mm: pass the vmem_altmap to arch_remove_memory and __remove_pages

We can just pass this on instead of having to do a radix tree lookup
without proper locking 2 levels into the callchain.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

arch/powerpc/mm/mem.c

@@ -149,11 +149,10 @@ int arch_add_memory(int nid, u64 start, u64 size, struct vmem_altmap *altmap,
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-int arch_remove_memory(u64 start, u64 size)
+int arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
 {
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
-	struct vmem_altmap *altmap;
 	struct page *page;
 	int ret;
 
@@ -162,11 +161,10 @@ int arch_remove_memory(u64 start, u64 size)
 	 * when querying the zone.
 	 */
 	page = pfn_to_page(start_pfn);
-	altmap = to_vmem_altmap((unsigned long) page);
 	if (altmap)
 		page += vmem_altmap_offset(altmap);
 
-	ret = __remove_pages(page_zone(page), start_pfn, nr_pages);
+	ret = __remove_pages(page_zone(page), start_pfn, nr_pages, altmap);
 	if (ret)
 		return ret;