s390/mm: fix zone calculation in arch_add_memory()

Standby (hotplug) memory should be added to ZONE_MOVABLE on s390. After
commit 199071f1 "s390/mm: make arch_add_memory() NUMA aware",
arch_add_memory() used memblock_end_of_DRAM() to find out the end of
ZONE_NORMAL and the beginning of ZONE_MOVABLE. However, commit 7f36e3e5
"memory-hotplug: add hot-added memory ranges to memblock before allocate
node_data for a node." moved the call of memblock_add_node() before
the call of arch_add_memory() in add_memory_resource(), and thus changed
the return value of memblock_end_of_DRAM() when called in
arch_add_memory(). As a result, arch_add_memory() will think that all
memory blocks should be added to ZONE_NORMAL.

Fix this by changing the logic in arch_add_memory() so that it will
manually iterate over all zones of a given node to find out which zone
a memory block should be added to.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/init.c

@@ -151,36 +151,40 @@ void __init free_initrd_mem(unsigned long start, unsigned long end)
 #ifdef CONFIG_MEMORY_HOTPLUG
 int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
 {
-	unsigned long normal_end_pfn = PFN_DOWN(memblock_end_of_DRAM());
-	unsigned long dma_end_pfn = PFN_DOWN(MAX_DMA_ADDRESS);
+	unsigned long zone_start_pfn, zone_end_pfn, nr_pages;
 	unsigned long start_pfn = PFN_DOWN(start);
 	unsigned long size_pages = PFN_DOWN(size);
-	unsigned long nr_pages;
-	int rc, zone_enum;
+	pg_data_t *pgdat = NODE_DATA(nid);
+	struct zone *zone;
+	int rc, i;
 
 	rc = vmem_add_mapping(start, size);
 	if (rc)
 		return rc;
 
-	while (size_pages > 0) {
-		if (start_pfn < dma_end_pfn) {
-			nr_pages = (start_pfn + size_pages > dma_end_pfn) ?
-				   dma_end_pfn - start_pfn : size_pages;
-			zone_enum = ZONE_DMA;
-		} else if (start_pfn < normal_end_pfn) {
-			nr_pages = (start_pfn + size_pages > normal_end_pfn) ?
-				   normal_end_pfn - start_pfn : size_pages;
-			zone_enum = ZONE_NORMAL;
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		zone = pgdat->node_zones + i;
+		if (zone_idx(zone) != ZONE_MOVABLE) {
+			/* Add range within existing zone limits, if possible */
+			zone_start_pfn = zone->zone_start_pfn;
+			zone_end_pfn = zone->zone_start_pfn +
+				       zone->spanned_pages;
 		} else {
-			nr_pages = size_pages;
-			zone_enum = ZONE_MOVABLE;
+			/* Add remaining range to ZONE_MOVABLE */
+			zone_start_pfn = start_pfn;
+			zone_end_pfn = start_pfn + size_pages;
 		}
-		rc = __add_pages(nid, NODE_DATA(nid)->node_zones + zone_enum,
-				 start_pfn, size_pages);
+		if (start_pfn < zone_start_pfn || start_pfn >= zone_end_pfn)
+			continue;
+		nr_pages = (start_pfn + size_pages > zone_end_pfn) ?
+			   zone_end_pfn - start_pfn : size_pages;
+		rc = __add_pages(nid, zone, start_pfn, nr_pages);
 		if (rc)
 			break;
 		start_pfn += nr_pages;
 		size_pages -= nr_pages;
+		if (!size_pages)
+			break;
 	}
 	if (rc)
 		vmem_remove_mapping(start, size);