drm/i915: Sanitize GEM shrinker init and clean-up

Factor out the common GEM shrinker clean-up code and call the shrinker
init function from the same function from where the corresponding
shrinker clean-up function is called. Also add sanity checking to the
shrinker and OOM registration calls.
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: David Weinehall <david.weinehall@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453209992-25995-4-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_dma.c

@@ -1035,6 +1035,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	intel_opregion_setup(dev);
 
 	i915_gem_load(dev);
+	i915_gem_shrinker_init(dev_priv);
 
 	/* On the 945G/GM, the chipset reports the MSI capability on the
 	 * integrated graphics even though the support isn't actually there
@@ -1098,8 +1099,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	intel_power_domains_fini(dev_priv);
 	drm_vblank_cleanup(dev);
 out_gem_unload:
-	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
-	unregister_shrinker(&dev_priv->mm.shrinker);
+	i915_gem_shrinker_cleanup(dev_priv);
 
 	if (dev->pdev->msi_enabled)
 		pci_disable_msi(dev->pdev);
@@ -1152,8 +1152,7 @@ int i915_driver_unload(struct drm_device *dev)
 
 	i915_teardown_sysfs(dev);
 
-	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
-	unregister_shrinker(&dev_priv->mm.shrinker);
+	i915_gem_shrinker_cleanup(dev_priv);
 
 	io_mapping_free(dev_priv->gtt.mappable);
 	arch_phys_wc_del(dev_priv->gtt.mtrr);

drivers/gpu/drm/i915/i915_drv.h

@@ -3261,6 +3261,7 @@ unsigned long i915_gem_shrink(struct drm_i915_private *dev_priv,
 #define I915_SHRINK_ACTIVE 0x8
 unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv);
 void i915_gem_shrinker_init(struct drm_i915_private *dev_priv);
+void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv);
 
 
 /* i915_gem_tiling.c */

drivers/gpu/drm/i915/i915_gem.c

@@ -5100,8 +5100,6 @@ i915_gem_load(struct drm_device *dev)
 
 	dev_priv->mm.interruptible = true;
 
-	i915_gem_shrinker_init(dev_priv);
-
 	mutex_init(&dev_priv->fb_tracking.lock);
 }
 

drivers/gpu/drm/i915/i915_gem_shrinker.c

@@ -367,8 +367,20 @@ void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
 	dev_priv->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 	dev_priv->mm.shrinker.count_objects = i915_gem_shrinker_count;
 	dev_priv->mm.shrinker.seeks = DEFAULT_SEEKS;
-	register_shrinker(&dev_priv->mm.shrinker);
+	WARN_ON(register_shrinker(&dev_priv->mm.shrinker));
 
 	dev_priv->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
-	register_oom_notifier(&dev_priv->mm.oom_notifier);
+	WARN_ON(register_oom_notifier(&dev_priv->mm.oom_notifier));
+}
+
+/**
+ * i915_gem_shrinker_cleanup - Clean up i915 shrinker
+ * @dev_priv: i915 device
+ *
+ * This function unregisters the i915 shrinker and OOM handler.
+ */
+void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv)
+{
+	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
+	unregister_shrinker(&dev_priv->mm.shrinker);
 }