1 files changed, 13 insertions, 1 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 02c09f33df8b..d9c77b2dbe9d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1198,8 +1198,20 @@ munmap_back:
                         goto free_vma;
         }
 
-        if (vma_wants_writenotify(vma))
+        if (vma_wants_writenotify(vma)) {
+                pgprot_t pprot = vma->vm_page_prot;
+
+                /* Can vma->vm_page_prot have changed??
+                 *
+                 * Answer: Yes, drivers may have changed it in their
+                 *         f_op->mmap method.
+                 *
+                 * Ensures that vmas marked as uncached stay that way.
+                 */
                 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
+                if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
+                        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+        }
 
         vma_link(mm, vma, prev, rb_link, rb_parent);
         file = vma->vm_file;