On Wed, Aug 11, 2021 at 04:41:39PM +0300, Mike Rapoport wrote:

From: Mike Rapoport <redacted>

Since the commit ce6ee46e0f39 ("mm/page_alloc: fix memory map
initialization for descending nodes") initialization of the memory map
relies on availability of zone_to_nid() and zone_set_nid methods to link
struct page to a node.

But in 5.10 zone_to_nid() is only defined for NUMA, but not for
DISCONTIGMEM which causes crashes on m68k systems with two memory banks.

Many thanks for the work done to figure this out and fix it.  Now queued
up.

greg k-h