On Fri, Mar 04, 2016 at 07:13:25PM -0800, Linus Torvalds wrote:

quoted

+       /* We can't change the bdev size from here */
+       if (!(mode & FALLOC_FL_KEEP_SIZE))
+               return -EOPNOTSUPP;

Oh, and this I think is wrong.

The thing is, FALLOC_FL_KEEP_SIZE is only supposed to matter if the
region is outside the existing length.

For allocations...

So if y ou punch a hole in the middle of a file, you don't need
FALLOC_FL_KEEP_SIZE.

For FALLOC_FL_PUNCH_HOLE we always require FALLOC_FL_KEEP_SIZE so far,
and I'd rather not change things for block devices just because we can.