Steps to reproduce

utility_container:

# for i in {1..5}; do cinder create --display-name test$i 1; done

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable | Attached to |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
| 165e09a7-7e2c-42ad-8cd8-e01ecaa6a8b6 | available |    test3     |  1   |     None    |  false   |             |
| 77bce6ce-70c5-4109-9133-31c7898e511f | available |    test1     |  1   |     None    |  false   |             |
| 8bc99d61-068c-4dcd-bb14-28561b76e333 | available |    test4     |  1   |     None    |  false   |             |
| f4551c7f-6d0b-4b56-afdf-4d67d4e07977 | available |    test5     |  1   |     None    |  false   |             |
| fade96b4-eb74-4ae2-bd64-8bc761cb4eee | available |    test2     |  1   |     None    |  false   |             |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+

# cinder delete test3

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable | Attached to |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
| 77bce6ce-70c5-4109-9133-31c7898e511f | available |    test1     |  1   |     None    |  false   |             |
| 8bc99d61-068c-4dcd-bb14-28561b76e333 | available |    test4     |  1   |     None    |  false   |             |
| f4551c7f-6d0b-4b56-afdf-4d67d4e07977 | available |    test5     |  1   |     None    |  false   |             |
| fade96b4-eb74-4ae2-bd64-8bc761cb4eee | available |    test2     |  1   |     None    |  false   |             |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+

# cinder create --display-name test6 1

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable | Attached to |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+
| 77bce6ce-70c5-4109-9133-31c7898e511f | available |    test1     |  1   |     None    |  false   |             |
| 7e15a9b5-c002-4c3c-8eb5-298e4a91b90c | available |    test6     |  1   |     None    |  false   |             |
| 8bc99d61-068c-4dcd-bb14-28561b76e333 | available |    test4     |  1   |     None    |  false   |             |
| f4551c7f-6d0b-4b56-afdf-4d67d4e07977 | available |    test5     |  1   |     None    |  false   |             |
| fade96b4-eb74-4ae2-bd64-8bc761cb4eee | available |    test2     |  1   |     None    |  false   |             |
+--------------------------------------+-----------+--------------+------+-------------+----------+-------------+


volumes_container:

# ls -l /dev/mapper
total 0
brw-rw---- 1 root disk 252,   0 Jun  5 16:43 cinder--volumes-volume--77bce6ce--70c5--4109--9133--31c7898e511f
brw-rw---- 1 root disk 252,   2 Jun  5 16:45 cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c
brw-rw---- 1 root disk 252,   3 Jun  5 16:43 cinder--volumes-volume--8bc99d61--068c--4dcd--bb14--28561b76e333
brw-rw---- 1 root disk 252,   4 Jun  5 16:43 cinder--volumes-volume--f4551c7f--6d0b--4b56--afdf--4d67d4e07977
brw-rw---- 1 root disk 252,   1 Jun  5 16:43 cinder--volumes-volume--fade96b4--eb74--4ae2--bd64--8bc761cb4eee
crw------- 1 root root  10, 236 Jun  5 16:00 control

# dmsetup info -c -o name,major,minor
Name                                                             Maj Min
cinder--volumes-volume--8bc99d61--068c--4dcd--bb14--28561b76e333 252   3
cinder--volumes-volume--f4551c7f--6d0b--4b56--afdf--4d67d4e07977 252   4
cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c 252   2
cinder--volumes-volume--fade96b4--eb74--4ae2--bd64--8bc761cb4eee 252   1
cinder--volumes-volume--77bce6ce--70c5--4109--9133--31c7898e511f 252   0


volumes_host:

# reboot


volumes_container:

# ls -l /dev/mapper
total 0
brw-rw---- 1 root disk 252,   0 Jun  5 16:43 cinder--volumes-volume--77bce6ce--70c5--4109--9133--31c7898e511f
brw-rw---- 1 root disk 252,   2 Jun  5 16:45 cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c
brw-rw---- 1 root disk 252,   3 Jun  5 16:43 cinder--volumes-volume--8bc99d61--068c--4dcd--bb14--28561b76e333
brw-rw---- 1 root disk 252,   4 Jun  5 16:43 cinder--volumes-volume--f4551c7f--6d0b--4b56--afdf--4d67d4e07977
brw-rw---- 1 root disk 252,   1 Jun  5 16:43 cinder--volumes-volume--fade96b4--eb74--4ae2--bd64--8bc761cb4eee
crw------- 1 root root  10, 236 Jun  5 16:00 control

# dmsetup info -c -o name,major,minor
Name                                                             Maj Min
cinder--volumes-volume--8bc99d61--068c--4dcd--bb14--28561b76e333 252   2
cinder--volumes-volume--f4551c7f--6d0b--4b56--afdf--4d67d4e07977 252   3
cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c 252   4
cinder--volumes-volume--fade96b4--eb74--4ae2--bd64--8bc761cb4eee 252   1
cinder--volumes-volume--77bce6ce--70c5--4109--9133--31c7898e511f 252   0



7e15a9b5-c002-4c3c-8eb5-298e4a91b90c is the volume test6. The next two commands pull it out from the output of the above two commands. Notice that for /dev/mapper the minor device number is 2 whereas dmsetup info lists it as 4.

# ls -l /dev/mapper | grep 7e15a9b5
brw-rw---- 1 root disk 252,   2 Jun  5 16:45 cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c

# dmsetup info -c -o name,major,minor | grep 7e15a9b5
cinder--volumes-volume--7e15a9b5--c002--4c3c--8eb5--298e4a91b90c 252   4