Brian Norris [off-list ref] wrote:

I'm looking to use roundup_pow_of_two() (actually, order_base_2())
from <linux/log2.h>, but it seems that it only supports 64-bit integers
if your toolchain uses a 64-bit 'unsigned long' type. This is strange,
considering that ilog2() is explicitly designed for 32-bit or 64-bit
compatibility.

ilog2() was explicitly designed for use with 'unsigned long'.  See the commit
description (f0d1b0b30d250a07627ad8b9fbbb5c7cc08422e8).  It may work with
unsigned long long, however...

David