When you compile a program that need to include kernel sources, sometimes the compile might give you an warning message like below:

 *   CONFIG_SYSFS_DEPRECATED:     should not be set. But it is.
 *   CONFIG_SYSFS_DEPRECATED_V2:     should not be set. But it is.

To fix this, you will need to recompile your kernel using menuconfig, and find

When you compile your own kernel, in order to enable support for dm-crypt, please make sure you check

Device Drivers --->
     [*] Multiple devices driver support (RAID and LVM) --->
        <*> Device mapper support
        <*> Crypt target support