From: Dave Chinner <david@fromorbit.com>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jeff Layton <jlayton@poochiereds.net>, Jan Kara <jack@suse.cz>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
"J. Bruce Fields" <bfields@fieldses.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-xfs@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 4/7] xfs: protect S_DAX transitions in XFS write path
Date: Tue, 26 Sep 2017 09:29:45 +1000 [thread overview]
Message-ID: <20170925232945.GL10955@dastard> (raw)
In-Reply-To: <20170925231404.32723-5-ross.zwisler@linux.intel.com>
On Mon, Sep 25, 2017 at 05:14:01PM -0600, Ross Zwisler wrote:
> In the current XFS write I/O path we check IS_DAX() in
> xfs_file_write_iter() to decide whether to do DAX I/O, direct I/O or
> buffered I/O. This check is done without holding the XFS_IOLOCK, though,
> which means that if we allow S_DAX to be manipulated via the inode flag we
> can run into this race:
>
> CPU 0 CPU 1
> ----- -----
> xfs_file_write_iter()
> IS_DAX() << returns false
> xfs_ioctl_setattr()
> xfs_ioctl_setattr_dax_invalidate()
> xfs_ilock(XFS_MMAPLOCK|XFS_IOLOCK)
> sets S_DAX
> releases XFS_MMAPLOCK and XFS_IOLOCK
> xfs_file_buffered_aio_write()
> does buffered I/O to DAX inode, death
>
> Fix this by ensuring that we only check S_DAX when we hold the XFS_IOLOCK
> in the write path.
NACK. This breaks concurrent direct IO write semantics. We must not
take XFS_IOLOCK_EXCL on direct IO writes unless it is absolutely
necessary - there are lots of applications out there that rely on
these semantics for performance.
CHeers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
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Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>,
Jeff Layton <jlayton@poochiereds.net>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 4/7] xfs: protect S_DAX transitions in XFS write path
Date: Tue, 26 Sep 2017 09:29:45 +1000 [thread overview]
Message-ID: <20170925232945.GL10955@dastard> (raw)
In-Reply-To: <20170925231404.32723-5-ross.zwisler@linux.intel.com>
On Mon, Sep 25, 2017 at 05:14:01PM -0600, Ross Zwisler wrote:
> In the current XFS write I/O path we check IS_DAX() in
> xfs_file_write_iter() to decide whether to do DAX I/O, direct I/O or
> buffered I/O. This check is done without holding the XFS_IOLOCK, though,
> which means that if we allow S_DAX to be manipulated via the inode flag we
> can run into this race:
>
> CPU 0 CPU 1
> ----- -----
> xfs_file_write_iter()
> IS_DAX() << returns false
> xfs_ioctl_setattr()
> xfs_ioctl_setattr_dax_invalidate()
> xfs_ilock(XFS_MMAPLOCK|XFS_IOLOCK)
> sets S_DAX
> releases XFS_MMAPLOCK and XFS_IOLOCK
> xfs_file_buffered_aio_write()
> does buffered I/O to DAX inode, death
>
> Fix this by ensuring that we only check S_DAX when we hold the XFS_IOLOCK
> in the write path.
NACK. This breaks concurrent direct IO write semantics. We must not
take XFS_IOLOCK_EXCL on direct IO writes unless it is absolutely
necessary - there are lots of applications out there that rely on
these semantics for performance.
CHeers,
Dave.
--
Dave Chinner
david@fromorbit.com
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>,
Jeff Layton <jlayton@poochiereds.net>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 4/7] xfs: protect S_DAX transitions in XFS write path
Date: Tue, 26 Sep 2017 09:29:45 +1000 [thread overview]
Message-ID: <20170925232945.GL10955@dastard> (raw)
In-Reply-To: <20170925231404.32723-5-ross.zwisler@linux.intel.com>
On Mon, Sep 25, 2017 at 05:14:01PM -0600, Ross Zwisler wrote:
> In the current XFS write I/O path we check IS_DAX() in
> xfs_file_write_iter() to decide whether to do DAX I/O, direct I/O or
> buffered I/O. This check is done without holding the XFS_IOLOCK, though,
> which means that if we allow S_DAX to be manipulated via the inode flag we
> can run into this race:
>
> CPU 0 CPU 1
> ----- -----
> xfs_file_write_iter()
> IS_DAX() << returns false
> xfs_ioctl_setattr()
> xfs_ioctl_setattr_dax_invalidate()
> xfs_ilock(XFS_MMAPLOCK|XFS_IOLOCK)
> sets S_DAX
> releases XFS_MMAPLOCK and XFS_IOLOCK
> xfs_file_buffered_aio_write()
> does buffered I/O to DAX inode, death
>
> Fix this by ensuring that we only check S_DAX when we hold the XFS_IOLOCK
> in the write path.
NACK. This breaks concurrent direct IO write semantics. We must not
take XFS_IOLOCK_EXCL on direct IO writes unless it is absolutely
necessary - there are lots of applications out there that rely on
these semantics for performance.
