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From: Greg KH <greg@kroah.com>
To: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org, linux-xfs@vger.kernel.org,
	"Darrick J . Wong" <darrick.wong@oracle.com>
Subject: Re: [PATCH 12/26] xfs: reject all unaligned direct writes to reflinked files
Date: Sat, 1 Apr 2017 19:26:03 +0200	[thread overview]
Message-ID: <20170401172603.GA5701@kroah.com> (raw)
In-Reply-To: <20170401172108.GA10203@kroah.com>

On Sat, Apr 01, 2017 at 07:21:08PM +0200, Greg KH wrote:
> On Sat, Apr 01, 2017 at 08:34:58AM +0200, Christoph Hellwig wrote:
> > commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream.
> > 
> > We currently fall back from direct to buffered writes if we detect a
> > remaining shared extent in the iomap_begin callback.  But by the time
> > iomap_begin is called for the potentially unaligned end block we might
> > have already written most of the data to disk, which we'd now write
> > again using buffered I/O.  To avoid this reject all writes to reflinked
> > files before starting I/O so that we are guaranteed to only write the
> > data once.
> > 
> > The alternative would be to unshare the unaligned start and/or end block
> > before doing the I/O. I think that's doable, and will actually be
> > required to support reflinks on DAX file system.  But it will take a
> > little more time and I'd rather get rid of the double write ASAP.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > Reviewed-by: Brian Foster <bfoster@redhat.com>
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Any specific reason you don't want this one in 4.9 as well?

Nevermind, it's there, missed it, my fault...

greg k-h

  parent reply	other threads:[~2017-04-01 17:26 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-01  6:34 4.10-stable updates for XFS Christoph Hellwig
2017-04-01  6:34 ` [PATCH 01/26] xfs: pull up iolock from xfs_free_eofblocks() Christoph Hellwig
2017-04-01  6:34 ` [PATCH 02/26] xfs: sync eofblocks scans under iolock are livelock prone Christoph Hellwig
2017-04-01  6:34 ` [PATCH 03/26] xfs: fix eofblocks race with file extending async dio writes Christoph Hellwig
2017-04-01  6:34 ` [PATCH 04/26] xfs: fix toctou race when locking an inode to access the data map Christoph Hellwig
2017-04-01  6:34 ` [PATCH 05/26] xfs: fail _dir_open when readahead fails Christoph Hellwig
2017-04-01  6:34 ` [PATCH 06/26] xfs: filter out obviously bad btree pointers Christoph Hellwig
2017-04-01  6:34 ` [PATCH 07/26] xfs: check for obviously bad level values in the bmbt root Christoph Hellwig
2017-04-01  6:34 ` [PATCH 08/26] xfs: verify free block header fields Christoph Hellwig
2017-04-01  6:34 ` [PATCH 09/26] xfs: allow unwritten extents in the CoW fork Christoph Hellwig
2017-04-01  6:34 ` [PATCH 10/26] xfs: mark speculative prealloc CoW fork extents unwritten Christoph Hellwig
2017-04-01  6:34 ` [PATCH 11/26] xfs: reset b_first_retry_time when clear the retry status of xfs_buf_t Christoph Hellwig
2017-04-01  6:34 ` [PATCH 12/26] xfs: reject all unaligned direct writes to reflinked files Christoph Hellwig
2017-04-01 17:21   ` Greg KH
2017-04-01 17:22     ` Christoph Hellwig
2017-04-01 17:26     ` Greg KH [this message]
2017-04-01 17:42       ` Christoph Hellwig
2017-04-01  6:34 ` [PATCH 13/26] xfs: update ctime and mtime on clone destinatation inodes Christoph Hellwig
2017-04-01  6:35 ` [PATCH 14/26] xfs: correct null checks and error processing in xfs_initialize_perag Christoph Hellwig
2017-04-01  6:35 ` [PATCH 15/26] xfs: don't fail xfs_extent_busy allocation Christoph Hellwig
2017-04-01  6:35 ` [PATCH 16/26] xfs: handle indlen shortage on delalloc extent merge Christoph Hellwig
2017-04-01  6:35 ` [PATCH 17/26] xfs: split indlen reservations fairly when under reserved Christoph Hellwig
2017-04-01  6:35 ` [PATCH 18/26] xfs: fix uninitialized variable in _reflink_convert_cow Christoph Hellwig
2017-04-01  6:35 ` [PATCH 19/26] xfs: don't reserve blocks for right shift transactions Christoph Hellwig
2017-04-01  6:35 ` [PATCH 20/26] xfs: Use xfs_icluster_size_fsb() to calculate inode chunk alignment Christoph Hellwig
2017-04-01  6:35 ` [PATCH 21/26] xfs: tune down agno asserts in the bmap code Christoph Hellwig
2017-04-01  6:35 ` [PATCH 22/26] xfs: only reclaim unwritten COW extents periodically Christoph Hellwig
2017-04-01  6:35 ` [PATCH 23/26] xfs: fix and streamline error handling in xfs_end_io Christoph Hellwig
2017-04-01  6:35 ` [PATCH 24/26] xfs: Use xfs_icluster_size_fsb() to calculate inode alignment mask Christoph Hellwig
2017-04-01  6:35 ` [PATCH 25/26] xfs: use iomap new flag for newly allocated delalloc blocks Christoph Hellwig
2017-04-01  6:35 ` [PATCH 26/26] xfs: try any AG when allocating the first btree block when reflinking Christoph Hellwig
2017-04-01  7:43 ` 4.10-stable updates for XFS Eryu Guan
2017-04-01 13:37   ` Christoph Hellwig
2017-04-01 17:32 ` Greg KH
  -- strict thread matches above, loose matches on Subject: below --
2017-03-27  8:38 Christoph Hellwig
2017-03-27  8:38 ` [PATCH 12/26] xfs: reject all unaligned direct writes to reflinked files Christoph Hellwig

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