[S390] memory hotplug: prevent memory zone interleave

This fixes a kernel oops with CONFIG_DEBUG_VM triggered by a
VM_BUG_ON(bad_range()): kernel BUG at mm/page_alloc.c:748.

With memory hotplug on System z, it is possible that the memory
online/offline state is preserved over a system restart, e.g. there
may be offline memory blocks in ZONE_DMA or ZONE_NORMAL. So far,
the offline memory range has always been added to ZONE_MOVABLE during
system start, so that it was possible to have ZONE_MOVABLE interleave
with ZONE_DMA or ZONE_NORMAL. This patch fixes that by checking for
zone overlap before adding memory.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 26 insertions, 4 deletions

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 5d633019d8f3..50236610de83 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -223,16 +223,38 @@ void free_initrd_mem(unsigned long start, unsigned long end)
 #ifdef CONFIG_MEMORY_HOTPLUG
 int arch_add_memory(int nid, u64 start, u64 size)
 {
-        struct pglist_data *pgdat;
+        unsigned long zone_start_pfn, zone_end_pfn, nr_pages;
+        unsigned long start_pfn = PFN_DOWN(start);
+        unsigned long size_pages = PFN_DOWN(size);
         struct zone *zone;
         int rc;
 
-        pgdat = NODE_DATA(nid);
-        zone = pgdat->node_zones + ZONE_MOVABLE;
         rc = vmem_add_mapping(start, size);
         if (rc)
                 return rc;
-        rc = __add_pages(nid, zone, PFN_DOWN(start), PFN_DOWN(size));
+        for_each_zone(zone) {
+                if (zone_idx(zone) != ZONE_MOVABLE) {
+                        /* Add range within existing zone limits */
+                        zone_start_pfn = zone->zone_start_pfn;
+                        zone_end_pfn = zone->zone_start_pfn +
+                                       zone->spanned_pages;
+                } else {
+                        /* Add remaining range to ZONE_MOVABLE */
+                        zone_start_pfn = start_pfn;
+                        zone_end_pfn = 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);
         return rc;