bug#20826: SEEK_HOLE not supported for ext4 for kernel < 3.1

[Johannes Meixner]

An addendum FYI:

From our (SUSE) kernel developers I got the information that

only ext4 has this problem and that kernel git commit c334b1138bd4
(handle SEEK_HOLE/SEEK_DATA generically in /fs/ext4/file.c)
fixes it.