This function is very similar to find_first_extent_bit except that it
locates the first contiguous span of space which does not have bits set.
It's intended use is in the freespace trimming code.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>