1 files changed, 56 insertions, 0 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
new file mode 100644
index 000000000000..8b76008fcd32
--- /dev/null
+++ b/mm/ksm.c
@@ -0,0 +1,56 @@
+/*
+ * Initial dummy version just to illustrate KSM's interface to other files.
+ */
+
+#include <linux/errno.h>
+#include <linux/mman.h>
+#include <linux/ksm.h>
+
+int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
+		unsigned long end, int advice, unsigned long *vm_flags)
+{
+	struct mm_struct *mm = vma->vm_mm;
+
+	switch (advice) {
+	case MADV_MERGEABLE:
+		/*
+		 * Be somewhat over-protective for now!
+		 */
+		if (*vm_flags & (VM_MERGEABLE | VM_SHARED  | VM_MAYSHARE   |
+				 VM_PFNMAP    | VM_IO      | VM_DONTEXPAND |
+				 VM_RESERVED  | VM_HUGETLB | VM_INSERTPAGE |
+				 VM_MIXEDMAP  | VM_SAO))
+			return 0;		/* just ignore the advice */
+
+		if (!test_bit(MMF_VM_MERGEABLE, &mm->flags))
+			if (__ksm_enter(mm) < 0)
+				return -EAGAIN;
+
+		*vm_flags |= VM_MERGEABLE;
+		break;
+
+	case MADV_UNMERGEABLE:
+		if (!(*vm_flags & VM_MERGEABLE))
+			return 0;		/* just ignore the advice */
+
+		/* Unmerge any merged pages here */
+
+		*vm_flags &= ~VM_MERGEABLE;
+		break;
+	}
+
+	return 0;
+}
+
+int __ksm_enter(struct mm_struct *mm)
+{
+	/* Allocate a structure to track mm and link it into KSM's list */
+	set_bit(MMF_VM_MERGEABLE, &mm->flags);
+	return 0;
+}
+
+void __ksm_exit(struct mm_struct *mm)
+{
+	/* Unlink and free all KSM's structures which track this mm */
+	clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+}