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 X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=FORGED_MUA_MOZILLA, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61189C3F2D1 for ; Mon, 2 Mar 2020 08:10:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3AED72468E for ; Mon, 2 Mar 2020 08:10:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726390AbgCBIKS (ORCPT ); Mon, 2 Mar 2020 03:10:18 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:45772 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726313AbgCBIKS (ORCPT ); Mon, 2 Mar 2020 03:10:18 -0500 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02289SGq038487 for ; Mon, 2 Mar 2020 03:10:17 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yfnbeec48-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 02 Mar 2020 03:10:17 -0500 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 2 Mar 2020 08:10:10 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0228A9M757344066 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 2 Mar 2020 08:10:10 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E485DA4055; Mon, 2 Mar 2020 08:10:09 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8B710A4070; Mon, 2 Mar 2020 08:10:07 +0000 (GMT) Received: from [9.199.158.200] (unknown [9.199.158.200]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 2 Mar 2020 08:10:07 +0000 (GMT) Subject: Re: [PATCHv5 6/6] Documentation: Correct the description of FIEMAP_EXTENT_LAST To: Matthew Wilcox Cc: linux-ext4@vger.kernel.org, jack@suse.cz, tytso@mit.edu, adilger.kernel@dilger.ca, linux-fsdevel@vger.kernel.org, darrick.wong@oracle.com, hch@infradead.org, cmaiolino@redhat.com, david@fromorbit.com References: <5a00e8d4283d6849e0b8f408c8365b31fbc1d153.1582880246.git.riteshh@linux.ibm.com> <20200228153650.GG29971@bombadil.infradead.org> From: Ritesh Harjani Date: Mon, 2 Mar 2020 13:40:06 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200228153650.GG29971@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20030208-0028-0000-0000-000003DFD14E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20030208-0029-0000-0000-000024A4F937 Message-Id: <20200302081007.8B710A4070@d06av23.portsmouth.uk.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-03-02_02:2020-02-28,2020-03-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 mlxscore=0 impostorscore=0 phishscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003020063 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2/28/20 9:06 PM, Matthew Wilcox wrote: > On Fri, Feb 28, 2020 at 02:56:59PM +0530, Ritesh Harjani wrote: >> Currently FIEMAP_EXTENT_LAST is not working consistently across >> different filesystem's fiemap implementations. So add more information >> about how else this flag could set in other implementation. >> >> Also in general, user should not completely rely on this flag as >> such since it could return false value for e.g. >> when there is a delalloc extent which might get converted during >> writeback, immediately after the fiemap calls return. >> >> Signed-off-by: Ritesh Harjani >> --- >> Documentation/filesystems/fiemap.txt | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/filesystems/fiemap.txt b/Documentation/filesystems/fiemap.txt >> index f6d9c99103a4..fedfa9b9dde5 100644 >> --- a/Documentation/filesystems/fiemap.txt >> +++ b/Documentation/filesystems/fiemap.txt >> @@ -71,8 +71,7 @@ allocated is less than would be required to map the requested range, >> the maximum number of extents that can be mapped in the fm_extent[] >> array will be returned and fm_mapped_extents will be equal to >> fm_extent_count. In that case, the last extent in the array will not >> -complete the requested range and will not have the FIEMAP_EXTENT_LAST >> -flag set (see the next section on extent flags). >> +complete the requested range. > > This sentence still seems like it should be true. If the filesystem knows > there are more extents to come, it will definitely not set the LAST flag. > sure. >> @@ -96,7 +95,7 @@ block size of the file system. With the exception of extents flagged as >> FIEMAP_EXTENT_MERGED, adjacent extents will not be merged. >> >> The fe_flags field contains flags which describe the extent returned. >> -A special flag, FIEMAP_EXTENT_LAST is always set on the last extent in >> +A special flag, FIEMAP_EXTENT_LAST *may be* set on the last extent in >> the file so that the process making fiemap calls can determine when no >> more extents are available, without having to call the ioctl again. > > I'm not sure I'd highlight 'may be' here. Sure. > >> @@ -115,8 +114,9 @@ data. Note that the opposite is not true - it would be valid for >> FIEMAP_EXTENT_NOT_ALIGNED to appear alone. >> >> * FIEMAP_EXTENT_LAST >> -This is the last extent in the file. A mapping attempt past this >> -extent will return nothing. >> +This is generally the last extent in the file. A mapping attempt past this >> +extent may return nothing. In some implementations this flag is also set on >> +the last dataset queried by the user (via fiemap->fm_length). > > The word 'dataset' is used nowhere else in this document. How about > > "Some filesystems set this flag to indicate this extent is the last one in > the range queried by the user" Sure. Thanks for the review. Will make the suggested changes and send a v6. -ritesh