Comment 54 for bug 1861941

Alright, summarizing this so far, we have the following fixes landed in Groovy:

udev (systemd pkg):

- 60-persistent-storage.rules: skip_bcache_fs_type:
  - /dev/disk/by-uuid/_ and /dev/disk/by-label/_ not created for bcache devs

Since it does not make sense to have the caching device symlink like if it was a regular filesystem disk to be used:

(k)rafaeldtinoco@bcache:~$ ls -lah /dev/disk/by-uuid
total 0
drwxr-xr-x 2 root root 100 Jul 21 18:49 .
drwxr-xr-x 7 root root 140 Jul 21 17:39 ..
lrwxrwxrwx 1 root root 10 Jul 21 17:39 022E-07E1 -> ../../vda1
lrwxrwxrwx 1 root root 13 Jul 21 18:49 50b98f0d-c0e0-49d2-9856-8ac6bc91e232 -> ../../bcache0
lrwxrwxrwx 1 root root 10 Jul 21 17:39 67993d4f-fa55-49b1-886e-c692f88393ba -> ../../vda2

- 69-bcache.rules:
  - if any other driver - than bcache - touches /dev/bcache[0-9]*
    bcache/by-uuid/_ (BCACHE_CACHED_UUID and LABEL) symlinks are
    recreated.

To address the udev event responsible for wiping /dev/bcache/by-uuid, like:

KERNEL[4175.725930] change /devices/virtual/block/bcache0 (block)
ACTION=change
DEVPATH=/devices/virtual/block/bcache0
SUBSYSTEM=block
SYNTH_UUID=0
DEVNAME=/dev/bcache0
DEVTYPE=disk
SEQNUM=6746
MAJOR=251
MINOR=0

UDEV [4175.758078] change /devices/virtual/block/bcache0 (block)
ACTION=change
DEVPATH=/devices/virtual/block/bcache0
SUBSYSTEM=block
SYNTH_UUID=0
DEVNAME=/dev/bcache0
DEVTYPE=disk
SEQNUM=6746
USEC_INITIALIZED=4151438558
ID_FS_UUID=50b98f0d-c0e0-49d2-9856-8ac6bc91e232
ID_FS_UUID_ENC=50b98f0d-c0e0-49d2-9856-8ac6bc91e232
ID_FS_VERSION=1.0
ID_FS_TYPE=ext4
ID_FS_USAGE=filesystem
MAJOR=251
MINOR=0
DEVLINKS=/dev/disk/by-uuid/50b98f0d-c0e0-49d2-9856-8ac6bc91e232
TAGS=:systemd: