[PATCH 1/2] fiemap: add freespace mapping to FS_IOC_FIEMAP

[Mark Tinguely]

On 11/08/12 14:56, Dave Chinner wrote:
> On Thu, Nov 08, 2012 at 10:50:49AM -0600, Mark Tinguely wrote:
>> On 10/18/12 00:11, Dave Chinner wrote:
>>> From: Dave Chinner<dchinner at redhat.com>
>>>
>>> fiemap is used to map extents of used space on files. it's just an
>>> array of extents, though, so there's no reason it can only index
>>> *used*  space.
>>>
>>> Ther eis need for getting freespace layout information into
>>> userspace. For example, defragmentation programs would find it
>>> useful to be able to map the free space in the filesystem to
>>> work out where it is best to move data to defragment it.
>>> Alternatively, knowing where free space is enables us to identify
>>> extents that need to be moved to defragment free space.
>>>
>>> Hence, extend fiemap with the FIEMAP_FLAG_FREESPACE to indicate that
>>> the caller wants to map free space in the range fm_start bytes from
>>> the start of the filesystem for fm_length bytes.
>>>
>>> Because XFS can report extents in size order without needing to
>>> sort, and this information is useful to xfs_fsr, also add
>>> FIEMAP_FLAG_FREESPACE_SIZE to tell the filesystem to return a
>>> freespace map ordered by extent size rather than offset. If there
>>> are multiple extents of the same size, then they are ordered by
>>> offset.
>>>
>>> Signed-off-by: Dave Chinner<dchinner at redhat.com>
>>> ---
>>
>> ...
>>
>>>   --------------
>>> diff --git a/include/linux/fiemap.h b/include/linux/fiemap.h
>>> index d830747..f4fbb9f 100644
>>> --- a/include/linux/fiemap.h
>>> +++ b/include/linux/fiemap.h
>>
>>    include/uabi/linux/fiemap.h
>>            ^^^^
>> other than that, it looks good.
>
> include/uapi/ actaully, but that change was made after I posted the
> patches so there's no surprise that It didn't apply.
>
> As it is, this needs to be redone into an FS_IOC_FIEMAPFS ioctl in
> response to other reviews. I've already done that work (a week ago),
> I just haven't fully tested it yet so I haven't reported it...
>
> Cheers,
>
> Dave.

Okay. Thank-you for the update.

--Mark.