1 files changed, 13 insertions, 1 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 02c09f3..d9c77b2 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;