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,URIBL_BLOCKED,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 63F15C432C0 for ; Tue, 26 Nov 2019 08:34:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36EB020748 for ; Tue, 26 Nov 2019 08:34:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727518AbfKZIex (ORCPT ); Tue, 26 Nov 2019 03:34:53 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:28816 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725943AbfKZIex (ORCPT ); Tue, 26 Nov 2019 03:34:53 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xAQ8QdsQ093871 for ; Tue, 26 Nov 2019 03:34:52 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 2wfju94w6x-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 26 Nov 2019 03:34:51 -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) Tue, 26 Nov 2019 08:34:46 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xAQ8YjDC35914064 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Nov 2019 08:34:46 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9A2CA405F; Tue, 26 Nov 2019 08:34:45 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1FD5A405B; Tue, 26 Nov 2019 08:34:43 +0000 (GMT) Received: from [9.199.158.76] (unknown [9.199.158.76]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 26 Nov 2019 08:34:43 +0000 (GMT) Subject: Re: [PATCH] f2fs: Fix direct IO handling To: Damien Le Moal , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Jaegeuk Kim , Chao Yu Cc: linux-fsdevel@vger.kernel.org, Javier Gonzalez , Shinichiro Kawasaki References: <20191126075719.1046485-1-damien.lemoal@wdc.com> From: Ritesh Harjani Date: Tue, 26 Nov 2019 14:04:43 +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: <20191126075719.1046485-1-damien.lemoal@wdc.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19112608-0028-0000-0000-000003C017DE X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19112608-0029-0000-0000-000024831879 Message-Id: <20191126083443.F1FD5A405B@b06wcsmtp001.portsmouth.uk.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-26_01:2019-11-21,2019-11-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 clxscore=1015 bulkscore=0 adultscore=0 priorityscore=1501 malwarescore=0 spamscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911260076 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hello Damien, IIUC, you are trying to fix a stale data read by DIO read for the case you explained in your patch w.r.t. DIO-write forced to write as buffIO. Coincidentally I was just looking at the same code path just now. So I do have a query to you/f2fs group. Below could be silly one, as I don't understand F2FS in great detail. How is the stale data by DIO read, is protected against a mmap writes via f2fs_vm_page_mkwrite? f2fs_vm_page_mkwrite() f2fs_direct_IO (read) filemap_write_and_wait_range() -> f2fs_get_blocks() -> submit_bio() -> set_page_dirty() Is above race possible with current f2fs code? i.e. f2fs_direct_IO could read the stale data from the blocks which were allocated due to mmap fault? Am I missing something here? -ritesh On 11/26/19 1:27 PM, Damien Le Moal wrote: > f2fs_preallocate_blocks() identifies direct IOs using the IOCB_DIRECT > flag for a kiocb structure. However, the file system direct IO handler > function f2fs_direct_IO() may have decided that a direct IO has to be > exececuted as a buffered IO using the function f2fs_force_buffered_io(). > This is the case for instance for volumes including zoned block device > and for unaligned write IOs with LFS mode enabled. > > These 2 different methods of identifying direct IOs can result in > inconsistencies generating stale data access for direct reads after a > direct IO write that is treated as a buffered write. Fix this > inconsistency by combining the IOCB_DIRECT flag test with the result > of f2fs_force_buffered_io(). > > Reported-by: Javier Gonzalez > Signed-off-by: Damien Le Moal > --- > fs/f2fs/data.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index 5755e897a5f0..8ac2d3b70022 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from) > int flag; > int err = 0; > bool direct_io = iocb->ki_flags & IOCB_DIRECT; > + bool do_direct_io = direct_io && > + !f2fs_force_buffered_io(inode, iocb, from); > > /* convert inline data for Direct I/O*/ > if (direct_io) { > @@ -1081,7 +1083,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from) > return err; > } > > - if (direct_io && allow_outplace_dio(inode, iocb, from)) > + if (do_direct_io && allow_outplace_dio(inode, iocb, from)) > return 0; > > if (is_inode_flag_set(inode, FI_NO_PREALLOC)) >