Re: [PATCH net-next RFC 2/2] tun: enable napi_gro_frags() for TUN/TAP driver

On Tue, 2017-09-05 at 15:35 -0700, Petar Penkov wrote:

Add a TUN/TAP receive mode that exercises the napi_gro_frags()
interface. This mode is available only in TAP mode, as the interface
expects packets with Ethernet headers.

Hi Petar, thanks a lot for this work.

I must confess I have to retract one feedback I gave while reviewing
your patches.

+		local_bh_disable();
+		data = napi_alloc_frag(fragsz);
+		local_bh_enable();
+		if (!data) {
+			err = -ENOMEM;
+			goto free;
+		}
+
+		page = virt_to_page(data);
+		offset = offset_in_page(data);

These two lines above indeed trigger too many problems in the kernel.
(Like the one you tried to cover here
https://patchwork.kernel.org/patch/9927927/ )

Please use for your next submission the code you originally had :

	page = virt_to_head_page(data);
	offset = data - page_address(page);


Thanks !