Chris Down writes:
"mm: move nr_deactivate accounting to shrink_active_list()" uses the non-irqsaved version of count_memcg_events (__count_memcg_events), but we've only exported the irqsaving version of it to userspace, so the build breaks:
Er, "with !CONFIG_MEMCG", not "to userspace". No idea where that came from...