drm/i915/gt: Fix memory leaks in per-gt sysfs

All kmalloc'd kobjects need a kobject_put() to free memory. For example in
previous code, kobj_gt_release() never gets called. The requirement of
kobject_put() now results in a slightly different code organization.

v2: s/gtn/gt/ (Andi)

Fixes: b770bcfa ("drm/i915/gt: create per-tile sysfs interface")
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a6f6686517c85fba61a0c45097f5bb4fe7e257fb.1653484574.git.ashutosh.dixit@intel.com

drivers/gpu/drm/i915/gt/intel_gt.c

@@ -790,6 +790,7 @@ void intel_gt_driver_unregister(struct intel_gt *gt)
 {
 	intel_wakeref_t wakeref;
 
+	intel_gt_sysfs_unregister(gt);
 	intel_rps_driver_unregister(&gt->rps);
 	intel_gsc_fini(&gt->gsc);
 

drivers/gpu/drm/i915/gt/intel_gt_sysfs.c

@@ -24,7 +24,7 @@ bool is_object_gt(struct kobject *kobj)
 
 static struct intel_gt *kobj_to_gt(struct kobject *kobj)
 {
-	return container_of(kobj, struct kobj_gt, base)->gt;
+	return container_of(kobj, struct intel_gt, sysfs_gt);
 }
 
 struct intel_gt *intel_gt_sysfs_get_drvdata(struct device *dev,
@@ -72,9 +72,9 @@ static struct attribute *id_attrs[] = {
 };
 ATTRIBUTE_GROUPS(id);
 
+/* A kobject needs a release() method even if it does nothing */
 static void kobj_gt_release(struct kobject *kobj)
 {
-	kfree(kobj);
 }
 
 static struct kobj_type kobj_gt_type = {
@@ -85,8 +85,6 @@ static struct kobj_type kobj_gt_type = {
 
 void intel_gt_sysfs_register(struct intel_gt *gt)
 {
-	struct kobj_gt *kg;
-
 	/*
 	 * We need to make things right with the
 	 * ABI compatibility. The files were originally
@@ -98,25 +96,22 @@ void intel_gt_sysfs_register(struct intel_gt *gt)
 	if (gt_is_root(gt))
 		intel_gt_sysfs_pm_init(gt, gt_get_parent_obj(gt));
 
-	kg = kzalloc(sizeof(*kg), GFP_KERNEL);
-	if (!kg)
+	/* init and xfer ownership to sysfs tree */
+	if (kobject_init_and_add(&gt->sysfs_gt, &kobj_gt_type,
+				 gt->i915->sysfs_gt, "gt%d", gt->info.id))
 		goto exit_fail;
 
-	kobject_init(&kg->base, &kobj_gt_type);
-	kg->gt = gt;
-
-	/* xfer ownership to sysfs tree */
-	if (kobject_add(&kg->base, gt->i915->sysfs_gt, "gt%d", gt->info.id))
-		goto exit_kobj_put;
-
-	intel_gt_sysfs_pm_init(gt, &kg->base);
+	intel_gt_sysfs_pm_init(gt, &gt->sysfs_gt);
 
 	return;
 
-exit_kobj_put:
-	kobject_put(&kg->base);
-
 exit_fail:
+	kobject_put(&gt->sysfs_gt);
 	drm_warn(&gt->i915->drm,
 		 "failed to initialize gt%d sysfs root\n", gt->info.id);
 }
+
+void intel_gt_sysfs_unregister(struct intel_gt *gt)
+{
+	kobject_put(&gt->sysfs_gt);
+}

drivers/gpu/drm/i915/gt/intel_gt_sysfs.h

@@ -13,11 +13,6 @@
 
 struct intel_gt;
 
-struct kobj_gt {
-	struct kobject base;
-	struct intel_gt *gt;
-};
-
 bool is_object_gt(struct kobject *kobj);
 
 struct drm_i915_private *kobj_to_i915(struct kobject *kobj);
@@ -28,6 +23,7 @@ intel_gt_create_kobj(struct intel_gt *gt,
 		     const char *name);
 
 void intel_gt_sysfs_register(struct intel_gt *gt);
+void intel_gt_sysfs_unregister(struct intel_gt *gt);
 struct intel_gt *intel_gt_sysfs_get_drvdata(struct device *dev,
 					    const char *name);
 

drivers/gpu/drm/i915/gt/intel_gt_types.h

@@ -225,6 +225,9 @@ struct intel_gt {
 	} mocs;
 
 	struct intel_pxp pxp;
+
+	/* gt/gtN sysfs */
+	struct kobject sysfs_gt;
 };
 
 enum intel_gt_scratch_field {

drivers/gpu/drm/i915/i915_sysfs.c

@@ -268,4 +268,6 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
 
 	device_remove_bin_file(kdev,  &dpf_attrs_1);
 	device_remove_bin_file(kdev,  &dpf_attrs);
+
+	kobject_put(dev_priv->sysfs_gt);
 }