mm/page_alloc.c: check return value of memblock_alloc_node_nopanic()

There are two early memory allocations that use
memblock_alloc_node_nopanic() and do not check its return value.

While this happens very early during boot and chances that the
allocation will fail are diminishing, it is still worth to have proper
checks for the allocation errors.

Link: http://lkml.kernel.org/r/1547734941-944-1-git-send-email-rppt@linux.ibm.comSigned-off-by: NMike Rapoport <rppt@linux.ibm.com>
Reviewed-by: NWilliam Kucharski <william.kucharski@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -6431,10 +6431,14 @@ static void __ref setup_usemap(struct pglist_data *pgdat,
 {
 	unsigned long usemapsize = usemap_size(zone_start_pfn, zonesize);
 	zone->pageblock_flags = NULL;
-	if (usemapsize)
+	if (usemapsize) {
 		zone->pageblock_flags =
 			memblock_alloc_node_nopanic(usemapsize,
 							 pgdat->node_id);
+		if (!zone->pageblock_flags)
+			panic("Failed to allocate %ld bytes for zone %s pageblock flags on node %d\n",
+			      usemapsize, zone->name, pgdat->node_id);
+	}
 }
 #else
 static inline void setup_usemap(struct pglist_data *pgdat, struct zone *zone,
@@ -6664,6 +6668,9 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat)
 		end = ALIGN(end, MAX_ORDER_NR_PAGES);
 		size =  (end - start) * sizeof(struct page);
 		map = memblock_alloc_node_nopanic(size, pgdat->node_id);
+		if (!map)
+			panic("Failed to allocate %ld bytes for node %d memory map\n",
+			      size, pgdat->node_id);
 		pgdat->node_mem_map = map + offset;
 	}
 	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",