CHeers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
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next prev parent reply other threads:[~2017-09-26 0:05 UTC|newest]
Thread overview: 130+ 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 ` Ross Zwisler
2017-09-25 23:13 ` Ross Zwisler
2017-09-25 23:13 ` [PATCH 1/7] xfs: always use DAX if mount option is used Ross Zwisler
2017-09-25 23:13 ` Ross Zwisler
2017-09-25 23:13 ` Ross Zwisler
2017-09-25 23:38 ` Dave Chinner
2017-09-25 23:38 ` Dave Chinner
2017-09-25 23:38 ` Dave Chinner
2017-09-26 9:35 ` Jan Kara
2017-09-26 9:35 ` Jan Kara
2017-09-26 9:35 ` Jan Kara
2017-09-26 11:09 ` Dave Chinner
2017-09-26 11:09 ` Dave Chinner
2017-09-26 11:09 ` Dave Chinner
2017-09-26 14:37 ` Christoph Hellwig
2017-09-26 14:37 ` Christoph Hellwig
2017-09-26 17:30 ` Ross Zwisler
2017-09-26 17:30 ` Ross Zwisler
2017-09-26 17:30 ` Ross Zwisler
2017-09-26 19:48 ` Darrick J. Wong
2017-09-26 19:48 ` Darrick J. Wong
2017-09-26 22:00 ` Dave Chinner
2017-09-26 22:00 ` Dave Chinner
2017-09-26 22:00 ` Dave Chinner
2017-09-27 6:40 ` Christoph Hellwig
2017-09-27 6:40 ` Christoph Hellwig
2017-09-27 6:40 ` Christoph Hellwig
2017-09-27 16:15 ` Ross Zwisler
2017-09-27 16:15 ` Ross Zwisler
2017-10-01 8:17 ` Christoph Hellwig
2017-10-01 8:17 ` Christoph Hellwig
2017-10-01 8:17 ` Christoph Hellwig
2017-09-26 18:02 ` Eric Sandeen
2017-09-26 18:02 ` Eric Sandeen
2017-09-26 18:02 ` Eric Sandeen
2017-09-26 18:50 ` Ross Zwisler
2017-09-26 18:50 ` Ross Zwisler
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
2017-09-25 23:13 ` Ross Zwisler
2017-09-25 23:13 ` Ross Zwisler
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 17:16 ` Ross Zwisler
2017-09-26 17:16 ` Ross Zwisler
2017-09-26 17:16 ` Ross Zwisler
2017-09-26 17:57 ` Darrick J. Wong
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 23:14 ` Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-25 23:27 ` Dave Chinner
2017-09-25 23:27 ` Dave Chinner
2017-09-25 23:27 ` Dave Chinner
2017-09-26 6:32 ` Christoph Hellwig
2017-09-26 6:32 ` Christoph Hellwig
2017-09-26 6:32 ` Christoph Hellwig
2017-09-26 13:59 ` Dan Williams
2017-09-26 13:59 ` Dan Williams
2017-09-26 13:59 ` Dan Williams
2017-09-26 14:33 ` Christoph Hellwig
2017-09-26 14:33 ` Christoph Hellwig
2017-09-26 14:33 ` Christoph Hellwig
2017-09-26 18:11 ` Dan Williams
2017-09-26 18:11 ` Dan Williams
2017-10-01 8:17 ` Christoph Hellwig
2017-10-01 8:17 ` Christoph Hellwig
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 23:14 ` Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-25 23:29 ` Dave Chinner [this message]
2017-09-25 23:29 ` Dave Chinner
2017-09-25 23:29 ` Dave Chinner
2017-09-25 23:14 ` [PATCH 5/7] xfs: introduce xfs_is_dax_state_changing Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-26 6:33 ` Christoph Hellwig
2017-09-26 6:33 ` Christoph Hellwig
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 23:14 ` Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-25 23:38 ` Dan Williams
2017-09-25 23:38 ` Dan Williams
2017-09-26 18:57 ` Ross Zwisler
2017-09-26 18:57 ` Ross Zwisler
2017-09-26 18:57 ` Ross Zwisler
2017-09-26 19:19 ` Dan Williams
2017-09-26 19:19 ` Dan Williams
2017-09-26 19:19 ` Dan Williams
2017-09-26 21:06 ` Ross Zwisler
2017-09-26 21:06 ` Ross Zwisler
2017-09-26 21:06 ` Ross Zwisler
2017-09-26 21:41 ` Dan Williams
2017-09-26 21:41 ` Dan Williams
2017-09-26 21:41 ` Dan Williams
2017-09-27 11:35 ` Jan Kara
2017-09-27 11:35 ` Jan Kara
2017-09-27 11:35 ` Jan Kara
2017-09-27 14:00 ` Dan Williams
2017-09-27 14:00 ` Dan Williams
2017-09-27 14:00 ` Dan Williams
2017-09-27 15:07 ` Jan Kara
2017-09-27 15:07 ` Jan Kara
2017-09-27 15:07 ` Jan Kara
2017-09-27 15:36 ` Dan Williams
2017-09-27 15:36 ` Dan Williams
2017-09-27 15:39 ` Ross Zwisler
2017-09-27 15:39 ` Ross Zwisler
2017-09-27 15:39 ` Ross Zwisler
2017-09-27 15:54 ` Dan Williams
2017-09-27 15:54 ` Dan Williams
2017-09-27 15:54 ` Dan Williams
2017-09-26 6:34 ` Christoph Hellwig
2017-09-26 6:34 ` Christoph Hellwig
2017-09-26 6:34 ` Christoph Hellwig
2017-09-25 23:14 ` [PATCH 7/7] xfs: re-enable XFS per-inode DAX Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-25 23:14 ` Ross Zwisler
2017-09-26 0:31 ` Dave Chinner
2017-09-26 0:31 ` Dave Chinner
2017-09-26 0:31 ` Dave Chinner
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 6:36 ` Christoph Hellwig
2017-09-26 19:01 ` Ross Zwisler
2017-09-26 19:01 ` Ross Zwisler
2017-09-26 19:01 ` Ross Zwisler
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