Comment 2 for bug 1653080

_is_booted_from_volume should always return False for instances booting from an image, even when the image is using the rbd imagebackend. As Mitaka is now only security-supported I had a quick look to see if this would reproduce against master and everything WORKSFORME :

$ pwd
/opt/stack/nova
$ git rev-parse HEAD
d768bfa2c2fb774154a5268f58b28537f7b39f69

$ nova flavor-list
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| ID | Name | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public |
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| 1 | m1.tiny | 512 | 1 | 0 | | 1 | 1.0 | True |
[..]
| d1 | ds512M | 512 | 5 | 0 | | 1 | 1.0 | True |
[..]
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
$ nova boot --image cirros-raw --flavor 1 test-resize
$ nova resize test-resize d1
$ sudo rbd -p vms ls -l
NAME SIZE PARENT FMT PROT LOCK
67e542f2-6a21-4363-818b-4ed58be529dd_disk 5120M images/ec027d6b-f677-40fd-b3c9-f0d30ef460de@snap 2
67e542f2-6a21-4363-818b-4ed58be529dd_disk@nova-resize 1024M images/ec027d6b-f677-40fd-b3c9-f0d30ef460de@snap 2
$ nova resize-confirm test-resize
$ sudo rbd -p vms ls -l
NAME SIZE PARENT FMT PROT LOCK
67e542f2-6a21-4363-818b-4ed58be529dd_disk 5120M images/ec027d6b-f677-40fd-b3c9-f0d30ef460de@snap 2

I can't see anything obvious going back to Mitaka regarding rbd imagebackend resizes. If this still reproduces for you on Mitaka, Newton or master can you provide an example n-cpu.log for review?