Sheepdog driver doesn't set size correctly on create from snapshot

[ustcdylan]

My openstack version: stable/icehouse and I use sheepdog as the cinder's backend storage, and use "cinder create" to create a new volume based a snapshot with a given size, we find the size it not work. Other backend storages have no problem, for example lvm.

You can reproduce this bug as follows:
[root@compute-63-10 ~]# cinder snapshot-list
+--------------------------------------+--------------------------------------+-----------+------------------------------------------+------+
| ID | Volume ID | Status | Display Name | Size |
+--------------------------------------+--------------------------------------+-----------+------------------------------------------+------+
| e6a25098-faa3-4326-860d-8ce386a32d9d | ac8cccb7-fc98-4c75-9f00-492a61a59e27 | available | CentOS 6.5 64bit (EBS) | 10 |
+--------------------------------------+--------------------------------------+-----------+------------------------------------------+------+

[root@compute-63-10 ~]# cinder create --snapshot-id e6a25098-faa3-4326-860d-8ce386a32d9d --display-name dylan 40
+---------------------+--------------------------------------+
| Property | Value |
+---------------------+--------------------------------------+
| attachments | [] |
| availability_zone | nova |
| bootable | false |
| created_at | 2014-12-05T09:55:42.892741 |
| display_description | None |
| display_name | dylan |
| encrypted | False |
| id | 2cc9dd67-951a-46c0-b2ad-2c2534c358eb |
| metadata | {} |
| size | 40 |
| snapshot_id | e6a25098-faa3-4326-860d-8ce386a32d9d |
| source_volid | None |
| status | creating |
| volume_type | ebs |
+---------------------+--------------------------------------+

we check the volume size in the compute node which it attached to or if the new volume has a guest os, we can login in and check the disk size by "fdisk -l"

[root@compute-63-06 by-path]# qemu-img info ip-192.168.33.136\:3260-iscsi-iqn.2014-05.cmcc.bigcloud\:volume-07f1e3fb-78ae-46d5-8ac5-a9c888e55b72-lun-1
image: ip-192.168.33.136:3260-iscsi-iqn.2014-05.cmcc.bigcloud:volume-07f1e3fb-78ae-46d5-8ac5-a9c888e55b72-lun-1
file format: raw
virtual size: 10G (10737418240 bytes)
disk size: 0

[ustcdylan (ustcdylan)]

I give a patch here:https://review.openstack.org/#/c/139804/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/139804
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=337342d0894df0661810b8f9b08d26611ad43962
Submitter: Jenkins
Branch: master

commit 337342d0894df0661810b8f9b08d26611ad43962
Author: ustcdylan <email address hidden>
Date: Sat Dec 6 22:23:21 2014 +0800

    Fix bug in sheepdog driver: the wrong volume size

    We give a volume size when create a volume from an snapshot,
    but the sheepdog driver ignores the size.

    Change-Id: I4310e7ef07e98c002ad3494e623ea243e3aad468
    Closes-Bug: #1399598