From: Eric Sandeen <sandeen@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH, RFC] xfs: re-enable FIBMAP on reflink; disable for swap
Date: Thu, 30 Aug 2018 11:31:40 -0500 [thread overview]
Message-ID: <dbe27763-2e69-6e3a-f769-2528eda54940@redhat.com> (raw)
In-Reply-To: <20180830162545.GA26816@lst.de>
On 8/30/18 11:25 AM, Christoph Hellwig wrote:
> 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.
>
That's no reason to uniquely disallow it for reflinked files, though;
the problem is universal. It's true for fiemap as well. So I'm not sure
that's an argument against the patch?
-Eric
next prev parent reply other threads:[~2018-08-30 20:34 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
2018-08-30 16:31 ` Eric Sandeen [this message]
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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