1 files changed, 79 insertions, 0 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
new file mode 100644
index 000000000000..a485c14ecd5d
--- /dev/null
+++ b/include/linux/ksm.h
@@ -0,0 +1,79 @@
+#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/sched.h>
+#include <linux/vmstat.h>
+
+#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, with NULL anon_vma.
+ */
+static inline int PageKsm(struct page *page)
+{
+	return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
+}
+
+/*
+ * But we have to avoid the checking which page_add_anon_rmap() performs.
+ */
+static inline void page_add_ksm_rmap(struct page *page)
+{
+	if (atomic_inc_and_test(&page->_mapcount)) {
+		page->mapping = (void *) PAGE_MAPPING_ANON;
+		__inc_zone_page_state(page, NR_ANON_PAGES);
+	}
+}
+#else  /* !CONFIG_KSM */
+
+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_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;
+}
+
+/* No stub required for page_add_ksm_rmap(page) */
+#endif /* !CONFIG_KSM */
+
+#endif