volume size is smaller than the cache size

Image info:
[stack@localhost devstack]$ glance image-show 270c0ea5-76bc-4b3b-8293-b3562d7a85b5
+------------------+----------------------------------------------------------------------------------+
| Property | Value |
+------------------+----------------------------------------------------------------------------------+
| checksum | 056fcc63eb0e7aa3fc36c2d384e1a45d |
| container_format | bare |
| created_at | 2019-09-13T00:32:27Z |
| disk_format | qcow2 |
| id | 270c0ea5-76bc-4b3b-8293-b3562d7a85b5 |
| min_disk | 0 |
| min_ram | 0 |
| name | CentOS7-1611 |
| os_hash_algo | sha512 |
| os_hash_value | fa5515da171d31580ed3900036676c85345557bfd0bf8076ec4e0e304306422fcbe7ea4b330375cf |
| | 4850887507e01a95b98b257b0464a8baffc5b55114b7084a |
| os_hidden | False |
| owner | d01ec9caf63a4211a7ab47bea3e489e7 |
| protected | False |
| size | 1317994496 |
| status | active |
| tags | [] |
| updated_at | 2019-09-13T00:33:12Z |
| virtual_size | Not available |
| visibility | shared |
+------------------+----------------------------------------------------------------------------------+
[stack@localhost devstack]$ qemu-img info 270c0ea5-76bc-4b3b-8293-b3562d7a85b5
image: 270c0ea5-76bc-4b3b-8293-b3562d7a85b5
file format: qcow2
virtual size: 8.0G (8589934592 bytes)
disk size: 1.2G
cluster_size: 65536
Format specific information:
    compat: 0.10
    refcount bits: 16
[stack@localhost devstack]$

Create a 9GB volume, auto creating a 8GB image cache volume: This is right.
[stack@localhost devstack]$ cinder list --all | grep available
| 59959108-bde2-4477-b6ea-cededdbdb8f7 | d01ec9caf63a4211a7ab47bea3e489e7 | available | - | 9 | yenai-lvm | true | |
| ea5d357c-10a3-46c5-aee6-7e2281717f62 | 4568925a214e48d4ab32bcd71c6faff1 | available | image-270c0ea5-76bc-4b3b-8293-b3562d7a85b5 | 8 | yenai-lvm | false | |
[stack@localhost devstack]$

Create a 1GB volume: Failed(size is not fit). This is right.
[stack@localhost devstack]$ cinder create --image-id 270c0ea5-76bc-4b3b-8293-b3562d7a85b5 --volume-type yenai-lvm 1
ERROR: Invalid input received: Size of specified image 2GB is larger than volume size 1GB. (HTTP 400) (Request-ID: req-a1fddaa0-4f31-46ce-a5a1-4c7da3c0b18c)

★★★★★ Create a 2GB volume: success!!! This is a big problem.
[stack@localhost devstack]$ cinder create --image-id 270c0ea5-76bc-4b3b-8293-b3562d7a85b5 --volume-type yenai-lvm 2
+--------------------------------+--------------------------------------+
| Property | Value |
+--------------------------------+--------------------------------------+
| attachments | [] |
| availability_zone | nova |
| bootable | false |
| consistencygroup_id | None |
| created_at | 2019-09-13T02:28:27.000000 |
| description | None |
| encrypted | False |
| id | 48ad9897-5349-4cf8-b393-a8043d2f437b |
| metadata | {} |
| migration_status | None |
| multiattach | False |
| name | None |
| os-vol-host-attr:host | None |
| os-vol-mig-status-attr:migstat | None |
| os-vol-mig-status-attr:name_id | None |
| os-vol-tenant-attr:tenant_id | d01ec9caf63a4211a7ab47bea3e489e7 |
| replication_status | None |
| size | 2 |
| snapshot_id | None |
| source_volid | None |
| status | creating |
| updated_at | None |
| user_id | 83aa2159496d4a20bc83185a56021ef8 |
| volume_type | yenai-lvm |
+--------------------------------+--------------------------------------+
[stack@localhost devstack]$ cinder list --all
+--------------------------------------+----------------------------------+-----------+--------------------------------------------+------+----------------------+----------+--------------------------------------+
| ID | Tenant ID | Status | Name | Size | Volume Type | Bootable | Attached to |
+--------------------------------------+----------------------------------+-----------+--------------------------------------------+------+----------------------+----------+--------------------------------------+
| 48ad9897-5349-4cf8-b393-a8043d2f437b | d01ec9caf63a4211a7ab47bea3e489e7 | available | - | 2 | yenai-lvm | true | |
| ea5d357c-10a3-46c5-aee6-7e2281717f62 | 4568925a214e48d4ab32bcd71c6faff1 | available | image-270c0ea5-76bc-4b3b-8293-b3562d7a85b5 | 8 | yenai-lvm | false | |
+--------------------------------------+----------------------------------+-----------+--------------------------------------------+------+----------------------+----------+--------------------------------------+

