Some architectures compute ->vm_page_prot depending on ->vm_flags, so we

need to update the protections after adjusting the flags.
Reported-by: Jan Beulich <JBeulich@novell.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/gpu/drm/drm_gem.c

@@ -552,7 +552,7 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_flags |= VM_RESERVED | VM_IO | VM_PFNMAP | VM_DONTEXPAND;
 	vma->vm_ops = obj->dev->driver->gem_vm_ops;
 	vma->vm_private_data = map->handle;
-	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+	vma->vm_page_prot =  pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
 
 	/* Take a ref for this mapping of the object, so that the fault
 	 * handler can dereference the mmap offset's pointer to the object.