Re: ioctl FIBMAP for dax gone in v4.17-rc1

Dan Williams
2018-04-17T17:05:02Z

On Tue, Apr 17, 2018 at 9:57 AM, Darrick J. Wong
<darrick.wong@oracle.com> wrote:
> On Tue, Apr 17, 2018 at 09:53:47AM -0700, Dan Williams wrote:
>> On Tue, Apr 17, 2018 at 9:10 AM, Christoph Hellwig <hch@infradead.org> wrote:
>> > On Tue, Apr 17, 2018 at 10:40:59PM +0800, Xiong Zhou wrote:
>> >> We got these in v4.17-rc1:
>> >> 6e2608d xfs, dax: introduce xfs_dax_aops
>> >> fb094c9 ext2, dax: introduce ext2_dax_aops
>> >> 5f0663b ext4, dax: introduce ext4_dax_aops
>> >>
>> >> And we don't have ->bmap call in these aops, which may lead
>> >> to the ioctl call failure.
>> >>
>> >> Do we have any plan of adding/supporting it ?
>> >>
>> >> xfstests generic/223 covers this issue. If we are not going
>> >> to support this call for dax, we need to fix the testcase.
>> >
>> > Not supporting ->bmap is a good thing as it is hightly dangerous.
>>
>> I take this to mean "don't fix, it is another casualty of dax being
>> experimental and it won't be coming back". I can get on board with
>> that.
>>
>> Otherwise, I was about to send a series adding bmap to {xfs,ext2,ext4}_dax_ops.
>
> Frankly I'd rather see the swapfile code learn how to iomap and then we
> can get rid of bmap in xfs entirely.

Right, all I am trying to determine is if this is a regression or not.
It seems not supporting bmap on dax going forward is a feature not a
bug.