LVM info:
[stack@localhost devstack]$ sudo lvs
  LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
  root cl -wi-ao---- <35.00g
  swap cl -wi-ao---- 4.00g
  stack-volumes-lvmdriver-1-pool stack-volumes-lvmdriver-1 twi-aotz-- 22.80g 0.00 10.50
  _snapshot-5f9d0432-5251-407a-959c-53be0c6505db yenai_vg Vwi-a-tz-k 1.00g yenai_vg-pool volume-d3c610b8-615b-4f42-bc9d-2d4d1fd663df 8.87
  volume-48ad9897-5349-4cf8-b393-a8043d2f437b yenai_vg Vwi-a-tz-- 8.00g yenai_vg-pool volume-ea5d357c-10a3-46c5-aee6-7e2281717f62 100.00
  volume-ea5d357c-10a3-46c5-aee6-7e2281717f62 yenai_vg Vwi-a-tz-- 8.00g yenai_vg-pool 100.00
  yenai_vg-pool yenai_vg twi-aotz-- 190.00g 4.26 12.62
[stack@localhost devstack]$

Just see the log, whitout any size check:
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.image.cache [None req-e3bccb29-dbef-4500-b060-5e82ab7d1bbf None None] Found image-volume cache entry: {'last_used':
datetime.datetime(2019, 9, 13, 2, 28, 27, 750938), 'image_updated_at': datetime.datetime(2019, 9, 13, 0, 33, 12), 'image_id': u'270c0ea5-76bc-4b3b-8293-b3562d7a85b5', 'host': u'localhost.loc
aldomain@yenai-lvm#yenai-lvm', 'volume_id': u'ea5d357c-10a3-46c5-aee6-7e2281717f62', 'id': 7, 'size': 8}. {{(pid=120585) get_entry /opt/stack/cinder/cinder/image/cache.py:65}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.image.cache [None req-e3bccb29-dbef-4500-b060-5e82ab7d1bbf None None] Image-volume cache entry image_update_at = 201
9-09-13 00:33:12+00:00, requested image updated_at = 2019-09-13 00:33:12+00:00. {{(pid=120585) _should_update_entry /opt/stack/cinder/cinder/image/cache.py:227}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.volume.flows.manager.create_volume [None req-e3bccb29-dbef-4500-b060-5e82ab7d1bbf None None] Found cache entry for i
mage = 270c0ea5-76bc-4b3b-8293-b3562d7a85b5 on host localhost.localdomain@yenai-lvm#yenai-lvm. {{(pid=120585) _prepare_image_cache_entry /opt/stack/cinder/cinder/volume/flows/manager/create_
volume.py:647}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.coordination [None req-e3bccb29-dbef-4500-b060-5e82ab7d1bbf None None] Lock "cinder-270c0ea5-76bc-4b3b-8293-b3562d7a
85b5" released by "_prepare_image_cache_entry" :: held 0.010s {{(pid=120585) _synchronized /opt/stack/cinder/cinder/coordination.py:162}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.volume.flows.manager.create_volume [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Attempting to retrieve
cache entry for image = 270c0ea5-76bc-4b3b-8293-b3562d7a85b5 on host localhost.localdomain@yenai-lvm#yenai-lvm. {{(pid=120585) _create_from_image_cache /opt/stack/cinder/cinder/volume/flows/
manager/create_volume.py:602}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.image.cache [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Found image-volume cache entry: {'last_used':
datetime.datetime(2019, 9, 13, 2, 28, 27, 760700), 'image_updated_at': datetime.datetime(2019, 9, 13, 0, 33, 12), 'image_id': u'270c0ea5-76bc-4b3b-8293-b3562d7a85b5', 'host': u'localhost.loc
aldomain@yenai-lvm#yenai-lvm', 'volume_id': u'ea5d357c-10a3-46c5-aee6-7e2281717f62', 'id': 7, 'size': 8}. {{(pid=120585) get_entry /opt/stack/cinder/cinder/image/cache.py:65}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.image.cache [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Image-volume cache entry image_update_at = 201
