From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74294C433EF for ; Mon, 6 Jun 2022 20:35:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233953AbiFFUfQ (ORCPT ); Mon, 6 Jun 2022 16:35:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234069AbiFFUfE (ORCPT ); Mon, 6 Jun 2022 16:35:04 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 422CAAEE3E; Mon, 6 Jun 2022 13:34:34 -0700 (PDT) Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 256Gg39w030358; Mon, 6 Jun 2022 13:34:23 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=message-id : date : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding : mime-version; s=facebook; bh=wqia4cFWU7MiWeSV68qb33DY6RBTvzrDbiijaIM2pSU=; b=n9XVyeHtbR+ZG7Pe/0Y0tz8Xg1mWug+1R9PYHPVcgHGUbOxpIlKz72AsObdME2jdGM16 CPFJDog/ctic9kvRtdo/rz3feNb4eoZd7AVjKf4opNeTBSVcXm9suj4BviqXushYaG9t BQhJEGwY+IhxOb0WZQqG574K3dTZ8kWY/bI= Received: from nam10-dm6-obe.outbound.protection.outlook.com (mail-dm6nam10lp2104.outbound.protection.outlook.com [104.47.58.104]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3gg2qkk4xq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 06 Jun 2022 13:34:23 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=b5knZ9ZupzmXfSVTenrSgmXIn208vBnuiLLrR/gDi5r+TQNmpDQFF9RaRPjmovZ1lYrAh9A8gtwufX8PMo0mQTqiSri7yISSJflgehgZ34drj0w6m+0NOqd4Q+Cjpn/4hVRlDhuSMBnLrnGIhi9l4WFsSrFGqu+c2diwa6KHPM/dPcgoY9NxJHv/58uwcKMp96eNymh/wqeidgn32OFI9djbdvsltxBSLoHh7q/DTLKAf4MPf06o9sOVbfhTspLfQUu7H2nCaPQsJj0S5TKrM8EYq3fEfaqb5GTxbG7R+gy8yqbwGmTIAd6D/3L6rziczXi4Isofx4HVhHcYaKHusA== 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=wqia4cFWU7MiWeSV68qb33DY6RBTvzrDbiijaIM2pSU=; b=kEFUnxT5edla1Wen7rdZFNQp3xLE0+NYhITzyJHP9e2sHa5PV4pxuzW8KIBsxMV2TlBa6YUwDEo61MN4zqMScnbswtyPDi4Kr6beE85cNIjn9Rke5nyi+1Y6gJGhx0zU1DFxenNykHHpTS/kHzni7JRFu+uHehxc65/xoZ5qcmf2UmjPO9HeH9LPULrTzh6MXO/PHxCClubcsMugMUMur2imcyuHMVdi5omKyZP+WqvUArd0iHvXzEouMmeJAtqjqsThfv2lWz4zpLo7xeLzYvYID2dhyrExdcQLB3o8yGKnBU9oz2Uoc5SDUqvk47z8kEgan2lSe2YUQjMSUuMaDA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=fb.com; dmarc=pass action=none header.from=fb.com; dkim=pass header.d=fb.com; arc=none Received: from MWHPR15MB1791.namprd15.prod.outlook.com (2603:10b6:301:4e::20) by SA1PR15MB4372.namprd15.prod.outlook.com (2603:10b6:806:193::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5314.19; Mon, 6 Jun 2022 20:34:21 +0000 Received: from MWHPR15MB1791.namprd15.prod.outlook.com ([fe80::e17e:e90d:7675:24b8]) by MWHPR15MB1791.namprd15.prod.outlook.com ([fe80::e17e:e90d:7675:24b8%11]) with mapi id 15.20.5314.019; Mon, 6 Jun 2022 20:34:21 +0000 Message-ID: <6a21584a-34d6-9691-138c-90df23fa727b@fb.com> Date: Mon, 6 Jun 2022 13:34:18 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v7 06/15] iomap: Return error code from iomap_write_iter() Content-Language: en-US To: Matthew Wilcox Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, david@fromorbit.com, jack@suse.cz, hch@infradead.org, axboe@kernel.dk References: <20220601210141.3773402-1-shr@fb.com> <20220601210141.3773402-7-shr@fb.com> <0f83316c-3aa2-3cb6-ede1-c2dd2dd3ab31@fb.com> <4c15cc6f-97a6-ab53-6b1c-871058608419@fb.com> <8a7c76d2-3cb4-0162-584a-69b130831c3e@fb.com> From: Stefan Roesch In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR03CA0090.namprd03.prod.outlook.com (2603:10b6:a03:331::35) To MWHPR15MB1791.namprd15.prod.outlook.com (2603:10b6:301:4e::20) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: df02ba05-fa00-4e36-0c7d-08da47fbefc6 X-MS-TrafficTypeDiagnostic: SA1PR15MB4372:EE_ X-Microsoft-Antispam-PRVS: X-FB-Source: Internal 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:MWHPR15MB1791.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(31696002)(6486002)(31686004)(66556008)(8936002)(186003)(508600001)(5660300002)(66476007)(4326008)(2616005)(8676002)(66946007)(6506007)(38100700002)(6916009)(6666004)(2906002)(316002)(6512007)(36756003)(86362001)(53546011)(43740500002)(45980500001);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cldLK0NEMWJQNnFyU2dhS3YrSkFyd2g5c3V3enFUT2RQSi9Rb3gyaW9kaUtT?= =?utf-8?B?azhaY2MvWExMYW9QQzQ1ZDJDSzRTSnNyRTZMWGo4RU5sbDlQazc3OFVmWG4y?= =?utf-8?B?dkdoQVlRREhaVUtJS1BZNnhPUFEwWThWRTZwckFNZ1huUEJiVjRMNk1rbHVU?= =?utf-8?B?TjNtVm9aR2xTQVZNL3p1WlViWjhMRDNBZjVyeENuVG9YalRwbTZzQ3lOWm0x?= =?utf-8?B?LzJoZ3FQSUVwVDdTU2xxUC9DNmtVekM5WW5CcllLUVgrVkV1ZjJtYVA4YkUv?= =?utf-8?B?YUxmeEU2Zk1oNTRXQXJVNTJLWGhaVlVGbE94QXhXTk1WaFh4NkhTTUpOMlA3?= =?utf-8?B?MjRNY1d0b3hzUWF0NFMwMmo0VFNGK0hIWTlBemZwN0ovWC9NalJuYnRNaE9M?= =?utf-8?B?TDY0aERnSG5YajFrc2NYT3pKZmQvbFdWU0owQ3Jud2RlYyt4NXZ2MVE5b2VK?= =?utf-8?B?T1dUNFZjWlJuemY4b0Z2alg4Mk9xeGZscEtweHI4YWFvZDZmeTI0OWt6dHNv?= =?utf-8?B?a1RPNGw5MlJNM1VLWUdVUGxXZ3hnaFhhM0ppWGIrcHF3VGhMT09JOXMvdlZD?= =?utf-8?B?NE1qTis3UzBaZ1licVVDZW5JK3krLzl4RDJPTjNNL3ErWkR3cUZxeWJNQVAr?= =?utf-8?B?bEdCRlo5SFZacWtxUkp4YWhGUEVBSWNabVdiUGoyNkErS0Npa2RScGdwdWRX?= =?utf-8?B?TFNRYWd2dHJDYXEvZW5NclcraDAzc0Vnd2JoYmRtZjdIQXppcjBsaDZiOEFZ?= =?utf-8?B?TkZpT0xha1ByY0dvUlZlb3RqOFZwdlUwa3ExQXJBcGJoVTMxYnFsajdsa0Rm?= =?utf-8?B?SEpVQmRXOUtGdXdaYnFQQ0E4Qnc0TGVVd3JCZ0loKzdiQWM2NmMxMVR4YWJC?= =?utf-8?B?MUcyUG1vT2UwdWZpaXgvNmhqdXlBSWV2Y2RtMmlMOW12bjZIL2NpdVRhakJD?= =?utf-8?B?L253MUxkdHlZRXVSamxzUFhwWEw0eTJQcFFNSURMK0xXR1Y4endqQnZIZCtX?