memblock: make memblock_set_node() also warn about use of MAX_NUMNODES

On an (old) x86 system with SRAT just covering space above 4Gb:

    ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0xfffffffff] hotplug

the commit referenced below leads to this NUMA configuration no longer
being refused by a CONFIG_NUMA=y kernel (previously

    NUMA: nodes only cover 6144MB of your 8185MB e820 RAM. Not used.
    No NUMA configuration found
    Faking a node at [mem 0x0000000000000000-0x000000027fffffff]

was seen in the log directly after the message quoted above), because of
memblock_validate_numa_coverage() checking for NUMA_NO_NODE (only). This
in turn led to memblock_alloc_range_nid()'s warning about MAX_NUMNODES
triggering, followed by a NULL deref in memmap_init() when trying to
access node 64's (NODE_SHIFT=6) node data.

To compensate said change, make memblock_set_node() warn on and adjust
a passed in value of MAX_NUMNODES, just like various other functions
already do.

Fixes: ff6c3d8 ("NUMA: optimize detection of memory with no node id assigned by firmware")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1c8a058c-5365-4f27-a9f1-3aeb7fb3e7b2@suse.com
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>

Author: jbeulich

mm/memblock.c

@@ -1339,6 +1339,10 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
 	int start_rgn, end_rgn;
 	int i, ret;
 
+	if (WARN_ONCE(nid == MAX_NUMNODES,
+		      "Usage of MAX_NUMNODES is deprecated. Use NUMA_NO_NODE instead\n"))
+		nid = NUMA_NO_NODE;
+
 	ret = memblock_isolate_range(type, base, size, &start_rgn, &end_rgn);
 	if (ret)
 		return ret;