drm/i915: Track clients and print their object usage in debugfs

By stashing a pointer of who opened the device and keeping a list of
open fd, we can then walk each client and inspect how many objects they
have open. For example,

i915_gem_objects:
1102 objects, 613646336 bytes
663 [662] objects, 468783104 [468750336] bytes in gtt
  37 [37] active objects, 46874624 [46874624] bytes
  626 [625] inactive objects, 421908480 [421875712] bytes
282 unbound objects, 6512640 bytes
85 purgeable objects, 6787072 bytes
28 pinned mappable objects, 3686400 bytes
40 fault mappable objects, 27783168 bytes
2145386496 [536870912] gtt total

Xorg: 43 objects, 32243712 bytes (10223616 active, 16683008 inactive, 4096 unbound)
gnome-shell: 30 objects, 28381184 bytes (0 active, 28336128 inactive, 0 unbound)
xonotic-linux64: 1032 objects, 569933824 bytes (46874624 active, 383545344 inactive, 6508544 unbound)

v2: Use existing drm->filelist as pointed out by Ben.
v3: Not even stashing the task_struct is required as Ben pointed out
    drm_file->pid.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -196,6 +196,32 @@ static int i915_gem_object_list_info(struct seq_file *m, void *data)
 	} \
 } while (0)
 
+struct file_stats {
+	int count;
+	size_t total, active, inactive, unbound;
+};
+
+static int per_file_stats(int id, void *ptr, void *data)
+{
+	struct drm_i915_gem_object *obj = ptr;
+	struct file_stats *stats = data;
+
+	stats->count++;
+	stats->total += obj->base.size;
+
+	if (obj->gtt_space) {
+		if (!list_empty(&obj->ring_list))
+			stats->active += obj->base.size;
+		else
+			stats->inactive += obj->base.size;
+	} else {
+		if (!list_empty(&obj->global_list))
+			stats->unbound += obj->base.size;
+	}
+
+	return 0;
+}
+
 static int i915_gem_object_info(struct seq_file *m, void* data)
 {
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -204,6 +230,7 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 	u32 count, mappable_count, purgeable_count;
 	size_t size, mappable_size, purgeable_size;
 	struct drm_i915_gem_object *obj;
+	struct drm_file *file;
 	int ret;
 
 	ret = mutex_lock_interruptible(&dev->struct_mutex);
@@ -263,6 +290,21 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 		   dev_priv->gtt.total,
 		   dev_priv->gtt.mappable_end - dev_priv->gtt.start);
 
+	seq_printf(m, "\n");
+	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
+		struct file_stats stats;
+
+		memset(&stats, 0, sizeof(stats));
+		idr_for_each(&file->object_idr, per_file_stats, &stats);
+		seq_printf(m, "%s: %u objects, %zu bytes (%zu active, %zu inactive, %zu unbound)\n",
+			   get_pid_task(file->pid, PIDTYPE_PID)->comm,
+			   stats.count,
+			   stats.total,
+			   stats.active,
+			   stats.inactive,
+			   stats.unbound);
+	}
+
 	mutex_unlock(&dev->struct_mutex);
 
 	return 0;