1 files changed, 145 insertions, 0 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
new file mode 100644
index 000000000000..3319a6967626
--- /dev/null
+++ b/include/linux/ksm.h
@@ -0,0 +1,145 @@
+#ifndef __LINUX_KSM_H
+#define __LINUX_KSM_H
+/*
+ * Memory merging support.
+ *
+ * This code enables dynamic sharing of identical pages found in different
+ * memory areas, even if they are not shared by fork().
+ */
+
+#include <linux/bitops.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/sched.h>
+
+struct stable_node;
+struct mem_cgroup;
+
+struct page *ksm_does_need_to_copy(struct page *page,
+			struct vm_area_struct *vma, unsigned long address);
+
+#ifdef CONFIG_KSM
+int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end, int advice, unsigned long *vm_flags);
+int __ksm_enter(struct mm_struct *mm);
+void __ksm_exit(struct mm_struct *mm);
+
+static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
+		return __ksm_enter(mm);
+	return 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm)
+{
+	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		__ksm_exit(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, 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_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);
+}
+
+/*
+ * 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 int ksm_might_need_to_copy(struct page *page,
+			struct vm_area_struct *vma, unsigned long address)
+{
+	struct anon_vma *anon_vma = page_anon_vma(page);
+
+	return anon_vma &&
+		(anon_vma->root != vma->anon_vma->root ||
+		 page->index != linear_page_index(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_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+	return 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm)
+{
+}
+
+static inline int PageKsm(struct page *page)
+{
+	return 0;
+}
+
+#ifdef CONFIG_MMU
+static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end, int advice, unsigned long *vm_flags)
+{
+	return 0;
+}
+
+static inline int ksm_might_need_to_copy(struct page *page,
+			struct vm_area_struct *vma, unsigned long address)
+{
+	return 0;
+}
+
+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_MMU */
+#endif /* !CONFIG_KSM */
+
+#endif /* __LINUX_KSM_H */