iscsi: dequeue all buffers from queue
PATCH 5/5 iscsi: dequeue all buffers from queue
debugged by [email protected]
patch and analysis by [email protected]
Only tcp_read_sock and recv_actor (iscsi_tcp_data_recv for us) see desc.count. It is is used just for permitting tcp_read_sock to read the portion of data in the socket.
When iscsi_tcp_data_recv sees a partial header, it sets desc.count. However, it is possible that the next skb (containing the rest of the header) still does not come. So I'm not sure that this scheme is completely correct.
Ideally, we should use the exact length of the data in the socket for desc.count. However, it is not so simple (see SIOCINQ in tcp_ioctl). So I think that iscsi_tcp_data_recv can just stop playing with desc.count and tell tcp_read_sock to read the all skbs. As proposed already, if iscsi_tcp_data_ready sets desc.count to non-zero, tcp_read_sock does that.
drivers/scsi/iscsi_tcp.c +8 -6
@@ -922,11 +922,8 @@ more: rc =iscsi_data_recv (conn);if (rc) { -if (rc == -EAGAIN ) { - rd_desc->count = tcp_conn->in.datalen - - tcp_conn->in.ctask->data_count; +if (rc == -EAGAIN ) goto again; - }iscsi_conn_failure (conn, rc);return 0 ; }
@@ -983,9 +980,14 @@ iscsi_tcp_data_ready(struct sock *sk, inread_lock (&sk->sk_callback_lock); -/* use rd_desc to pass 'conn' to iscsi_tcp_data_recv */ +/* +* Use rd_desc to pass 'conn' to iscsi_tcp_data_recv. +* We set count to 1 because we want the network layer to +* hand us all the skbs that are available. iscsi_tcp_data_recv +* handled pdus that cross buffers or pdus that still need data. +*/ rd_desc.arg.data = conn; - rd_desc.count =0 ; + rd_desc.count =1 ;tcp_read_sock (sk, &rd_desc, iscsi_tcp_data_recv);read_unlock (&sk->sk_callback_lock);