mm/memory_hotplug: poison memmap in remove_pfn_range_from_zone()

Let's poison the pages similar to when adding new memory in
sparse_add_section().  Also call remove_pfn_range_from_zone() from
memunmap_pages(), so we can poison the memmap from there as well.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Logan Gunthorpe <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Pankaj Gupta <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/memory_hotplug.c

@@ -490,6 +490,9 @@ void __ref remove_pfn_range_from_zone(struct zone *zone,
 	struct pglist_data *pgdat = zone->zone_pgdat;
 	unsigned long flags;
 
+	/* Poison struct pages because they are now uninitialized again. */
+	page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
+
 #ifdef CONFIG_ZONE_DEVICE
 	/*
 	 * Zone shrinking code cannot properly deal with ZONE_DEVICE. So

mm/memremap.c

@@ -120,6 +120,8 @@ void memunmap_pages(struct dev_pagemap *pgmap)
 	nid = page_to_nid(first_page);
 
 	mem_hotplug_begin();
+	remove_pfn_range_from_zone(page_zone(first_page), PHYS_PFN(res->start),
+				   PHYS_PFN(resource_size(res)));
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
 		__remove_pages(PHYS_PFN(res->start),
 			       PHYS_PFN(resource_size(res)), NULL);