Comment 49 for bug 1729145

Artful verified:

ubuntu@ubuntu:~$ lsb_release -rd
Description: Ubuntu 17.10
Release: 17.10
ubuntu@ubuntu:~$ uname -a
Linux ubuntu 4.13.0-38-generic #43-Ubuntu SMP Wed Mar 14 15:20:44 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
ubuntu@ubuntu:~$ apt-cache policy linux-image-virtual
linux-image-virtual:
  Installed: 4.13.0.38.41
  Candidate: 4.13.0.38.41
  Version table:
 *** 4.13.0.38.41 500
        500 http://archive.ubuntu.com/ubuntu artful-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     4.13.0.37.40 500
        500 http://archive.ubuntu.com/ubuntu artful-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu artful-security/main amd64 Packages
     4.13.0.16.17 500
        500 http://archive.ubuntu.com/ubuntu artful/main amd64 Packages

ubuntu@ubuntu:~$ ls -al /dev/bcache/by-*
/dev/bcache/by-label:
total 0
drwxr-xr-x 2 root root 120 Mar 19 18:32 .
drwxr-xr-x 4 root root 80 Mar 19 18:32 ..
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdb -> ../../bcache1
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdd -> ../../bcache0
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sde -> ../../bcache3
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdf -> ../../bcache2

/dev/bcache/by-uuid:
total 0
drwxr-xr-x 2 root root 120 Mar 19 18:32 .
drwxr-xr-x 4 root root 80 Mar 19 18:32 ..
lrwxrwxrwx 1 root root 13 Mar 19 18:32 1f531b44-437f-49cc-b7db-16db6d699c41 -> ../../bcache2
lrwxrwxrwx 1 root root 13 Mar 19 18:32 31474eb7-687d-4bb7-8c6b-b4efd472e860 -> ../../bcache1
lrwxrwxrwx 1 root root 13 Mar 19 18:32 3653ce1f-b6aa-43ad-9a91-506530db2d50 -> ../../bcache0
lrwxrwxrwx 1 root root 13 Mar 19 18:32 94041d44-4bb2-4e4d-8641-21d4ae410595 -> ../../bcache3

ubuntu@ubuntu:~$ ls -al /dev/bcache/by-label/
total 0
drwxr-xr-x 2 root root 120 Mar 19 18:32 .
drwxr-xr-x 4 root root 80 Mar 19 18:32 ..
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdb -> ../../bcache1
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdd -> ../../bcache0
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sde -> ../../bcache3
lrwxrwxrwx 1 root root 13 Mar 19 18:32 backing-sdf -> ../../bcache2

ubuntu@ubuntu:~$ ls -al /dev/bcache/by-label/backing-sdb
lrwxrwxrwx 1 root root 13 Mar 19 18:32 /dev/bcache/by-label/backing-sdb -> ../../bcache1
ubuntu@ubuntu:~$ ls -al /sys/class/block/bcache1/slaves/
total 0
drwxr-xr-x 2 root root 0 Mar 19 18:36 .
drwxr-xr-x 8 root root 0 Mar 19 18:36 ..
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sda -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:0/2:0:0:0/block/sda
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sdb -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:1/2:0:1:0/block/sdb
ubuntu@ubuntu:~$ ls -al /dev/bcache/by-label/backing-sdd
lrwxrwxrwx 1 root root 13 Mar 19 18:32 /dev/bcache/by-label/backing-sdd -> ../../bcache0
ubuntu@ubuntu:~$ ls -al /sys/class/block/bcache0/slaves/
total 0
drwxr-xr-x 2 root root 0 Mar 19 18:36 .
drwxr-xr-x 8 root root 0 Mar 19 18:36 ..
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sda -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:0/2:0:0:0/block/sda
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sdd -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:3/2:0:3:0/block/sdd
ubuntu@ubuntu:~$ ls -al /dev/bcache/by-label/backing-sde
lrwxrwxrwx 1 root root 13 Mar 19 18:32 /dev/bcache/by-label/backing-sde -> ../../bcache3
ubuntu@ubuntu:~$ ls -al /sys/class/block/bcache3/slaves/
total 0
drwxr-xr-x 2 root root 0 Mar 19 18:36 .
drwxr-xr-x 8 root root 0 Mar 19 18:36 ..
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sdc -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:2/2:0:2:0/block/sdc
lrwxrwxrwx 1 root root 0 Mar 19 18:36 sde -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:4/2:0:4:0/block/sde
ubuntu@ubuntu:~$ ls -al /dev/bcache/by-label/backing-sdf
lrwxrwxrwx 1 root root 13 Mar 19 18:32 /dev/bcache/by-label/backing-sdf -> ../../bcache2
ubuntu@ubuntu:~$ ls -al /sys/class/block/bcache2/slaves/
total 0
drwxr-xr-x 2 root root 0 Mar 19 18:37 .
drwxr-xr-x 8 root root 0 Mar 19 18:32 ..
lrwxrwxrwx 1 root root 0 Mar 19 18:37 sdc -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:2/2:0:2:0/block/sdc
lrwxrwxrwx 1 root root 0 Mar 19 18:37 sdf -> ../../../../pci0000:00/0000:00:04.0/virtio1/host2/target2:0:5/2:0:5:0/block/sdf

$ dmesg | grep bcache
[ 1.210989] bcache: register_bdev() registered backing device sdd
[ 1.214956] bcache: bch_journal_replay() journal replay done, 0 keys in 2 entries, seq 9
[ 1.216142] bcache: register_cache() registered cache device sdc
[ 1.216436] bcache: register_bdev() registered backing device sdb
[ 1.220348] bcache: bch_journal_replay() journal replay done, 0 keys in 2 entries, seq 9
[ 1.233925] bcache: bch_cached_dev_attach() Caching sdb as bcache1 on set 0dbdcc17-7af0-4318-bd57-bbdf5c7f1bfa
[ 1.270172] bcache: bch_cached_dev_attach() Caching sdd as bcache0 on set 0dbdcc17-7af0-4318-bd57-bbdf5c7f1bfa
[ 1.272236] bcache: register_cache() registered cache device sda
[ 1.272410] bcache: register_bdev() registered backing device sdf
[ 1.278563] bcache: bch_cached_dev_attach() Caching sdf as bcache2 on set d36b419d-a49d-42e2-95af-710138a20700
[ 1.282832] bcache: register_bdev() registered backing device sde
[ 1.293573] bcache: bch_cached_dev_attach() Caching sde as bcache3 on set d36b419d-a49d-42e2-95af-710138a20700
[ 4.196288] bcache: register_bcache() error opening /dev/sdf: device already registered (emitting change event)
[ 4.196920] bcache: register_bcache() error opening /dev/sda: device already registered
[ 4.205664] bcache: register_bcache() error opening /dev/sdb: device already registered (emitting change event)
[ 4.205968] bcache: register_bcache() error opening /dev/sdc: device already registered
[ 4.206348] bcache: register_bcache() error opening /dev/sdd: device already registered (emitting change event)
[ 4.208488] bcache: register_bcache() error opening /dev/sde: device already registered (emitting change event)