hugetlb, rmap: add reverse mapping for hugepage

This patch adds reverse mapping feature for hugepage by introducing
mapcount for shared/private-mapped hugepage and anon_vma for
private-mapped hugepage.

While hugepage is not currently swappable, reverse mapping can be useful
for memory error handler.

Without this patch, memory error handler cannot identify processes
using the bad hugepage nor unmap it from them. That is:
- for shared hugepage:
  we can collect processes using a hugepage through pagecache,
  but can not unmap the hugepage because of the lack of mapcount.
- for privately mapped hugepage:
  we can neither collect processes nor unmap the hugepage.
This patch solves these problems.

This patch include the bug fix given by commit 23be7468e8, so reverts it.

Dependency:
  "hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h"

ChangeLog since May 24.
- create hugetlb_inline.h and move is_vm_hugetlb_index() in it.
- move functions setting up anon_vma for hugepage into mm/rmap.c.

ChangeLog since May 13.
- rebased to 2.6.34
- fix logic error (in case that private mapping and shared mapping coexist)
- move is_vm_hugetlb_page() into include/linux/mm.h to use this function
  from linear_page_index()
- define and use linear_hugepage_index() instead of compound_order()
- use page_move_anon_rmap() in hugetlb_cow()
- copy exclusive switch of __set_page_anon_rmap() into hugepage counterpart.
- revert commit 24be7468 completely

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Acked-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

4 files changed, 13 insertions, 10 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index d47a7c4..e688fd8 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -99,6 +99,7 @@ static inline void hugetlb_report_meminfo(struct seq_file *m)
 #define is_hugepage_only_range(mm, addr, len)	0
 #define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })
 #define hugetlb_fault(mm, vma, addr, flags)	({ BUG(); 0; })
+#define huge_pte_offset(mm, address)	0
 
 #define hugetlb_change_protection(vma, address, end, newprot)
 
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index b2bd2ba..a547d96 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -282,10 +282,16 @@ static inline loff_t page_offset(struct page *page)
 	return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 }
 
+extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
+				     unsigned long address);
+
 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 					unsigned long address)
 {
-	pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
+	pgoff_t pgoff;
+	if (unlikely(is_vm_hugetlb_page(vma)))
+		return linear_hugepage_index(vma, address);
+	pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 	pgoff += vma->vm_pgoff;
 	return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 }
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 34066ff..2110a81 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -48,15 +48,6 @@
 #define POISON_FREE	0x6b	/* for use-after-free poisoning */
 #define	POISON_END	0xa5	/* end-byte of poisoning */
 
-/********** mm/hugetlb.c **********/
-/*
- * Private mappings of hugetlb pages use this poisoned value for
- * page->mapping. The core VM should not be doing anything with this mapping
- * but futex requires the existence of some page->mapping value even though it
- * is unused if PAGE_MAPPING_ANON is set.
- */
-#define HUGETLB_POISON	((void *)(0x00300300 + POISON_POINTER_DELTA + PAGE_MAPPING_ANON))
-
 /********** arch/$ARCH/mm/init.c **********/
 #define POISON_FREE_INITMEM	0xcc
 
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 7721674..9d50e7e 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -140,6 +140,11 @@ void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned lon
 void page_add_file_rmap(struct page *);
 void page_remove_rmap(struct page *);
 
+void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
+			    unsigned long);
+void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
+				unsigned long);
+
 static inline void page_dup_rmap(struct page *page)
 {
 	atomic_inc(&page->_mapcount);