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: Len Brown <len.br...@intel.com>
CC: Benjamin Herrenschmidt <b...@kernel.crashing.org>
CC: Paul Mackerras <pau...@samba.org>
CC: Christoph Lameter <c...@linux.com>
Cc: Minchan Kim <minchan....@gmail.com>
CC: Andrew Morton <a...@linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com>
CC: Wen Congyang <we...@cn.fujitsu.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasu...@jp.fujitsu.com>

---
 arch/x86/mm/init_64.c |   89 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mm.h    |    2 +
 mm/memory_hotplug.c   |    5 ++
 mm/sparse.c           |    5 +-
 4 files changed, 99 insertions(+), 2 deletions(-)

Index: linux-3.5-rc4/include/linux/mm.h
===================================================================
--- linux-3.5-rc4.orig/include/linux/mm.h       2012-06-27 09:11:13.790150442 
+0900
+++ linux-3.5-rc4/include/linux/mm.h    2012-06-27 09:11:16.433117400 +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      2012-06-27 09:06:35.317631878 +0900
+++ linux-3.5-rc4/mm/sparse.c   2012-06-27 09:11:16.434117388 +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);
 }
 static void free_map_bootmem(struct page *page, unsigned long nr_pages)
 {
+       vmemmap_free_bootmem(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    2012-06-27 09:11:13.791150430 
+0900
+++ linux-3.5-rc4/arch/x86/mm/init_64.c 2012-06-27 09:11:59.254581998 +0900
@@ -978,6 +978,95 @@ vmemmap_populate(struct page *start_page
        return 0;
 }

+unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
+                                     struct page *page)
+{
+       pgd_t *pgd;
+       pud_t *pud;
+       pmd_t *pmd;
+       pte_t *pte;
+       unsigned long next;
+
+       page = NULL;
+
+       pgd = pgd_offset_k(addr);
+       if (pgd_none(*pgd))
+               return PAGE_SIZE;
+
+       pud = pud_offset(pgd, addr);
+       if (pud_none(*pud))
+               return PAGE_SIZE;
+
+       if (!cpu_has_pse) {
+               next = (addr + PAGE_SIZE) & PAGE_MASK;
+               pmd = pmd_offset(pud, addr);
+               if (pmd_none(*pmd))
+                       return next;
+
+               pte = pte_offset_kernel(pmd, addr);
+               if (pte_none(*pte))
+                       return next;
+
+               page = pte_page(*pte);
+               pte_clear(&init_mm, addr, pte);
+       } else {
+               next = pmd_addr_end(addr, end);
+
+               pmd = pmd_offset(pud, addr);
+               if (pmd_none(*pmd))
+                       return next;
+
+               page = pmd_page(*pmd);
+               pmd_clear(pmd);
+       }
+
+       return next;
+}
+
+void __meminit
+vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
+{
+       unsigned long addr = (unsigned long)memmap;
+       unsigned long end = (unsigned long)(memmap + nr_pages);
+       unsigned long next;
+       unsigned int order;
+       struct page *page;
+
+       for (; addr < end; addr = next) {
+               next = find_and_clear_pte_page(addr, end, page);
+               if (!page)
+                       continue;
+
+               if (is_vmalloc_addr(page))
+                       vfree(page);
+               else {
+                       order = next - addr;
+                       free_pages((unsigned long)page,
+                                  get_order(sizeof(struct page) *  order));
+               }
+       }
+}
+
+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) {
+               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      2012-06-27 09:11:13.789150454 
+0900
+++ linux-3.5-rc4/mm/memory_hotplug.c   2012-06-27 09:11:16.436117363 +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

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