mm/sparsemem: fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

We pass the number of pages which hold page structs of a memory section
to free_map_bootmem().  This is right when !CONFIG_SPARSEMEM_VMEMMAP but
wrong when CONFIG_SPARSEMEM_VMEMMAP.  When CONFIG_SPARSEMEM_VMEMMAP, we
should pass the number of pages of a memory section to free_map_bootmem.

So the fix is removing the nr_pages parameter.  When
CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
PAGES_PER_SECTION in free_map_bootmem.  When !CONFIG_SPARSEMEM_VMEMMAP,
we calculate page numbers needed to hold the page structs for a memory
section and use the value in free_map_bootmem().

This was found by reading the code.  And I have no machine that support
memory hot-remove to test the bug now.
Signed-off-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Reviewed-by: NWanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/sparse.c

@@ -603,10 +603,10 @@ static void __kfree_section_memmap(struct page *memmap)
 	vmemmap_free(start, end);
 }
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
+static void free_map_bootmem(struct page *memmap)
 {
 	unsigned long start = (unsigned long)memmap;
-	unsigned long end = (unsigned long)(memmap + nr_pages);
+	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
 
 	vmemmap_free(start, end);
 }
@@ -648,12 +648,15 @@ static void __kfree_section_memmap(struct page *memmap)
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
+static void free_map_bootmem(struct page *memmap)
 {
 	unsigned long maps_section_nr, removing_section_nr, i;
-	unsigned long magic;
+	unsigned long magic, nr_pages;
 	struct page *page = virt_to_page(memmap);
 
+	nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
+		>> PAGE_SHIFT;
+
 	for (i = 0; i < nr_pages; i++, page++) {
 		magic = (unsigned long) page->lru.next;
 
@@ -756,7 +759,6 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 {
 	struct page *usemap_page;
-	unsigned long nr_pages;
 
 	if (!usemap)
 		return;
@@ -777,12 +779,8 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 	 * on the section which has pgdat at boot time. Just keep it as is now.
 	 */
 
-	if (memmap) {
-		nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
-			>> PAGE_SHIFT;
-
-		free_map_bootmem(memmap, nr_pages);
-	}
+	if (memmap)
+		free_map_bootmem(memmap);
 }
 
 void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)