Split fhandler_disk_file::fallocate into multiple methods, each
implementing a different aspect of fallocate(2), thus adding
FALLOC_FL_PUNCH_HOLE and FALLOC_FL_ZERO_RANGE handling.
For more correctly implementing posix_fallocate(3) semantics, make
sure to re-allocate holes in the given range if the file is sparse.
While at it, change the way checking when to make a file sparse.
The rule is now, make file sparse if the hole created by the action
spans at least one sparse block, taking the allocation granularity
of sparse files into account.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
65831f88d6