[PATCH] drm: make sure page protections are updated after changing vm_flags.

[Jeremy Fitzhardinge <jeremy@goop.org>]

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>

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 8104eca..9d3e39f 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -537,7 +537,7 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_ops = obj->dev->driver->gem_vm_ops;
 	vma->vm_private_data = map->handle;
 	/* FIXME: use pgprot_writecombine when available */
-	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.