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From: Christoph Hellwig <hch@lst.de>
To: Eric Sandeen <sandeen@redhat.com>
Cc: linux-xfs <linux-xfs@vger.kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH, RFC] xfs: re-enable FIBMAP on reflink; disable for swap
Date: Thu, 30 Aug 2018 18:25:45 +0200	[thread overview]
Message-ID: <20180830162545.GA26816@lst.de> (raw)
In-Reply-To: <2eb759e5-2faa-67fd-5c16-c1d8edc42d02@redhat.com>

On Thu, Aug 30, 2018 at 11:10:05AM -0500, Eric Sandeen wrote:
> We disabled FIBMAP/bmap calls for reflinked files because swap will then
> writes directly to the blocks, bypassing COW mechanisms, and breaking
> copy on write.  As noted in commit db1327b, this restriction also breaks
> bootloaders that want to use the FIBMAP ioctl.
> 
> Rather than disabling the entire mapping interface for everyone just
> because swapon may abuse the info, teach xfs_iomap_swapfile_activate()
> to reject activation for reflinked files, and re-enable the FIBMAP
> interface.

Every use of the feature is an abuse, and that includes bootloaders.
By the time you've obtained the information it can (and often will)
be stale.

  reply	other threads:[~2018-08-30 20:25 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-30 16:10 [PATCH, RFC] xfs: re-enable FIBMAP on reflink; disable for swap Eric Sandeen
2018-08-30 16:25 ` Christoph Hellwig [this message]
2018-08-30 16:31   ` Eric Sandeen
2018-08-30 16:36     ` Christoph Hellwig
2018-08-30 16:35       ` Eric Sandeen
2018-08-30 18:02         ` Brian Foster
2018-08-30 18:28           ` Darrick J. Wong
2018-08-30 18:51             ` Eric Sandeen
2018-08-30 19:39               ` Brian Foster
2018-08-30 19:47                 ` Eric Sandeen
2018-08-30 19:58                   ` Brian Foster
2018-08-31  0:11               ` Dave Chinner
2018-08-31  1:34                 ` Eric Sandeen
2018-08-31  3:05                   ` Dave Chinner
2018-08-31 13:08                     ` Eric Sandeen
2018-09-01  8:32                       ` Christoph Hellwig
2018-08-31  6:28             ` Christoph Hellwig
2018-08-31 12:36               ` Brian Foster
2018-09-01  8:31                 ` Christoph Hellwig
2018-09-02 14:08                 ` Carlos Maiolino
2018-09-02 17:52                   ` Eric Sandeen
2018-09-03 10:21                     ` Carlos Maiolino

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