9-09-13 00:33:12+00:00, requested image updated_at = 2019-09-13 00:33:12+00:00. {{(pid=120585) _should_update_entry /opt/stack/cinder/cinder/image/cache.py:227}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG cinder.volume.flows.manager.create_volume [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Creating from source im
age-volume ea5d357c-10a3-46c5-aee6-7e2281717f62 {{(pid=120585) _create_from_image_cache /opt/stack/cinder/cinder/volume/flows/manager/create_volume.py:615}}
Sep 13 10:28:27 localhost.localdomain cinder-volume[120486]: DEBUG oslo_concurrency.processutils [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Running cmd (subprocess): sudo cind
er-rootwrap /etc/cinder/rootwrap.conf env LC_ALL=C lvs --noheadings --unit=g -o vg_name,name,size --nosuffix yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62 {{(pid=120585) execute /usr/
lib/python2.7/site-packages/oslo_concurrency/processutils.py:372}}
Sep 13 10:28:27 localhost.localdomain sudo[123128]: stack : TTY=unknown ; PWD=/ ; USER=root ; COMMAND=/usr/bin/cinder-rootwrap /etc/cinder/rootwrap.conf env LC_ALL=C lvs --noheadings --un
it=g -o vg_name,name,size --nosuffix yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62
Sep 13 10:28:28 localhost.localdomain cinder-volume[120486]: DEBUG oslo_concurrency.processutils [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] CMD "sudo cinder-rootwrap /etc/cind
er/rootwrap.conf env LC_ALL=C lvs --noheadings --unit=g -o vg_name,name,size --nosuffix yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62" returned: 0 in 0.233s {{(pid=120585) execute /us
r/lib/python2.7/site-packages/oslo_concurrency/processutils.py:409}}
Sep 13 10:28:28 localhost.localdomain cinder-volume[120486]: DEBUG oslo_concurrency.processutils [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] Running cmd (subprocess): sudo cind
er-rootwrap /etc/cinder/rootwrap.conf env LC_ALL=C lvcreate --name volume-48ad9897-5349-4cf8-b393-a8043d2f437b --snapshot yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62 {{(pid=120585)
execute /usr/lib/python2.7/site-packages/oslo_concurrency/processutils.py:372}}
Sep 13 10:28:28 localhost.localdomain sudo[123138]: stack : TTY=unknown ; PWD=/ ; USER=root ; COMMAND=/usr/bin/cinder-rootwrap /etc/cinder/rootwrap.conf env LC_ALL=C lvcreate --name volum
e-48ad9897-5349-4cf8-b393-a8043d2f437b --snapshot yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62
Sep 13 10:28:28 localhost.localdomain cinder-volume[120486]: DEBUG oslo_concurrency.processutils [None req-0b52c6f7-334b-42da-834e-9fb6c4d2e875 None None] CMD "sudo cinder-rootwrap /etc/cind
er/rootwrap.conf env LC_ALL=C lvcreate --name volume-48ad9897-5349-4cf8-b393-a8043d2f437b --snapshot yenai_vg/volume-ea5d357c-10a3-46c5-aee6-7e2281717f62" returned: 0 in 0.261s {{(pid=120585) execute /usr/lib/python2.7/site-packages/oslo_concurrency/processutils.py:409}}

The size is wrong in cinder DB, actually we must not allow to create a volume smaller then 8GB.
In my ceph env, it will do extend(reduce the size) which causing creating a smaller and unusable boot volume.
It's terrible!!!