nova volume-attach : Misleading error statement while attaching new volume to already existing device name.

[Roshan R Anvekar]

Description:
1. Create a volume A and attach to VM as device: /dev/vdc
2. Create another volume B and attach to VM as device: /dev/vdc

Expected: The error statement should be that "/dev/vdc is already inuse" for the VM.
Observation: Following error statement is issued:
ubuntu@devstack-12:~/workspace$ nova volume-attach 504d4c91-ce15-4af2-a7b4-4b81d55d8066 84a05d96-734d-417b-bf31-11e2fbcb86ae /dev/vdc
ERROR: The supplied device path (/dev/vda) is in use. (HTTP 400) (Request-ID: req-cd9f7e3b-51be-4358-a2d2-bf01e40931d9)

The command execution stream:
ubuntu@devstack-12:~/workspace$ nova volume-list
+--------------------------------------+-----------+--------------+------+-------------+--------------------------------------+
| ID | Status | Display Name | Size | Volume Type | Attached to |
+--------------------------------------+-----------+--------------+------+-------------+--------------------------------------+
| 6dce0d3f-dcb5-4827-81a8-91bcb335e677 | in-use | None | 1 | None | 504d4c91-ce15-4af2-a7b4-4b81d55d8066 |
| 84a05d96-734d-417b-bf31-11e2fbcb86ae | available | None | 2 | None | |
+--------------------------------------+-----------+--------------+------+-------------+--------------------------------------+
ubuntu@devstack-12:~/workspace$ nova list
+--------------------------------------+--------+--------+--------------------------------+
| ID | Name | Status | Networks |
+--------------------------------------+--------+--------+--------------------------------+
| 504d4c91-ce15-4af2-a7b4-4b81d55d8066 | test02 | ACTIVE | private=10.0.0.3, 172.24.4.225 |
| b0626426-3f51-499e-aefc-baf92ae9223b | test3 | ACTIVE | private=10.0.0.2 |
+--------------------------------------+--------+--------+--------------------------------+
ubuntu@devstack-12:~/workspace$ nova volume-attach 504d4c91-ce15-4af2-a7b4-4b81d55d8066 84a05d96-734d-417b-bf31-11e2fbcb86ae /dev/vdc
ERROR: The supplied device path (/dev/vda) is in use. (HTTP 400) (Request-ID: req-cd9f7e3b-51be-4358-a2d2-bf01e40931d9)
ubuntu@devstack-12:~/workspace$ nova volume-attach 504d4c91-ce15-4af2-a7b4-4b81d55d8066 84a05d96-734d-417b-bf31-11e2fbcb86ae /dev/vdd
+----------+--------------------------------------+
| Property | Value |
+----------+--------------------------------------+
| device | /dev/vdd |
| serverId | 504d4c91-ce15-4af2-a7b4-4b81d55d8066 |
| id | 84a05d96-734d-417b-bf31-11e2fbcb86ae |
| volumeId | 84a05d96-734d-417b-bf31-11e2fbcb86ae |
+----------+--------------------------------------+
ubuntu@devstack-12:~/workspace$ nova volume-show 6dce0d3f-dcb5-4827-81a8-91bcb335e677
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Property | Value |
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| status | in-use |
| display_name | None |
| attachments | [{u'device': u'/dev/vdc', u'server_id': u'504d4c91-ce15-4af2-a7b4-4b81d55d8066', u'id': u'6dce0d3f-dcb5-4827-81a8-91bcb335e677', u'volume_id': u'6dce0d3f-dcb5-4827-81a8-91bcb335e677'}] |
| availability_zone | nova |
| bootable | false |
| created_at | 2013-02-04T07:27:14.000000 |
| display_description | None |
| volume_type | None |
| snapshot_id | None |
| source_volid | None |
| size | 1 |
| id | 6dce0d3f-dcb5-4827-81a8-91bcb335e677 |
| metadata | {} |
+---------------------+--------------------------------------------------------- --------------------+
ubuntu@devstack-12:~/workspace$ !ssh
ssh -i openkey.pem cirros@172.24.4.225
$ sudo fdisk -l

Disk /dev/vda: 25 MB, 25165824 bytes
16 heads, 63 sectors/track, 48 cylinders, total 49152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/vda doesn't contain a valid partition table

Disk /dev/vdb: 1073 MB, 1073741824 bytes
16 heads, 63 sectors/track, 2080 cylinders, total 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/vdb doesn't contain a valid partition table

Disk /dev/vdc: 2147 MB, 2147483648 bytes
16 heads, 63 sectors/track, 4161 cylinders, total 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/vdc doesn't contain a valid partition table
$

VM type: m1.tiny -- which shows minimal 25MB root partition.
Seems like VM is skipping considering the root partition as device.

[Roshan R Anvekar (roshan-anvekar)]

With reference to command execution:
ubuntu@devstack-12:~/workspace$ nova volume-attach 504d4c91-ce15-4af2-a7b4-4b81d55d8066 84a05d96-734d-417b-bf31-11e2fbcb86ae /dev/vdc
ERROR: The supplied device path (/dev/vda) is in use. (HTTP 400) (Request-ID: req-cd9f7e3b-51be-4358-a2d2-bf01e40931d9)

>> I would expect the command to say : " The supplied device path (/dev/vdb) is in use."
But it is pointing out to the wrong device altogether : /dev/vda ( With my assumption that vda is root partition and vdb is attached partition )
Even if internally the VM uses different device name, I would expect it to point to attached volume in error statement rather then to root partition. So I see a mapping error here which I guess is different from the Duplicate bug mentioned.