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.
next prev parent 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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