Re: [Nbd] TRIM stuff

[Folkert van Heusden <folkert@...421...>]

>> > So yesterday I implemented the fallocate(FALLOC_FL_PUNCH_HOLE) stuff for
>> > NBD_CMD_TRIM. It's compile-tested, but not yet functionally tested. To
>> > be honest, I'm not entirely sure how to test whether a file is sparse in
>> > a particular region; anyone?
>>
>> I think you can use debugfs's dump_extents command (from memory).
>
> Yes, but that requires an unmounted filesystem. If I want to add this to
> the test suite, that's not going to work.

Maybe the FIBMAP/FIEMAP ioctls can help you.
See http://www.mirrorservice.org/sites/dl.sourceforge.net/pub/sourceforge/g/project/gu/gujin/gujin/2.8.1/gujin-2.8.1.tar.gz/gujin/showmap.c?extract=true
for an example.