1 files changed, 77 insertions, 11 deletions

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index a485c14ecd5d..bed5f16ba827 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -9,8 +9,12 @@
 
 #include <linux/bitops.h>
 #include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
 #include <linux/sched.h>
-#include <linux/vmstat.h>
+
+struct stable_node;
+struct mem_cgroup;
 
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -34,23 +38,60 @@ static inline void ksm_exit(struct mm_struct *mm)
 /*
  * A KSM page is one of those write-protected "shared pages" or "merged pages"
  * which KSM maps into multiple mms, wherever identical anonymous page content
- * is found in VM_MERGEABLE vmas.  It's a PageAnon page, with NULL anon_vma.
+ * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
+ * anon_vma, but to that page's node of the stable tree.
  */
 static inline int PageKsm(struct page *page)
 {
-        return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
+        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
+                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
+}
+
+static inline struct stable_node *page_stable_node(struct page *page)
+{
+        return PageKsm(page) ? page_rmapping(page) : NULL;
+}
+
+static inline void set_page_stable_node(struct page *page,
+                                        struct stable_node *stable_node)
+{
+        page->mapping = (void *)stable_node +
+                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
 }
 
 /*
- * But we have to avoid the checking which page_add_anon_rmap() performs.
+ * When do_swap_page() first faults in from swap what used to be a KSM page,
+ * no problem, it will be assigned to this vma's anon_vma; but thereafter,
+ * it might be faulted into a different anon_vma (or perhaps to a different
+ * offset in the same anon_vma).  do_swap_page() cannot do all the locking
+ * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
+ * a copy, and leave remerging the pages to a later pass of ksmd.
+ *
+ * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
+ * but what if the vma was unmerged while the page was swapped out?
  */
-static inline void page_add_ksm_rmap(struct page *page)
+struct page *ksm_does_need_to_copy(struct page *page,
+                        struct vm_area_struct *vma, unsigned long address);
+static inline struct page *ksm_might_need_to_copy(struct page *page,
+                        struct vm_area_struct *vma, unsigned long address)
 {
-        if (atomic_inc_and_test(&page->_mapcount)) {
-                page->mapping = (void *) PAGE_MAPPING_ANON;
-                __inc_zone_page_state(page, NR_ANON_PAGES);
-        }
+        struct anon_vma *anon_vma = page_anon_vma(page);
+
+        if (!anon_vma ||
+            (anon_vma == vma->anon_vma &&
+             page->index == linear_page_index(vma, address)))
+                return page;
+
+        return ksm_does_need_to_copy(page, vma, address);
 }
+
+int page_referenced_ksm(struct page *page,
+                        struct mem_cgroup *memcg, unsigned long *vm_flags);
+int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
+int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
+                  struct vm_area_struct *, unsigned long, void *), void *arg);
+void ksm_migrate_page(struct page *newpage, struct page *oldpage);
+
 #else  /* !CONFIG_KSM */
 
 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -73,7 +114,32 @@ static inline int PageKsm(struct page *page)
         return 0;
 }
 
-/* No stub required for page_add_ksm_rmap(page) */
+static inline struct page *ksm_might_need_to_copy(struct page *page,
+                        struct vm_area_struct *vma, unsigned long address)
+{
+        return page;
+}
+
+static inline int page_referenced_ksm(struct page *page,
+                        struct mem_cgroup *memcg, unsigned long *vm_flags)
+{
+        return 0;
+}
+
+static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags)
+{
+        return 0;
+}
+
+static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page*,
+                struct vm_area_struct *, unsigned long, void *), void *arg)
+{
+        return 0;
+}
+
+static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
+{
+}
 #endif /* !CONFIG_KSM */
 
-#endif
+#endif /* __LINUX_KSM_H */