From: Ira Weiny <ira.weiny@intel.com> To: David Laight <David.Laight@ACULAB.COM> Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Alexander Viro <viro@zeniv.linux.org.uk>, "Darrick J. Wong" <darrick.wong@oracle.com>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, Christoph Hellwig <hch@lst.de>, "Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>, "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>, "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org> Subject: Re: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed Date: Wed, 15 Jan 2020 09:53:15 -0800 Message-ID: <20200115175315.GC23311@iweiny-DESK2.sc.intel.com> (raw) In-Reply-To: <06258747f6824a35adfaa999ab4c2261@AcuMS.aculab.com> On Wed, Jan 15, 2020 at 10:21:45AM +0000, David Laight wrote: > From ira.weiny@intel.com > > Sent: 10 January 2020 19:30 > > > > Page faults need to ensure the inode mode is correct and consistent with > > the vmf information at the time of the fault. There is no easy way to > > ensure the vmf information is correct if a mode change is in progress. > > Furthermore, there is no good use case to require a mode change while > > the file is mmap'ed. > > > > Track mmap's of the file and fail the mode change if the file is > > mmap'ed. > > This seems wrong to me. > I presume the 'mode changes' are from things like 'chmod -w ...'. No... Sorry... "mode" was a _very_ bad name. In this context "mode" was the "DAX mode" not the file mode. > mmap() should be no different to open(). > Only the permissions set when the file is opened count. > > Next you'll be stopping unlink() when a file is open :-) hehehe :-D no ... sorry that was not the meaning. To be clear what this is preventing is a change from non-DAX to DAX or vice versa while a file is mmap'ed. I'm looking at a better name for this. For this commit message is this more clear? <commit> fs: Prevent DAX change if file is mmap'ed Page faults need to ensure the inode DAX configuration is correct and consistent with the vmf information at the time of the fault. There is no easy way to ensure the vmf information is correct if a DAX change is in progress. Furthermore, there is no good use case to require changing DAX configs while the file is mmap'ed. Track mmap's of the file and fail the DAX change if the file is mmap'ed. </commit> Sorry for the confusion, Ira > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
next prev parent reply index Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-10 19:29 [RFC PATCH V2 00/12] Enable per-file/directory DAX operations V2 ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute ira.weiny 2020-01-15 11:37 ` Jan Kara 2020-01-15 17:38 ` Darrick J. Wong 2020-01-15 19:45 ` Ira Weiny 2020-01-15 20:10 ` Dan Williams 2020-01-15 22:38 ` Ira Weiny 2020-01-16 5:39 ` Darrick J. Wong 2020-01-16 6:05 ` Dan Williams 2020-01-16 6:18 ` Darrick J. Wong 2020-01-16 6:25 ` Dan Williams 2020-01-18 9:11 ` Dave Chinner 2020-01-16 17:55 ` Ira Weiny 2020-01-16 18:04 ` Darrick J. Wong 2020-01-16 18:52 ` Ira Weiny 2020-01-16 22:19 ` Darrick J. Wong 2020-01-17 11:58 ` Jan Kara 2020-01-10 19:29 ` [RFC PATCH V2 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 04/12] fs/xfs: Clean up DAX support check ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 05/12] fs: remove unneeded IS_DAX() check ira.weiny 2020-01-16 9:38 ` Jan Kara 2020-01-16 18:47 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 07/12] fs: Add locking for a dynamic inode 'mode' ira.weiny 2020-01-13 22:12 ` Darrick J. Wong 2020-01-14 0:20 ` Ira Weiny 2020-01-14 1:03 ` Darrick J. Wong 2020-01-15 19:08 ` Ira Weiny 2020-01-16 5:40 ` Darrick J. Wong 2020-01-16 18:54 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs ira.weiny 2020-01-13 22:19 ` Darrick J. Wong 2020-01-14 0:35 ` Ira Weiny 2020-01-15 0:57 ` Ira Weiny 2020-01-15 23:52 ` Ira Weiny 2020-01-16 9:24 ` Jan Kara 2020-01-16 19:12 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed ira.weiny 2020-01-13 22:22 ` Darrick J. Wong 2020-01-14 0:46 ` Ira Weiny 2020-01-14 1:30 ` Darrick J. Wong 2020-01-14 17:53 ` Ira Weiny 2020-01-15 11:34 ` Jan Kara 2020-01-15 18:24 ` Ira Weiny 2020-01-15 10:21 ` David Laight 2020-01-15 17:53 ` Ira Weiny [this message] 2020-01-10 19:29 ` [RFC PATCH V2 10/12] fs/xfs: Fix truncate up ira.weiny 2020-01-13 22:27 ` Darrick J. Wong 2020-01-14 0:40 ` Ira Weiny 2020-01-14 1:14 ` Darrick J. Wong 2020-01-14 19:00 ` Ira Weiny 2020-01-14 19:39 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
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