Clone target (EXPERIMENTAL)

modulename: dm-clone.ko

configname: CONFIG_DM_CLONE

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>Clone target (EXPERIMENTAL)
In linux kernel since version 5.1 (release Date: 2019-05-05)  
dm-clone produces a one-to-one copy of an existing, read-only source
device into a writable destination device. The cloned device is
visible/mountable immediately and the copy of the source device to the
destination device happens in the background, in parallel with user

If unsure, say N.

source code: