bcache Backing Device Gets Registered But Not Started

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Environment

SUSE Linux Enterprise Server 12

Situation

The bcache backing device gets registered but not started. Registering works as the kernel logs "register_bdev() registered backing device" but neither /dev/bcache0 nor /sys/block/bcache0 are created and so there is no means to shutdown this device. Usage counter for bcache module is increased, so unloading module does not work. Rebooting also does not help as the error persists.

Resolution

First verify that the bcache backing device is in the invalid state by running:

bcache-super-show <device>

If the dev.data.cache_state state is clean and the cset.uuid consists only of zeros, the bcache device is in the invalid state and must be recreated.

To recreate the bcache device, first ensure the bcache module is unloaded, and then write a new header to the device as follows:

make-bcache -B

This issue is caused by a bug in the bcache kernel module. This bug has been resolved in SLES 12 kernel version 3.12.51-52.34.1. To avoid this issue, install this SLES 12 kernel update (or newer).

Disclaimer

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