Description of problem:

When programed with parted and found below command always return 0
even failed:
# parted /dev/mapper/mpath1 -s -- mklabel msdos mkpart primary 2048s -1s  
device-mapper: remove ioctl failed: Device or resource busy
device-mapper: remove ioctl failed: Device or resource busy
device-mapper: create ioctl failed: Device or resource busy
# echo $?
0  


How reproducible:
  Always as above command.

Steps to Reproduce:
1. Above command.
  
Actual results:


Expected results:
Return no-zero on failed, otherwise return zero.

Additional info:
  Checked source code of parted found in libparted/arch/linux.c, 
  when call dm_ related functions, it always think return value
  <0 if failed, in fact, checked source code of dm_..() functions
  and found it always return 1 on success, error will return 0,
  it's the root cause.

Attach the patch, please review and include it.