punch command works incorrect in debugfs

[Zheng Liu <gnehzuil.liu@gmail.com>]

Hi all,

I found a bug in debugfs that 'punch' command work incorrect for a
indirect-based file.  The bug can be triggered by the following
commands, and it seems that the problem is in libext2fs library.  I
file this bug in mailing list because I have no time to look at it
carefully and I doubt that this command is not used frequently.

[reproduce steps]
  sudo mkfs.ext4 -O ^extent ${DEV}
  sudo mount -t ext4 ${DEV} ${MNT}
  sudo dd if=/dev/zero of=${MNT}/punch-file bs=4k count=16
  sync
  sudo umount ${MNT}
  sudo debugfs ${DEV} -R 'stat punch-file'
  sudo debugfs -w ${DEV} -R 'punch punch-file 4 6'
  sudo debugfs ${DEV} -R 'stat punch-file'

[expected result]
...
BLOCKS:
(0-3):34304-34307, (6-11):34310-34315, (IND):33793, (12-15):34316-34319
...

[wrong result]
...
BLOCKS:
(0-11):34304-34315, (IND):33793, (12-15):34316-34319
...

Regards,
                                                - Zheng