A+UPJJ5IhzSm+O7zLDaTVBF/iCG1gUPf5BWSb6/vf0za5FJmuwsEoTLjxDWV9M8CzuVEcIcMao9VNykWJQpLoP+yommtEQ1NXC27qqd7HWVfcJYiElBBly7E7HLwMkgVXj0XtdTJO+ouu9tXQoZk4IOdYTllxBgOYEFVCutEh/RTOZqpNPoy2PKQnxW6hEd2GnwQKXQ0FMMoH7ST20gcmxw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=J3SV7koUqNwnstklPVEKbZdt7Jahxpt5hhW43yeCf8Q=; b=O7CoGlpSmB32AJp83ZKZDehWNCTQ5n9H4779Be6BlxtONKcX0UeUyrmvFevVui7txNX7ZqvH2At/gi4Pd1wLHYipgLQJ4Z8gnFeVUgBhPw5dWVQeTjwIsVmY3e7ds8VFWW5uCfzIHz3I41Oc4iWtOL5P4wy5tOGuQsDV4YzJbI8= Received: from DM6PR10MB4313.namprd10.prod.outlook.com (2603:10b6:5:212::20) by DS7PR10MB7376.namprd10.prod.outlook.com (2603:10b6:8:d9::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7025.27; Tue, 28 Nov 2023 08:56:42 +0000 Received: from DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::102a:f31:30c6:3187]) by DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::102a:f31:30c6:3187%4]) with mapi id 15.20.7025.022; Tue, 28 Nov 2023 08:56:42 +0000 Message-ID: Date: Tue, 28 Nov 2023 08:56:37 +0000 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 17/21] fs: xfs: iomap atomic write support From: John Garry To: Christoph Hellwig Cc: axboe@kernel.dk, 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 References: <20230929102726.2985188-1-john.g.garry@oracle.com> <20230929102726.2985188-18-john.g.garry@oracle.com> <20231109152615.GB1521@lst.de> Content-Language: en-US Organization: Oracle Corporation In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: LO4P123CA0462.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:1aa::17) To DM6PR10MB4313.namprd10.prod.outlook.com (2603:10b6:5:212::20) Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6PR10MB4313:EE_|DS7PR10MB7376:EE_ X-MS-Office365-Filtering-Correlation-Id: 3350faf5-023f-4092-d272-08dbefeff0ca 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-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM6PR10MB4313.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(376002)(346002)(39860400002)(396003)(366004)(136003)(230922051799003)(1800799012)(186009)(451199024)(64100799003)(38100700002)(41300700001)(36756003)(86362001)(31686004)(83380400001)(5660300002)(7416002)(26005)(2616005)(2906002)(31696002)(6512007)(36916002)(6506007)(6666004)(8676002)(4326008)(8936002)(478600001)(6486002)(66556008)(66946007)(66476007)(316002)(6916009)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?UjVsYzBkdERlRUZ6dmtmb1RtTWNJMUc4NlZVb1NDa2tvM2Nad1dOL2hhclps?= =?utf-8?B?S25HcnlnNDZ0WDB0bGVPVURtY3l3R3dYcEN1cVBMZkxxS0xiaDRBQm1Zdnpp?= =?utf-8?B?QmthYytDeGdJbklrSzd0bXJTT3ozZ1d2Rm5aTWtvOThMaFc0aHdLZlhtOVUw?= =?utf-8?B?alhkSVZFbUNtOTJTUVRRV0MvSWZza0liaXBvcEd2SFo2c2RVbWprVndrOVpO?= =?utf-8?B?OWRDeWRTYVIvbUpmU3g2ak1CR2lGUTM5Vm1nb3Q2MGZITXEweklzZlZhaFRm?= =?utf-8?B?RHJZdWI3VGtHdVJpK3hVOVNnVlU0TUV0cHVzRUxZaitlRGQ5QkMrdWU5VEZC?= =?utf-8?B?ZmlwN2c4R0t6dE10WE5vWHdrRnZEZlphdUgxZGVnQW9KVkM1OEJGRFVYbEtL?= =?utf-8?B?WjFXaHJDU1hKVjJmTklVQXhoajBjMXE0ckd0WHhsbGpqNWJxaUU2eTJJUGNs?= =?utf-8?B?UWdNbHBqQ3BFWENCOEhyQXhxS0lWTEFidTVKYUNqSy9qYzNsMlhsbzFtVElj?