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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 A4BD3C4646B for ; Tue, 25 Jun 2019 03:06:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E57620663 for ; Tue, 25 Jun 2019 03:06:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="BXJlUqAK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728088AbfFYDGQ (ORCPT ); Mon, 24 Jun 2019 23:06:16 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:44288 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726461AbfFYDGQ (ORCPT ); Mon, 24 Jun 2019 23:06:16 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5P2xZkP183824; Tue, 25 Jun 2019 03:04:56 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=y1nTqvm5zm2oVuuxHsrGpbU4gEqHpmqSXspC8Bne9NM=; b=BXJlUqAKvMETApXDcsKgEZiNdrmlXkQGnY88kMW3AMxNKcXyyaE6UXAlpYECy+ntv7pH 6uhEP1tj4tycY9LMVwQSwCJ1OFoN8XiURaWWP5MgMDhRGeWBYKJ5F+hDMXeWyXvzw09Y W93kGqDhXdEUxHJGprg0ZqzGMSQuXc6a6uPIBselde0/QnSPFrNudLSF4JrDCRjZHlSe PtPwNFzZ3qhrAqfZeA252/OTt3UOJ6W5XclgLFaB43nqCHJq7hk5QCcLKtksxGRz16et vcWpg2Ca0sMBi64yleW6uVf2BPJY2qw2eabFh6Nu+9cNmwvp3CwrP4l2harCRSOmeEeb 1g== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 2t9brt1hg7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Jun 2019 03:04:56 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5P34h96101926; Tue, 25 Jun 2019 03:04:55 GMT Received: from pps.reinject (localhost [127.0.0.1]) by aserp3020.oracle.com with ESMTP id 2t9p6tx2qw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 25 Jun 2019 03:04:55 +0000 Received: from aserp3020.oracle.com (aserp3020.oracle.com [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x5P34tbP102400; Tue, 25 Jun 2019 03:04:55 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 2t9p6tx2qp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Jun 2019 03:04:54 +0000 Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x5P34gx0001788; Tue, 25 Jun 2019 03:04:42 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 24 Jun 2019 20:04:41 -0700 Date: Mon, 24 Jun 2019 20:04:39 -0700 From: "Darrick J. Wong" To: Jan Kara Cc: linux-efi@vger.kernel.org, linux-btrfs@vger.kernel.org, yuchao0@huawei.com, linux-mm@kvack.org, clm@fb.com, adilger.kernel@dilger.ca, matthew.garrett@nebula.com, linux-nilfs@vger.kernel.org, linux-ext4@vger.kernel.org, devel@lists.orangefs.org, josef@toxicpanda.com, reiserfs-devel@vger.kernel.org, viro@zeniv.linux.org.uk, dsterba@suse.com, jaegeuk@kernel.org, tytso@mit.edu, ard.biesheuvel@linaro.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, jk@ozlabs.org, jack@suse.com, linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com Subject: Re: [Ocfs2-devel] [PATCH 2/7] vfs: flush and wait for io when setting the immutable flag via SETFLAGS Message-ID: <20190625030439.GA5379@magnolia> References: <156116141046.1664939.11424021489724835645.stgit@magnolia> <156116142734.1664939.5074567130774423066.stgit@magnolia> <20190624113737.GG32376@quack2.suse.cz> <20190624215817.GE1611011@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190624215817.GE1611011@magnolia> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9298 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906250023 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jun 24, 2019 at 02:58:17PM -0700, Darrick J. Wong wrote: > On Mon, Jun 24, 2019 at 01:37:37PM +0200, Jan Kara wrote: > > On Fri 21-06-19 16:57:07, Darrick J. Wong wrote: > > > From: Darrick J. Wong > > > > > > When we're using FS_IOC_SETFLAGS to set the immutable flag on a file, we > > > need to ensure that userspace can't continue to write the file after the > > > file becomes immutable. To make that happen, we have to flush all the > > > dirty pagecache pages to disk to ensure that we can fail a page fault on > > > a mmap'd region, wait for pending directio to complete, and hope the > > > caller locked out any new writes by holding the inode lock. > > > > > > Signed-off-by: Darrick J. Wong > > > > Seeing the way this worked out, is there a reason to have separate > > vfs_ioc_setflags_flush_data() instead of folding the functionality in > > vfs_ioc_setflags_check() (possibly renaming it to > > vfs_ioc_setflags_prepare() to indicate it does already some changes)? I > > don't see any place that would need these two separated... > > XFS needs them to be separated. > > If we even /think/ that we're going to be setting the immutable flag > then we need to grab the IOLOCK and the MMAPLOCK to prevent further > writes while we drain all the directio writes and dirty data. IO > completions for the write draining can take the ILOCK, which means that > we can't have grabbed it yet. > > Next, we grab the ILOCK so we can check the new flags against the inode > and then update the inode core. > > For most filesystems I think it suffices to inode_lock and then do both, > though. Heh, lol, that applies to fssetxattr, not to setflags, because xfs setflags implementation open-codes the relevant fssetxattr pieces. So for setflags we can combine both parts into a single _prepare function. --D > > > +/* > > > + * Flush all pending IO and dirty mappings before setting S_IMMUTABLE on an > > > + * inode via FS_IOC_SETFLAGS. If the flush fails we'll clear the flag before > > > + * returning error. > > > + * > > > + * Note: the caller should be holding i_mutex, or else be sure that > > > + * they have exclusive access to the inode structure. > > > + */ > > > +static inline int vfs_ioc_setflags_flush_data(struct inode *inode, int flags) > > > +{ > > > + int ret; > > > + > > > + if (!vfs_ioc_setflags_need_flush(inode, flags)) > > > + return 0; > > > + > > > + inode_set_flags(inode, S_IMMUTABLE, S_IMMUTABLE); > > > + ret = inode_flush_data(inode); > > > + if (ret) > > > + inode_set_flags(inode, 0, S_IMMUTABLE); > > > + return ret; > > > +} > > > > Also this sets S_IMMUTABLE whenever vfs_ioc_setflags_need_flush() returns > > true. That is currently the right thing but seems like a landmine waiting > > to trip? So I'd just drop the vfs_ioc_setflags_need_flush() abstraction to > > make it clear what's going on. > > Ok. > > --D > > > > > Honza > > -- > > Jan Kara > > SUSE Labs, CR > > _______________________________________________ > Ocfs2-devel mailing list > Ocfs2-devel@oss.oracle.com > https://oss.oracle.com/mailman/listinfo/ocfs2-devel