This module is written for Linux kernel 6.6.9-200.fc39.x86_64. Tested and compiled on Fedora CoreOS and GCC 13.2.1.

Compilation

make

Install

sudo insmod dmp.ko

Check that the module is installed

lsmod | grep dmp

Test

./run_test.sh

This is what the script does:

dmsetup create zero1 --table "0 4096 zero"  //create zero block device
dmsetup create dmp1 --table "0 4096 dmp /dev/mapper/zero1"  //create device mapper proxy
dd if=/dev/random of=/dev/mapper/dmp1 bs=4k count=1 //write in dmp1 -> zero1
dd of=/dev/null if=/dev/mapper/dmp1 bs=4k count=1   //read from the dmp1 -> zero1
cat /sys/module/dmp/stat/volumes    //log output

You can use any of these commands individually.

For clear your system after testing kernel module. Run

./clr.sh

The script removes block devices, and it will also ask if you want to remove the dmp.ko module If you choice yes and filesystem write smth or kernel a litle bit crush, don't panic it's normal(i think). This may happen because a module is removed while the kernel is running, it seems it doesn’t really like this. You can also just reboot, everything will clear itself.