RE: [PATCHv3 5/7] tap: Extending tap device create/destroy APIs

-----Original Message-----
From: David Miller [mailto:davem@davemloft.net]
Sent: Tuesday, January 31, 2017 9:51 AM
To: Grandhi, Sainath <redacted>
Cc: <redacted>; <redacted>; linux-
kernel@vger.kernel.org
Subject: Re: [PATCHv3 5/7] tap: Extending tap device create/destroy APIs

From: Sainath Grandhi <redacted>
Date: Mon, 30 Jan 2017 11:12:00 -0800

quoted

+	list_for_each_entry_safe(tap_major, tmp, &major_list, next) {
+		if (tap_major->major == major) {
+			return tap_major;
+		}
+	}

Single line basic blocks, such as this 'if' statement, should not be surrounded
by curly braces.

Also I see not mutual exclusion being implemented to protect this list.  If there
is, it is not obvious, so it should be documented with a comment explaining
what protects the list.

Ok. It's my fault to not include safe reading of the list.
I would use the RCU API for list traversal, adding and deleting entries.
Please look for it in my next version.

quoted

@@ -1175,14 +1228,7 @@ int tap_create_cdev(struct cdev *tap_cdev,
 	if (err)
 		goto out2;

-	macvtap_major.major = MAJOR(*tap_major);
-
-	idr_init(&macvtap_major.minor_idr);
-	mutex_init(&macvtap_major.minor_lock);
-
-	macvtap_major.device_name = device_name;
-
-	return err;
+	return tap_list_add(*tap_major, device_name);

 out2:
 	unregister_chrdev_region(*tap_major, TAP_NUM_DEVS);

If tap_list_add() fails, you will leave the chrdev region registered.

Thanks. Would take care of it.