Asynchronous device registration

configname: CONFIG_BCACHE_ASYNC_REGISTRATION

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>Asynchronous device registration
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
Add a sysfs file /sys/fs/bcache/register_async. Writing registering
device path into this file will returns immediately and the real
registration work is handled in kernel work queue in asynchronous
way.