1 files changed, 14 insertions, 0 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index a39b7b91be46..20a07dba6be0 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -11,6 +11,7 @@
 #include <linux/hugetlb.h>
 #include <linux/slab.h>
 #include <linux/shm.h>
+#include <linux/ksm.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
 #include <linux/capability.h>
@@ -174,6 +175,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
         unsigned long excess = 0;
         unsigned long hiwater_vm;
         int split = 0;
+        int err;
 
         /*
          * We'd prefer to avoid failure later on in do_munmap:
@@ -182,6 +184,18 @@ static unsigned long move_vma(struct vm_area_struct *vma,
         if (mm->map_count >= sysctl_max_map_count - 3)
                 return -ENOMEM;
 
+        /*
+         * Advise KSM to break any KSM pages in the area to be moved:
+         * it would be confusing if they were to turn up at the new
+         * location, where they happen to coincide with different KSM
+         * pages recently unmapped.  But leave vma->vm_flags as it was,
+         * so KSM can come around to merge on vma and new_vma afterwards.
+         */
+        err = ksm_madvise(vma, old_addr, old_addr + old_len,
+                                                MADV_UNMERGEABLE, &vm_flags);
+        if (err)
+                return err;
+
         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
         if (!new_vma)