config DM_PERSISTENT_DATA       tristate       depends on BLK_DEV_DM       select LIBCRC32C       select DM_BUFIO       ---help---	 Library providing immutable on-disk data structure support for	 device-mapper targets such as the thin provisioning target. config DM_DEBUG_BLOCK_STACK_TRACING       boolean "Keep stack trace of persistent data block lock holders"       depends on STACKTRACE_SUPPORT && DM_PERSISTENT_DATA       select STACKTRACE       ---help---	 Enable this for messages that may help debug problems with the	 block manager locking used by thin provisioning and caching. 	 If unsure, say N.