= =?utf-8?B?RWVYZklpclc5M2lLUHRmQzMxMFhlSm90ejJqQnkwdkdGMG5pSVVoY25kaUZL?= =?utf-8?B?ZWhxT1FzU0JDZjNTK2JScUlrcExUdzhXLzdST2x2YmZiUit2Q0YzUWRQS1hq?= =?utf-8?B?bkhydTRjek9EdCtnYnJ3OWxaRzU3SWpaL0ROenErV0srMDIvYzd0QzhSeHZx?= =?utf-8?B?WU51TVFkVjRCK0xvcC9rZ2pVTUZ4d25iQ2V5aUdwRzVialFnWklVY2QralBW?= =?utf-8?B?Q3ZMQ3lmOFBHNEVVUDNRd0RWNzlZRHFNYTN1bWRrejB5cFBqV3VoNTJLZ0pu?= =?utf-8?B?V3N0VVB3OTYvbG85YzB4Z2FmdWRNYTJJWnJ3bTA5d09aRXhJakNpN0JMaHJS?= =?utf-8?B?VzRrazRBd0V6NXRWRnNWV3VqZUFtbzRvWUk2ZXMvamY5MjErZGFNTXR1ZUo3?= =?utf-8?B?R3Rsb3U2dmNMbkpPYjRCbXJEUHB4R0pZbUdveTNCRjdQQjQ2REt2YTc2MzJ2?= =?utf-8?B?bW8yUEwyVnFPbjNHZkdhOW9hTnlZU3E2NGhnQzM0Z3hIL3hyUWxBT0JiOHZt?= =?utf-8?B?dzBCUVlSNzhHRzQ4M254YkJ5cVdYeW5CNkdrY1pVc2V4VTRqZjh5TXBueWda?= =?utf-8?B?SEVQOGtJWTI2a3V6Y3NndDlqdE9PUi8yUDdZaXdXRHZSMUFNTVhiMTZRaVI2?= =?utf-8?B?TERHQlh0dzBJU2pYaWhxSk1ZcVpwRStPaVZYWG5tZ05MWjlnUktFZ0IyTXZ6?= =?utf-8?B?b2t2Y2tnZEZ1L0tWRmk0UU1ydTcxRW0xYUkxVGxlVkRCazVZMUEyZVMzYnQz?= =?utf-8?B?SmhydCtGNWM0ZHc4cTJIUEg4M3JKZlIvT2RrSWRxcis5bzVUNmwyTTBQdWxZ?= =?utf-8?B?WUlTSitpYkh3bnQvMjNGd096WnNzUnpaUkdRYXFNalRJcStCWVFZQmplSDNq?= =?utf-8?B?eTNXWG9MVTJxUnhuakpEQ2ZGc2lwZDlLMUZGTkUrSmYyRE91SVdDd1hKU1Bq?= =?utf-8?B?VnVOSDI1MEl5ZEpVRWFDa2RKSk81QlRaQlkrekxrMHkxaDVJeWFjZU00NDY5?= =?utf-8?B?QlpyNDlHZFlsUG5lQmJha0VjMDcvQmU2VkVqN3o0SW1lcmcxc2p2VnVlR3Vr?= =?utf-8?B?bk9HOXAvb3Z0RGxJank4cTZmWk4veHZBczFyOVlzVkwxRDV1Q1Q3N2hoVXYw?= =?utf-8?B?RGlvKzFVNmQ1NnM0Ly9qMFd6VzVyMEtQdlZXQUQ1SHNONmZBdGdQU1lhQ1No?= =?utf-8?B?RG1Pa2RNdExjRFBOanJ6bXp4RFJxR2ovY0R4OEx6ZVNJU2Y1SHlnUWJEbC9I?= =?utf-8?B?dTNuVUdFaFNtSVdlemJSV0J2VlltdjZwYVgwYlYydkhCVkh1bE4rbS83V3Z6?= =?utf-8?Q?YDHJixI5cdrXTsWY=3D?= X-OriginatorOrg: fb.com X-MS-Exchange-CrossTenant-Network-Message-Id: df02ba05-fa00-4e36-0c7d-08da47fbefc6 X-MS-Exchange-CrossTenant-AuthSource: MWHPR15MB1791.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jun 2022 20:34:21.3162 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: xh6ozY7X8ElOonsq7s1pdWnr5WcFZQhwbPw7xqbimqv+pXem4R0joImN6zOY6A5+ X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB4372 X-Proofpoint-ORIG-GUID: HQfOtflN2dmbZSUd0N1ybtrHUfMoN-1B X-Proofpoint-GUID: HQfOtflN2dmbZSUd0N1ybtrHUfMoN-1B X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-06-06_06,2022-06-03_01,2022-02-23_01 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 6/6/22 1:30 PM, Matthew Wilcox wrote: > On Mon, Jun 06, 2022 at 12:28:04PM -0700, Stefan Roesch wrote: >> On 6/6/22 12:25 PM, Matthew Wilcox wrote: >>> On Mon, Jun 06, 2022 at 12:21:28PM -0700, Stefan Roesch wrote: >>>> On 6/6/22 12:18 PM, Matthew Wilcox wrote: >>>>> On Mon, Jun 06, 2022 at 09:39:03AM -0700, Stefan Roesch wrote: >>>>>> On 6/2/22 5:38 AM, Matthew Wilcox wrote: >>>>>>> On Wed, Jun 01, 2022 at 02:01:32PM -0700, Stefan Roesch wrote: >>>>>>>> Change the signature of iomap_write_iter() to return an error code. In >>>>>>>> case we cannot allocate a page in iomap_write_begin(), we will not retry >>>>>>>> the memory alloction in iomap_write_begin(). >>>>>>> >>>>>>> loff_t can already represent an error code. And it's already used like >>>>>>> that. >>>>>>> >>>>>>>> @@ -829,7 +830,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) >>>>>>>> length -= status; >>>>>>>> } while (iov_iter_count(i) && length); >>>>>>>> >>>>>>>> - return written ? written : status; >>>>>>>> + *processed = written ? written : error; >>>>>>>> + return error; >>>>>>> >>>>>>> I think the change you really want is: >>>>>>> >>>>>>> if (status == -EAGAIN) >>>>>>> return -EAGAIN; >>>>>>> if (written) >>>>>>> return written; >>>>>>> return status; >>>>>>> >>>>>> >>>>>> I think the change needs to be: >>>>>> >>>>>> - return written ? written : status; >>>>>> + if (status == -EAGAIN) { >>>>>> + iov_iter_revert(i, written); >>>>>> + return -EAGAIN; >>>>>> + } >>>>>> + if (written) >>>>>> + return written; >>>>>> + return status; >>>>> >>>>> Ah yes, I think you're right. >>>>> >>>>> Does it work to leave everything the way it is, call back into the >>>>> iomap_write_iter() after having done a short write, get the -EAGAIN at >>>>> that point and pass the already-advanced iterator to the worker thread? >>>>> I haven't looked into the details of how that works, so maybe you just >>>>> can't do that. >>>> >>>> With the above change, short writes are handled correctly. >>> >>> Are they though? What about a write that crosses an extent boundary? >>> iomap_write_iter() gets called once per extent and I have a feeling that >>> you really need to revert the entire write, rather than just the part >>> of the write that was to that extent. >>> >>> Anyway, my question was whether we need to revert or whether the worker >>> thread can continue from where we left off. >> >> Without iov_iter_revert() fsx fails with errors in short writes and also my test >> program which issues short writes fails. > > Does your test program include starting in one extent, completing the > portion of the write which is in that extent successfully, and having > the portion of the write which is in the second extent be short? I do a 3k write, where the first 2k write is serviced from one extent and the last 1k is served from another extent. Does that answer the question?