From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jeff Layton <jlayton@poochiereds.net>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Dave Chinner <david@fromorbit.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"J. Bruce Fields" <bfields@fieldses.org>,
Linux MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-xfs@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 6/7] mm, fs: introduce file_operations->post_mmap()
Date: Tue, 26 Sep 2017 15:06:45 -0600 [thread overview]
Message-ID: <20170926210645.GA7798@linux.intel.com> (raw)
In-Reply-To: <CAPcyv4iVc9y8PE24ZvkiBYdp4Die0Q-K5S6QexW_6YQ_M0F4QA@mail.gmail.com>
On Tue, Sep 26, 2017 at 12:19:21PM -0700, Dan Williams wrote:
> On Tue, Sep 26, 2017 at 11:57 AM, Ross Zwisler
<>
> > This decision can only be made (in this
> > proposed scheme) *after* the inode->i_mapping->i_mmap tree has been
> > populated, which means we need another call into the filesystem after this
> > insertion has happened.
>
> I get that, but it seems over-engineered and something that can also
> be safely cleaned up after the fact by the code path that is disabling
> DAX.
I don't think you can safely clean it up after the fact because some thread
might have already called ->mmap() to set up the vma->vm_flags for their new
mapping, but they haven't added it to inode->i_mapping->i_mmap.
The inode->i_mapping->i_mmap tree is the only way (that I know of at least)
that the filesystem has any idea about about the mapping. This is the method
by which we would try and clean up mapping flags, if we were to do so, and
it's the only way that the filesystem can know whether or not mappings exist.
The only way that I could think of to make this safely work is to have the
insertion into the inode->i_mapping->i_mmap tree be our sync point. After
that the filesystem and the mapping code can communicate on the state of DAX,
but before that I think it's basically indeterminate.
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next prev parent reply other threads:[~2017-09-26 21:03 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-25 23:13 [PATCH 0/7] re-enable XFS per-inode DAX Ross Zwisler
2017-09-25 23:13 ` [PATCH 1/7] xfs: always use DAX if mount option is used Ross Zwisler
2017-09-25 23:38 ` Dave Chinner
2017-09-26 9:35 ` Jan Kara
2017-09-26 11:09 ` Dave Chinner
2017-09-26 14:37 ` Christoph Hellwig
2017-09-26 17:30 ` Ross Zwisler
2017-09-26 19:48 ` Darrick J. Wong
2017-09-26 22:00 ` Dave Chinner
2017-09-27 6:40 ` Christoph Hellwig
2017-09-27 16:15 ` Ross Zwisler
2017-10-01 8:17 ` Christoph Hellwig
2017-09-26 18:02 ` Eric Sandeen
2017-09-26 18:50 ` Ross Zwisler
2017-09-25 23:13 ` [PATCH 2/7] xfs: validate bdev support for DAX inode flag Ross Zwisler
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 17:16 ` Ross Zwisler
2017-09-26 17:57 ` Darrick J. Wong
2017-09-25 23:14 ` [PATCH 3/7] xfs: protect S_DAX transitions in XFS read path Ross Zwisler
2017-09-25 23:27 ` Dave Chinner
2017-09-26 6:32 ` Christoph Hellwig
2017-09-26 13:59 ` Dan Williams
2017-09-26 14:33 ` Christoph Hellwig
2017-09-26 18:11 ` Dan Williams
2017-10-01 8:17 ` Christoph Hellwig
2017-09-25 23:14 ` [PATCH 4/7] xfs: protect S_DAX transitions in XFS write path Ross Zwisler
2017-09-25 23:29 ` Dave Chinner
2017-09-25 23:14 ` [PATCH 5/7] xfs: introduce xfs_is_dax_state_changing Ross Zwisler
2017-09-26 6:33 ` Christoph Hellwig
2017-09-25 23:14 ` [PATCH 6/7] mm, fs: introduce file_operations->post_mmap() Ross Zwisler
2017-09-25 23:38 ` Dan Williams
2017-09-26 18:57 ` Ross Zwisler
2017-09-26 19:19 ` Dan Williams
2017-09-26 21:06 ` Ross Zwisler [this message]
2017-09-26 21:41 ` Dan Williams
2017-09-27 11:35 ` Jan Kara
2017-09-27 14:00 ` Dan Williams
2017-09-27 15:07 ` Jan Kara
2017-09-27 15:36 ` Dan Williams
2017-09-27 15:39 ` Ross Zwisler
2017-09-27 15:54 ` Dan Williams
2017-09-26 6:34 ` Christoph Hellwig
2017-09-25 23:14 ` [PATCH 7/7] xfs: re-enable XFS per-inode DAX Ross Zwisler
2017-09-26 0:31 ` Dave Chinner
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 19:01 ` Ross Zwisler
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