With the patch, I'm still experiencing problem described in comment 3, but I've seen that only once. I'm also experiencing this:


        finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: SUCCESS: configuring raid: md0
        start: cmd-install/stage-partitioning/builtin/cmd-block-meta: configuring bcache: bcache0
        get_path_to_storage_volume for volume md0
        devsync for /dev/md0
        Running command ['partprobe', '/dev/md0'] with allowed return codes [0, 1] (capture=False)
        Running command ['udevadm', 'settle'] with allowed return codes [0] (capture=False)
        devsync happy - path /dev/md0 now exists
        return volume path /dev/md0
        get_path_to_storage_volume for volume sde
        Processing serial BTHC63800AX9480MGN via udev to BTHC63800AX9480MGN
        devsync for /dev/sde
        Running command ['partprobe', '/dev/sde'] with allowed return codes [0, 1] (capture=False)
        Running command ['udevadm', 'settle'] with allowed return codes [0] (capture=False)
        devsync happy - path /dev/sde now exists
        return volume path /dev/sde
        caching device does not yet exist at /sys/class/block/sde/bcache. Make cache and get uuid
        Running command ['make-bcache', '-C', '/dev/sde'] with allowed return codes [0] (capture=True)
        out=[UUID:                      80409bc0-2339-47f5-97b3-1d27ddc3fdec
        Set UUID:               b8dc8e2e-1b85-4761-9696-b23cb0cb69f0
        version:                0
        nbuckets:               915725
        block_size:             1
        bucket_size:            1024
        nr_in_set:              1
        nr_this_dev:            0
        first_bucket:           1
        ]
        check just created bcache /dev/sde if it is registered, try=1
        Running command ['udevadm', 'settle'] with allowed return codes [0] (capture=False)
        Found bcache dev /dev/sde at expected path /sys/fs/bcache/b8dc8e2e-1b85-4761-9696-b23cb0cb69f0
        validating bcache caching device '/dev/sde' from sys_path '/sys/fs/bcache/b8dc8e2e-1b85-4761-9696-b23cb0cb69f0'
        Resolving symlink /sys/fs/bcache/b8dc8e2e-1b85-4761-9696-b23cb0cb69f0/cache0 -> ../../../devices/pci0000:00/0000:00:02.0/0000:03:00.0/host0/port-0:0/expander-0:0/port-0:0:4/end_device-0:0:4/target0:0:4/0:0:4:0/block/sde/bcache
        Found match: bcache_device=/dev/sde target_device=sde
        bcache dev /dev/sde at path /sys/fs/bcache/b8dc8e2e-1b85-4761-9696-b23cb0cb69f0 successfully registered on attempt 1/60
        An error occured handling 'bcache0': RuntimeError - ('Unexpected old bcache device: %s', '/dev/md0')
        finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: configuring bcache: bcache0
        finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: curtin command block-meta
        Traceback (most recent call last):
          File "/curtin/curtin/commands/main.py", line 215, in main
            ret = args.func(args)
          File "/curtin/curtin/commands/block_meta.py", line 67, in block_meta
            meta_custom(args)
          File "/curtin/curtin/commands/block_meta.py", line 1243, in meta_custom
            handler(command, storage_config_dict)
          File "/curtin/curtin/commands/block_meta.py", line 1119, in bcache_handler
            'Unexpected old bcache device: %s', backing_device)
        RuntimeError: ('Unexpected old bcache device: %s', '/dev/md0')
        ('Unexpected old bcache device: %s', '/dev/md0')