Description of problem:
It is possible to run thin_rmap without using --region option, but it outputs nothing and the return value is 0. Manpage suggest user must specify region:
"thin_rmap outputs the reverse mapping stored in the metadata on a  device  or  file between a region of thin provisioned pool blocks and the associated thin provisioned devices."
Specifing region correctly prints out the data:
thin_rmap /dev/mapper/vgtest-swapvol --region 0..-1
data 0..3 -> thin(1) 0..3
data 3..19 -> thin(1) 8..24
data 19..20 -> thin(1) 128..129
data 20..21 -> thin(1) 191..192
data 21..24 -> thin(2) 0..3
data 24..40 -> thin(2) 8..24
data 40..41 -> thin(2) 128..129
data 41..42 -> thin(2) 191..192
data 42..45 -> thin(3) 0..3
data 45..61 -> thin(3) 8..24
data 61..62 -> thin(3) 128..129
data 62..63 -> thin(3) 191..192
data 63..66 -> thin(4) 0..3
data 66..82 -> thin(4) 8..24
data 82..83 -> thin(4) 128..129
data 83..84 -> thin(4) 191..192
data 84..87 -> thin(5) 0..3
data 87..103 -> thin(5) 8..24
data 103..104 -> thin(5) 128..129
data 104..105 -> thin(5) 191..192
data 105..108 -> thin(6) 0..3
data 108..124 -> thin(6) 8..24
data 124..125 -> thin(6) 128..129
data 125..126 -> thin(6) 191..192
data 126..129 -> thin(7) 0..3
data 129..145 -> thin(7) 8..24
data 145..146 -> thin(7) 128..129
data 146..147 -> thin(7) 191..192
data 147..150 -> thin(8) 0..3
data 150..166 -> thin(8) 8..24
data 166..167 -> thin(8) 128..129
data 167..168 -> thin(8) 191..192
data 168..171 -> thin(9) 0..3
data 171..187 -> thin(9) 8..24
data 187..188 -> thin(9) 128..129
data 188..189 -> thin(9) 191..192
data 189..192 -> thin(10) 0..3
data 192..208 -> thin(10) 8..24
data 208..209 -> thin(10) 128..129
data 209..210 -> thin(10) 191..192

Version-Release number of selected component (if applicable):
0.7.0-0.1.rc6.el7

How reproducible:
100%

Steps to Reproduce:
1.thin_rmap /dev/mapper/vgtest-swapvol
2.echo $?

Actual results:
Nothing printed and command succeeds
[root@storageqe-18 thin]# thin_rmap /dev/mapper/vgtest-swapvol
[root@storageqe-18 thin]# echo $?
0
 

Expected results:
Either this error or the whole reverse map data
[root@storageqe-18 thin]# thin_rmap /dev/mapper/vgtest-swapvol
No region provided.
Usage: thin_rmap [options] {device|file}
Options:
  {-h|--help}
  {-V|--version}
  {--region <block range>}*
Where:
  <block range> is of the form <begin>..<one-past-the-end>
  for example 5..45 denotes blocks 5 to 44 inclusive, but not block 45


Additional info: