Building with the attached random configuration file, fs/built-in.o: In function `btrfs_csum_data': /home/jim/linux/fs/btrfs/disk-io.c:247: undefined reference to `crc32c' /home/jim/linux/fs/btrfs/disk-io.c:247: undefined reference to `crc32c' /home/jim/linux/fs/btrfs/disk-io.c:247: undefined reference to `crc32c' /home/jim/linux/fs/btrfs/disk-io.c:247: undefined reference to `crc32c' fs/built-in.o: In function `send_cmd': /home/jim/linux/fs/btrfs/send.c:623: undefined reference to `crc32c' fs/built-in.o:/home/jim/linux/fs/btrfs/check-integrity.c:1826: more undefined re ferences to `crc32c' follow make: *** [vmlinux] Error 1