XFS_IOC_FSEMAP requirements

[Carlos Maiolino <cmaiolino@redhat.com>]

Hi folks,

I've been working on the implementation of FSEMAP ioctl as we've been discussed
previously, and, the first discussion about this, was about using the same
fiemap structures to retrieve free extents from the btrees.

By our last chat about it (it's been a while, I know, I got busy with more
important stuff :), Dave suggested another uses for FSEMAP that were not in my
mind, so, I think it deserves its own implementation, independent of fiemap from
where the same idea came from.

So, I'd like to know, what else might FSEMAP be used for, beyond iterating free
space extents, so I can think of a new struct to be exchanged between user<->
kernel. FSEMAP is supposed to complement GETFSMAPX, discussed in LSF this year,
but I don't know if is there any plan to keep with GETFSMAPX or not, or even if
FSEMAP is still a valuable idea :)

Any comments, suggestions about to what direction should FSEMAP go?

Cheers
-- 
Carlos