2 files changed, 53 insertions, 6 deletions

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index ef55ce14a2ce..157d83dbaef8 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -9,10 +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,
@@ -57,11 +59,36 @@ static inline void set_page_stable_node(struct page *page,
                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
 }
 
-static inline void page_add_ksm_rmap(struct page *page)
+/*
+ * 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?
+ */
+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))
-                __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);
+
 #else  /* !CONFIG_KSM */
 
 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -84,7 +111,22 @@ 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;
+}
 #endif /* !CONFIG_KSM */
 
-#endif
+#endif /* __LINUX_KSM_H */
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 1f65af44c6d2..0b4913a4a344 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -89,6 +89,9 @@ static inline void page_dup_rmap(struct page *page)
  */
 int page_referenced(struct page *, int is_locked,
                         struct mem_cgroup *cnt, unsigned long *vm_flags);
+int page_referenced_one(struct page *, struct vm_area_struct *,
+        unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
+
 enum ttu_flags {
         TTU_UNMAP = 0,                  /* unmap mode */
         TTU_MIGRATION = 1,              /* migration mode */
@@ -102,6 +105,8 @@ enum ttu_flags {
 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 
 int try_to_unmap(struct page *, enum ttu_flags flags);
+int try_to_unmap_one(struct page *, struct vm_area_struct *,
+                        unsigned long address, enum ttu_flags flags);
 
 /*
  * Called from mm/filemap_xip.c to unmap empty zero page