drm/i915: Allow shrinking of userptr objects once again

Commit 1bec9b0b ("drm/i915/shrinker: Only shmemfs objects
are backed by swap") stopped considering the userptr objects
in shrinker callbacks.

Restore that so idle userptr objects can be discarded in order
to free up memory.

One change further to what was introduced in 1bec9b0b is
to start considering userptr objects in oom but that should
also be a correct thing to do.

v2: Introduce I915_GEM_OBJECT_IS_SHRINKABLE. (Chris Wilson)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 1bec9b0b ("drm/i915/shrinker: Only shmemfs objects are backed by swap")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: <stable@vger.kernel.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1478011450-6634-1-git-send-email-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -2181,6 +2181,7 @@ enum hdmi_force_audio {
 struct drm_i915_gem_object_ops {
 	unsigned int flags;
 #define I915_GEM_OBJECT_HAS_STRUCT_PAGE 0x1
+#define I915_GEM_OBJECT_IS_SHRINKABLE   0x2
 
 	/* Interface between the GEM object and its backing storage.
 	 * get_pages() is called once prior to the use of the associated set
@@ -2429,6 +2430,12 @@ i915_gem_object_has_struct_page(const struct drm_i915_gem_object *obj)
 	return obj->ops->flags & I915_GEM_OBJECT_HAS_STRUCT_PAGE;
 }
 
+static inline bool
+i915_gem_object_is_shrinkable(const struct drm_i915_gem_object *obj)
+{
+	return obj->ops->flags & I915_GEM_OBJECT_IS_SHRINKABLE;
+}
+
 static inline bool
 i915_gem_object_is_active(const struct drm_i915_gem_object *obj)
 {

drivers/gpu/drm/i915/i915_gem.c

@@ -4146,7 +4146,8 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_object_ops = {
-	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
+		 I915_GEM_OBJECT_IS_SHRINKABLE,
 	.get_pages = i915_gem_object_get_pages_gtt,
 	.put_pages = i915_gem_object_put_pages_gtt,
 };

drivers/gpu/drm/i915/i915_gem_internal.c

@@ -132,7 +132,8 @@ static void i915_gem_object_put_pages_internal(struct drm_i915_gem_object *obj,
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_object_internal_ops = {
-	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
+		 I915_GEM_OBJECT_IS_SHRINKABLE,
 	.get_pages = i915_gem_object_get_pages_internal,
 	.put_pages = i915_gem_object_put_pages_internal,
 };

drivers/gpu/drm/i915/i915_gem_shrinker.c

@@ -83,8 +83,8 @@ static bool can_release_pages(struct drm_i915_gem_object *obj)
 	if (!obj->mm.pages)
 		return false;
 
-	/* Only shmemfs objects are backed by swap */
-	if (!obj->base.filp)
+	/* Consider only shrinkable ojects. */
+	if (!i915_gem_object_is_shrinkable(obj))
 		return false;
 
 	/* Only report true if by unbinding the object and putting its pages

drivers/gpu/drm/i915/i915_gem_userptr.c

@@ -707,7 +707,8 @@ i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj)
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
-	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE,
+	.flags = I915_GEM_OBJECT_HAS_STRUCT_PAGE |
+		 I915_GEM_OBJECT_IS_SHRINKABLE,
 	.get_pages = i915_gem_userptr_get_pages,
 	.put_pages = i915_gem_userptr_put_pages,
 	.dmabuf_export = i915_gem_userptr_dmabuf_export,