staging: ion: Make sure all clients are exposed in debugfs

Currently, if multiple Ion clients are created with the same name, only
the first one shows up in debugfs. Rectify this by adding a
monotonically-increasing serial number to the debug names of Ion
clients.

Cc: Colin Cross <[e-mail]>
Cc: Android Kernel Team <[e-mail]>
Signed-off-by: Mitchel Humpherys <[e-mail]>
[jstultz: Minor commit subject tweaks]
Signed-off-by: John Stultz <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/android/ion/ion.c

···
  * @idr:		an idr space for allocating handle ids
  * @lock:		lock protecting the tree of handles
  * @name:		used for debugging
+ * @display_name:	used for debugging (unique version of @name)
+ * @display_serial:	used for debugging (to make display_name unique)
  * @task:		used for debugging
  *
  * A client represents a list of buffers this client may access.
···
 	struct idr idr;
 	struct mutex lock;
 	const char *name;
+	char *display_name;
+	int display_serial;
 	struct task_struct *task;
 	pid_t pid;
 	struct dentry *debug_root;
···
 	.release = single_release,
 };
 
+static int ion_get_client_serial(const struct rb_root *root,
+					const unsigned char *name)
+{
+	int serial = -1;
+	struct rb_node *node;
+	for (node = rb_first(root); node; node = rb_next(node)) {
+		struct ion_client *client = rb_entry(node, struct ion_client,
+						node);
+		if (strcmp(client->name, name))
+			continue;
+		serial = max(serial, client->display_serial);
+	}
+	return serial + 1;
+}
+
 struct ion_client *ion_client_create(struct ion_device *dev,
 				     const char *name)
 {
···
 	struct rb_node *parent = NULL;
 	struct ion_client *entry;
 	pid_t pid;
+
+	if (!name) {
+		pr_err("%s: Name cannot be null\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
 
 	get_task_struct(current->group_leader);
 	task_lock(current->group_leader);
···
 		goto err_free_client;
 
 	down_write(&dev->lock);
+	client->display_serial = ion_get_client_serial(&dev->clients, name);
+	client->display_name = kasprintf(
+		GFP_KERNEL, "%s-%d", name, client->display_serial);
+	if (!client->display_name) {
+		up_write(&dev->lock);
+		goto err_free_client_name;
+	}
 	p = &dev->clients.rb_node;
 	while (*p) {
 		parent = *p;
···
 	rb_link_node(&client->node, parent, p);
 	rb_insert_color(&client->node, &dev->clients);
 
-	client->debug_root = debugfs_create_file(name, 0664,
+	client->debug_root = debugfs_create_file(client->display_name, 0664,
 						dev->clients_debug_root,
 						client, &debug_client_fops);
 	if (!client->debug_root) {
 		char buf[256], *path;
 		path = dentry_path(dev->clients_debug_root, buf, 256);
 		pr_err("Failed to create client debugfs at %s/%s\n",
-			path, name);
+			path, client->display_name);
 	}
 
 	up_write(&dev->lock);
 
 	return client;
 
+err_free_client_name:
+	kfree(client->name);
 err_free_client:
 	kfree(client);
 err_put_task_struct:
···
 	debugfs_remove_recursive(client->debug_root);
 	up_write(&dev->lock);
 
+	kfree(client->display_name);
 	kfree(client->name);
 	kfree(client);
 }