From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp2120.oracle.com ([156.151.31.85]:47688 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727053AbfDEA3j (ORCPT ); Thu, 4 Apr 2019 20:29:39 -0400 Date: Thu, 4 Apr 2019 17:29:29 -0700 From: "Darrick J. Wong" Subject: Re: [PATCH 2/3] xfs: reset page mappings after setting immutable Message-ID: <20190405002929.GD1177@magnolia> References: <155379543409.24796.5783716624820175068.stgit@magnolia> <155379544747.24796.1807309281507099911.stgit@magnolia> <20190328212147.GK23020@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190328212147.GK23020@dastard> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dave Chinner Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org On Fri, Mar 29, 2019 at 08:21:47AM +1100, Dave Chinner wrote: > On Thu, Mar 28, 2019 at 10:50:47AM -0700, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > The chattr manpage has this to say about immutable files: > > > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > > or renamed, no link can be created to this file, most of the file's > > metadata can not be modified, and the file can not be opened in write > > mode." > > > > This means that we need to flush the page cache when setting the > > nit: flush and invalidate the page cache. > > > immutable flag so that programs cannot continue to write to writable > > mappings. > > Do we even need to invalidate the page cache for this? i.e. we've > cleaned the pages so that any new write to them will fault, > that will see the immutable flag via ->page_mkwrite and then the > app should segv, right? Yeah, we only need to flush the pages. No need to invalidate. > > Signed-off-by: Darrick J. Wong > > --- > > fs/xfs/xfs_ioctl.c | 63 +++++++++++++++++++++++++++++++++++----------------- > > 1 file changed, 43 insertions(+), 20 deletions(-) > > > > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > > index 6ecdbb3af7de..2bd1c5ab5008 100644 > > --- a/fs/xfs/xfs_ioctl.c > > +++ b/fs/xfs/xfs_ioctl.c > > @@ -998,6 +998,37 @@ xfs_diflags_to_linux( > > #endif > > } > > > > +static int > > +xfs_ioctl_setattr_flush( > > + struct xfs_inode *ip, > > + int *join_flags) > > +{ > > + struct inode *inode = VFS_I(ip); > > + int error; > > + > > + if (S_ISDIR(inode->i_mode)) > > + return 0; > > + if ((*join_flags) & (XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL)) > > + return 0; > > + > > + /* lock, flush and invalidate mapping in preparation for flag change */ > > + xfs_ilock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL); > > + error = filemap_write_and_wait(inode->i_mapping); > > + if (error) > > + goto out_unlock; > > + error = invalidate_inode_pages2(inode->i_mapping); > > + if (error) > > + goto out_unlock; > > + > > + *join_flags = XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL; > > + return 0; > > + > > +out_unlock: > > + xfs_iunlock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL); > > + return error; > > + > > +} > > Doesn't wait for direct IO to drain. Wouldn't it be better to do > this? > > lock() > xfs_flush_unmap_range(ip, 0, XFS_SIZE(ip)); > unlock() But if we only need to filemap_write_and_wait, then calling flush_unmap (which also calls truncate_pagecache_range) is too much work. --D > > Otherwise looks ok. > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com