I don't think that all pages of virtual mapping in removed memory can be
freed, since page which type is MIX_SECTION_INFO is difficult to free.
So, the patch only frees page which type is SECTION_INFO at first.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
CC: Wen Congyang <redacted>
Signed-off-by: Yasuaki Ishimatsu <redacted>

---
 arch/x86/mm/init_64.c |   91 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mm.h    |    2 +
 mm/memory_hotplug.c   |    5 ++
 mm/sparse.c           |    5 +-
 4 files changed, 101 insertions(+), 2 deletions(-)

Index: linux-3.5-rc4/include/linux/mm.h
===================================================================

--- linux-3.5-rc4.orig/include/linux/mm.h	2012-07-03 14:22:18.530011567 +0900
+++ linux-3.5-rc4/include/linux/mm.h	2012-07-03 14:22:20.999983872 +0900

@@ -1588,6 +1588,8 @@ int vmemmap_populate(struct page *start_
 void vmemmap_populate_print_last(void);
 void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
 				  unsigned long size);
+void vmemmap_kfree(struct page *memmpa, unsigned long nr_pages);
+void vmemmap_free_bootmem(struct page *memmpa, unsigned long nr_pages);

 enum mf_flags {
 	MF_COUNT_INCREASED = 1 << 0,

Index: linux-3.5-rc4/mm/sparse.c
===================================================================

--- linux-3.5-rc4.orig/mm/sparse.c	2012-07-03 14:21:45.071429805 +0900
+++ linux-3.5-rc4/mm/sparse.c	2012-07-03 14:22:21.000983767 +0900

@@ -614,12 +614,13 @@ static inline struct page *kmalloc_secti
 	/* This will make the necessary allocations eventually. */
 	return sparse_mem_map_populate(pnum, nid);
 }
-static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
+static void __kfree_section_memmap(struct page *page, unsigned long nr_pages)
 {
-	return; /* XXX: Not implemented yet */
+	vmemmap_kfree(page, nr_pages);

 #else
 static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
Index: linux-3.5-rc4/arch/x86/mm/init_64.c
===================================================================

--- linux-3.5-rc4.orig/arch/x86/mm/init_64.c	2012-07-03 14:22:18.538011465 +0900
+++ linux-3.5-rc4/arch/x86/mm/init_64.c	2012-07-03 14:22:21.007983103 +0900

@@ -978,6 +978,97 @@ vmemmap_populate(struct page *start_page
 	return 0;
 }

+unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
+				      struct page **pp)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	unsigned long next;
+
+	*pp = NULL;
+
+	pgd = pgd_offset_k(addr);
+	if (pgd_none(*pgd))
+		return (addr + PAGE_SIZE) & PAGE_MASK;

+		}
+	}
+}
+
+void __meminit
+vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
+{
+	unsigned long addr = (unsigned long)memmap;
+	unsigned long end = (unsigned long)(memmap + nr_pages);
+	unsigned long next;
+	struct page *page;
+	unsigned long magic;
+
+	for (; addr < end; addr = next) {
+		page = NULL;
+		next = find_and_clear_pte_page(addr, end, &page);
+		if (!page)
+			continue;
+
+		magic = (unsigned long) page->lru.next;
+		if (magic == SECTION_INFO)
+			put_page_bootmem(page);
+	}
+}
+
 void __meminit
 register_page_bootmem_memmap(unsigned long section_nr, struct page *start_page,
 			     unsigned long size)
Index: linux-3.5-rc4/mm/memory_hotplug.c
===================================================================

--- linux-3.5-rc4.orig/mm/memory_hotplug.c	2012-07-03 14:22:18.522011667 +0900
+++ linux-3.5-rc4/mm/memory_hotplug.c	2012-07-03 14:22:21.012982694 +0900

@@ -303,6 +303,8 @@ static int __meminit __add_section(int n
 #ifdef CONFIG_SPARSEMEM_VMEMMAP

 static int __remove_section(struct zone *zone, struct mem_section *ms)
 {
+	unsigned long flags;
+	struct pglist_data *pgdat = zone->zone_pgdat;
 	int ret;

 	if (!valid_section(ms))

@@ -310,6 +312,9 @@ static int __remove_section(struct zone

 	ret = unregister_memory_section(ms);

+	pgdat_resize_lock(pgdat, &flags);
+	sparse_remove_one_section(zone, ms);
+	pgdat_resize_unlock(pgdat, &flags);
 	return ret;
 }
 #else