Re: [PATCH 2/3] Bluetooth: Handle fragmented skbs in bt_sock_stream_recvmsg()

[Mat Martineau <mathewm@codeaurora.org>]

Hi Gustavo -

On Fri, 22 Jul 2011, Gustavo Padovan wrote:

> * Mat Martineau <mathewm@codeaurora.org> [2011-07-13 10:58:38 -0700]:
>
>> ERTM reassembly will be more efficient when skbs are linked together
>> rather than copying every incoming data byte. The existing stream recv
>> function assumes skbs are linear, so it needs to know how to handle
>> fragments before reassembly is changed.
>>
>> bt_sock_recvmsg() already handles fragmented skbs.
>>
>> Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
>> ---
>>  net/bluetooth/af_bluetooth.c |   30 ++++++++++++++++++++++++++++--
>>  1 files changed, 28 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
>> index 8add9b4..9a43520 100644
>> --- a/net/bluetooth/af_bluetooth.c
>> +++ b/net/bluetooth/af_bluetooth.c
>> @@ -349,7 +349,7 @@ int bt_sock_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
>>  		}
>>
>>  		chunk = min_t(unsigned int, skb->len, size);
>> -		if (memcpy_toiovec(msg->msg_iov, skb->data, chunk)) {
>> +		if (skb_copy_datagram_iovec(skb, 0, msg->msg_iov, chunk)) {
>>  			skb_queue_head(&sk->sk_receive_queue, skb);
>>  			if (!copied)
>>  				copied = -EFAULT;
>> @@ -361,7 +361,33 @@ int bt_sock_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
>>  		sock_recv_ts_and_drops(msg, sk, skb);
>>
>>  		if (!(flags & MSG_PEEK)) {
>> -			skb_pull(skb, chunk);
>> +			int skb_len = skb_headlen(skb);
>> +
>> +			if (chunk <= skb_len) {
>> +				__skb_pull(skb, chunk);
>> +			} else {
>> +				struct sk_buff *frag;
>> +
>> +				__skb_pull(skb, skb_len);
>> +				chunk -= skb_len;
>> +
>> +				skb_walk_frags(skb, frag) {
>> +					if (chunk <= frag->len) {
>> +						/* Pulling partial data */
>> +						skb->len -= chunk;
>> +						skb->data_len -= chunk;
>> +						__skb_pull(frag, chunk);
>> +						break;
>> +					} else if (frag->len) {
>> +						/* Pulling all frag data */
>> +						chunk -= frag->len;
>> +						skb->len -= frag->len;
>> +						skb->data_len -= frag->len;
>> +						__skb_pull(frag, frag->len);
>> +					}
>> +				}
>> +			}
>> +
>
> ERTM and Streaming mode can also use SOCK_SEQPACKET, I think you also need to
> handle this for SOCK_SEQPACKET.

bt_sock_recvmsg() is used with SOCK_SEQPACKET, and it already handles 
fragmented skbs without any changes.  See skb_copy_datagram_iovec(), 
which is called by bt_sock_recvmsg() to copy the data out of the skb.


--
Mat Martineau
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum