[LTP] [PATCH 1/1] Use real FS block size in fallocate05

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> I think it might be better to change the test scenario a bit:
> 1. fallocate(FALLOCATE_BLOCKS * blocksize)
> 2. tst_fill_fs()
> 3. write(FALLOCATE_BLOCKS * blocksize)
> 4. repeat fallocate(blocksize) until we get ENOSPC
> 5. write() into all blocks allocated in step 4
> 6. check that another write() will get ENOSPC
> 7. test fallocate(PUNCH_HOLE | KEEP_SIZE)
> 
> This should get us around the issue with tst_fill_fs() and still
> properly validate that fallocate() handles full FS gracefully.

Looping over the second fallocate until we got ENOSPC sounds reasonable
to me.

> The only remaining issue is whether it's correct for Btrfs to only
> release blocks when you deallocate the whole file. I still haven't heard
> back from our Btrfs dev.

So the punched hole does not free space on Btrfs even if we are FS block
aligned? I was under an impression that it should, but again Btrfs is
copy-on-write filesystem, so it may want to keep a copy of the discarded
blocks anyways.

-- 
Cyril Hrubis
chrubis@suse.cz