= =?utf-8?B?R3lKeU5jNWJrRDZlYUVza0NqS0hSandPWWl3aVV3YkpnUFRBdEJXaWJvaEJh?= =?utf-8?B?eEVsUXViMGEvTFpFd0hRcU1pSVZJQmxocmFlQVFHOHZNUW1PVGJ5ZHFKTzBj?= =?utf-8?B?ci9pTFA0eGU2aTIyVlpUa252S3YxME5MN3lpRGFIWkNicXlsaEluOXJkdDB3?= =?utf-8?B?QTJQUnMxZUNNYnM1V3p2ZGIvY2FzN3RodzFKUThOREd2RXJyMTlpUHhmd3Ft?= =?utf-8?B?RENhUkFvYlJkNlNnT0cyQXg2VVNWVkc5OFRiSDg1REV4NlkwMlkvRHFUK1Nj?= =?utf-8?B?TnZSeVd1UFF3R2dEVnQzdEJ6N3NXUStiYTEvU0NjbFJUU3hZWlFXQnpXR0du?= =?utf-8?B?eG5UMGFPYkExVkR6akpBZFJIQitWVjlTbkp2eXFyUEl6cEtrRk5wK041MWpV?= =?utf-8?B?bzdUOWZuVW0rSm5kbFhjdGF1cnBmWWtKTlBqSlNUNkYvd0hlNzBRYXBqNmJQ?= =?utf-8?B?MXdDYTJMb2FNK0R6QWE4UFdEQktEUW5iWlhsNVdDamFGRERyTGRXTTV0SHZY?= =?utf-8?B?VGJOaXM5TUtHY0dodGpwTFozemo4VVM0L0puT0haRWNWclRKRzVmeUN0ek82?= =?utf-8?B?elNaTWttQlc5OUY4WWtCeE1DUzhNT2xGQXJOWmN5MW1jUllSMWNJcGR3K2Rr?= =?utf-8?B?eUErWk1HSTRtaUdpRmU4WklSY29rM3VYcGIyQ2c4T256TWt1Z2x1L2dDSEdS?= =?utf-8?B?SjdWM1JzcllwUmJXUDZQY1BYMmhieGViaUVkUE9TaEJrL0VleFJkblhBNXZi?= =?utf-8?B?N0MvMzVvdHJ1RkFML1BmeEhYQThSUlZCSkowS251ZUY1bmhrWU80ZCtFbFk0?= =?utf-8?B?Uk0weXdvU0dKN04zdzFmRUpVeUV3WHcvTitNeHlic1UvYXgwTW4wekFVbWxr?= =?utf-8?B?cTZzZFlUZlRHRVNUWHN4VE12dUNnWUszS0lZcnBORDZLM21sQnk5cXYwcHNC?= =?utf-8?B?d25KVHBGN0NuZWYrU1hRRHFKZHRYN0U3RG5BS0xYYWlndkpPUVlKTWVHWXVW?= =?utf-8?B?UHhjb1RRYlFrcFpaV3B3SzlHalRHZkNOdW9NTHVqWWk4enpjZ0o5a2MxTFdi?= =?utf-8?B?RnZvYnBmQURmNlpmQnVWeDdia2NFalhkcklkY0RQcDkzcjErSmdDWDJIZXFU?= =?utf-8?B?YWhIakpFczhCRFI0V21WN3dML3ArdVczZ1ZZK20vVVl5em9WS3FiSnptc3hX?= =?utf-8?B?cDRKbFNmRGhveVlUK3BQb3UxU2lXb2x3OHV0dVhRWENrbVV5b21FdzdrL3lN?= =?utf-8?B?ZVFNc29xZUhQRmJXSVlkbHNHT2xSaWIzZjRzenM0WU1zUzFPZENFakw5SG13?= =?utf-8?B?bklDclhzVnZSWEQ0SzNSN0RvYWlqR3VrTnZ3NldKZWxZdGRWSkRaTjQwUHFE?= =?utf-8?B?QlJWUDF0aFEwcDRWV0RQZDRxL1Zab3dXZFh4OHl3Nm56cWM0dmFmZlZONWhR?= =?utf-8?B?WUE3NkJCYnRncXEyYjBHYWxJaVFWSmxLTzBjcmxscmRzTnh1S24yWFdWREFn?= =?utf-8?B?K0w5ZVNOUUxtdCt4bTcrVm0zUi9EU1RxQ1lmUHF1LzZ5RkZURnM2VWh3cUlt?= =?utf-8?Q?vIs2pH27IIXhvTq5AHcXe+vCN?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?RjhqbjZNd3lTSnFBUENOaHZhbjYzek02T2hPVCtlbVBxQ1ViZ2tMN2pvdUxK?= =?utf-8?B?OW9tT2szVnZ4NnduWGV1cDlkU3psaXFGNjhaUm1vL1VWUDdvbW9LcUxSTnRs?= =?utf-8?B?UTJQeUxiMmJxTXVVR1drRUt4TDRxbG9WWkJDNm5SOWpPV3RjM1BUK3ptUlFu?= =?utf-8?B?UUVLYmtyMThvdzlWRTcxdkpxL1VlRUxZZ3BGc285V3k2TnVQdDJ6cnl1MVli?= =?utf-8?B?eU1GdGtMMlJHdlN0K2FBUHJRWEFEY1NjN1IyMVdod1hPR2ZGWW9OZEEyU0lM?= =?utf-8?B?UkY2QkR5NnlOMkZ4cGZKL0h4WmRSRkdGWHoySVRqU01oblk4Y3hCUW94K0hO?= =?utf-8?B?MVVRRG1Yczl5U2o0QW44RkxXU25jbGxnR0NJbVc3YVJwQ1ZXV1VqVU9WMi9m?= =?utf-8?B?Rml1ckRsa0JHeC9GdHNMNEdhRDRGWHZwN1I5UkF2OTY3bmFVcVdSck05V25Z?= =?utf-8?B?c2NhY3pIVnBxYUtKV2NqUTdDSUJ5Y2xNWXVxQVBmOWhOMlZFVTJTeEwxK3NO?= =?utf-8?B?NnJ1U2JycTBrSTR6bWdpWEtEL3hoaFgrYTlxUW5kL05QQ1MraVNVVkcyVy96?= =?utf-8?B?bEsvT0FhVWo3TTdTdmN5cEdOVlpGQlc5dEhDZ09NeDYwdE9Fb1BzdXYvaUpS?= =?utf-8?B?K2JWN2JHTGk0cUdJbXNPcjBZMW1XNi9nQllick8wUlcyZVk1L2w4OG8ybTE5?= =?utf-8?B?WU44T3BmMGhXaXdsM0lDQVdpTS9GSFRBNkFSUGRlYnBQVEJTTjJQSmtTbVhB?= =?utf-8?B?Z1FsdllpVmZ4VllibGM3cVhvaUdpeE1ab3VxbVd5OHd2WEcxVk1aSzVqbnNa?