drm/msm: Reference count address spaces

There are reasons for a memory object to outlive the file descriptor
that created it and so the address space that a buffer object is
attached to must also outlive the file descriptor. Reference count
the address space so that it can remain viable until all the objects
have released their addresses.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem.h

@@ -18,6 +18,7 @@
 #ifndef __MSM_GEM_H__
 #define __MSM_GEM_H__
 
+#include <linux/kref.h>
 #include <linux/reservation.h>
 #include "msm_drv.h"
 
@@ -31,6 +32,7 @@ struct msm_gem_address_space {
 	 */
 	struct drm_mm mm;
 	struct msm_mmu *mmu;
+	struct kref kref;
 };
 
 struct msm_gem_vma {