= =?utf-8?B?MEtIT1p2SmoreXJsNHRuU3h3aERiUnlTc2xTaHNjQlkxMUtWTnVKY04zMDI3?= =?utf-8?B?dmZrMHROaEZKSXRIZUduUTcwRGtyWS9hWXBlN08vNmVKdzA5S3RqK2h0MDJq?= =?utf-8?B?d3dGMnVlcE4yZXJ5SGFuOE51SWVxNkxTMzA5RW01ajdIMEp4WEZoWk5QbkdV?= =?utf-8?B?VHNPQm5MWCs5WlFQazdyOHZSbHY3Sm9idzF3Zng3T2c2TDMvaWxzSzhSdElX?= =?utf-8?B?MHVxUDFXNnVZMVZieTU3SzBKa1pnc3dJSDFkbVV6REw3V0pZRkRkM044TXBy?= =?utf-8?B?ZVFDRDRNVi9zelVUVjFxRWM5VE5KbkZpMGdySFR0ZzZiWmlueUNJQzlrN0pH?= =?utf-8?B?Tmh0UlJrNmV6b0tRNExtam90aXhHak9aaDNxRVhIcGpRbFNOUVBST0FYWExB?= =?utf-8?B?V1ltUEVIRjJUQm1hWkxEeDJSRE9iVHBCT2o4Wms0UDduYlg5Ym5TeTRlWlNV?= =?utf-8?B?UDl2MG5qWFYyQmlMT0pmUnFTQWUwOEpPZnZFQ0RCclJRNWhlWGtEc242VndB?= =?utf-8?B?ZEE5MWdmN1Q5Y1VXeDhNZWJXNzBSNjAyc3RZdGhFWHBrN1Nwei9zRVUwdVV0?= =?utf-8?B?MnFYSVRKV2tHOTRFZzNTRmJiZzNDSHlnZTZOWTdnPT0=?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3350faf5-023f-4092-d272-08dbefeff0ca X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB4313.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Nov 2023 08:56:42.1307 (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: 8lznJaBr4HhcB5emR4xVGJu0ai+OGd08RK0F5QI2NTPe6dqu4jPPSjQyGgJmQS9bWeEt7D73kNPlMCW90DM44A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR10MB7376 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=2023-11-28_07,2023-11-27_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 suspectscore=0 spamscore=0 mlxlogscore=999 mlxscore=0 phishscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311280069 X-Proofpoint-GUID: 5bAyPVDMnnE44xU58OSS42dRpouXa_TI X-Proofpoint-ORIG-GUID: 5bAyPVDMnnE44xU58OSS42dRpouXa_TI Hi Christoph, >>> >>> Currently minimum granularity is the FS block size, but it should be >>> possibly to support lower in future. >> I really dislike how this forces aligned allocations.  Aligned >> allocations are a nice optimization to offload some of the work >> to the storage hard/firmware, but we need to support it in general. >> And I think with out of place writes into the COW fork, and atomic >> transactions to swap it in we can do that pretty easily. >> >> That should also allow to get rid of the horrible forcealign mode, >> as we can still try align if possible and just fall back to the >> out of place writes. >> Can you try to explain your idea a bit more? This is blocking us. Are you suggesting some sort of hybrid between the atomic write series you had a few years ago and this solution? To me that would be continuing with the following: - per-IO RWF_ATOMIC (and not O_ATOMIC semantics of nothing is written until some data sync) - writes must be a power-of-two and at a naturally-aligned offset - relying on atomic write HW support always But for extents which are misaligned, we CoW to a new extent? I suppose we would align that extent to alignment of the write (i.e. length of write). BTW, we also have rtvol support which does not use forcealign as it already can guarantee alignment, but still does rely on the same principle of requiring alignment - would you want CoW support there also? Thanks, John