[PATCH V3 08/15] scsi: iscsi: Run recv path from workqueue

[Mike Christie <michael.christie@oracle.com>]

We don't always want to run the recv path from the network softirq
because when we have to have multiple sessions sharing the same CPUs some
sessions can eat up the napi softirq budget and affect other sessions or
users. This patch allows us to queue the recv handling to the iscsi
workqueue so we can have the scheduler/wq code try to balance the work and
CPU use across all sessions's  worker threads.

Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/iscsi_tcp.c | 62 +++++++++++++++++++++++++++++++---------
 drivers/scsi/iscsi_tcp.h |  2 ++
 2 files changed, 51 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index c775acc5208d..dfca81d4e3ee 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -52,6 +52,10 @@ static struct iscsi_transport iscsi_sw_tcp_transport;
 static unsigned int iscsi_max_lun = ~0;
 module_param_named(max_lun, iscsi_max_lun, uint, S_IRUGO);
 
+static bool iscsi_recv_from_iscsi_q;
+module_param_named(recv_from_iscsi_q, iscsi_recv_from_iscsi_q, bool, 0644);
+MODULE_PARM_DESC(recv_from_iscsi_q, "Set to true to read iSCSI data/headers from the iscsi_q workqueue. The default is false which will perform reads from the network softirq context.");
+
 static int iscsi_sw_tcp_dbg;
 module_param_named(debug_iscsi_tcp, iscsi_sw_tcp_dbg, int,
 		   S_IRUGO | S_IWUSR);
@@ -122,20 +126,13 @@ static inline int iscsi_sw_sk_state_check(struct sock *sk)
 	return 0;
 }
 
-static void iscsi_sw_tcp_data_ready(struct sock *sk)
+static void iscsi_sw_tcp_recv_data(struct iscsi_conn *conn)
 {
-	struct iscsi_conn *conn;
-	struct iscsi_tcp_conn *tcp_conn;
+	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
+	struct sock *sk = tcp_sw_conn->sock->sk;
 	read_descriptor_t rd_desc;
 
-	read_lock_bh(&sk->sk_callback_lock);
-	conn = sk->sk_user_data;
-	if (!conn) {
-		read_unlock_bh(&sk->sk_callback_lock);
-		return;
-	}
-	tcp_conn = conn->dd_data;
-
 	/*
 	 * Use rd_desc to pass 'conn' to iscsi_tcp_recv.
 	 * We set count to 1 because we want the network layer to
@@ -144,13 +141,48 @@ static void iscsi_sw_tcp_data_ready(struct sock *sk)
 	 */
 	rd_desc.arg.data = conn;
 	rd_desc.count = 1;
-	tcp_read_sock(sk, &rd_desc, iscsi_sw_tcp_recv);
 
-	iscsi_sw_sk_state_check(sk);
+	tcp_read_sock(sk, &rd_desc, iscsi_sw_tcp_recv);
 
 	/* If we had to (atomically) map a highmem page,
 	 * unmap it now. */
 	iscsi_tcp_segment_unmap(&tcp_conn->in.segment);
+
+	iscsi_sw_sk_state_check(sk);
+}
+
+static void iscsi_sw_tcp_recv_data_work(struct work_struct *work)
+{
+	struct iscsi_conn *conn = container_of(work, struct iscsi_conn,
+					       recvwork);
+	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
+	struct sock *sk = tcp_sw_conn->sock->sk;
+
+	lock_sock(sk);
+	iscsi_sw_tcp_recv_data(conn);
+	release_sock(sk);
+}
+
+static void iscsi_sw_tcp_data_ready(struct sock *sk)
+{
+	struct iscsi_sw_tcp_conn *tcp_sw_conn;
+	struct iscsi_tcp_conn *tcp_conn;
+	struct iscsi_conn *conn;
+
+	read_lock_bh(&sk->sk_callback_lock);
+	conn = sk->sk_user_data;
+	if (!conn) {
+		read_unlock_bh(&sk->sk_callback_lock);
+		return;
+	}
+	tcp_conn = conn->dd_data;
+	tcp_sw_conn = tcp_conn->dd_data;
+
+	if (tcp_sw_conn->queue_recv)
+		iscsi_conn_queue_recv(conn);
+	else
+		iscsi_sw_tcp_recv_data(conn);
 	read_unlock_bh(&sk->sk_callback_lock);
 }
 
@@ -557,6 +589,8 @@ iscsi_sw_tcp_conn_create(struct iscsi_cls_session *cls_session,
 	conn = cls_conn->dd_data;
 	tcp_conn = conn->dd_data;
 	tcp_sw_conn = tcp_conn->dd_data;
+	INIT_WORK(&conn->recvwork, iscsi_sw_tcp_recv_data_work);
+	tcp_sw_conn->queue_recv = iscsi_recv_from_iscsi_q;
 
 	tfm = crypto_alloc_ahash("crc32c", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(tfm))
@@ -610,6 +644,8 @@ static void iscsi_sw_tcp_release_conn(struct iscsi_conn *conn)
 	iscsi_sw_tcp_conn_restore_callbacks(conn);
 	sock_put(sock->sk);
 
+	iscsi_suspend_rx(conn);
+
 	spin_lock_bh(&session->frwd_lock);
 	tcp_sw_conn->sock = NULL;
 	spin_unlock_bh(&session->frwd_lock);
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 791453195099..850a018aefb9 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -28,6 +28,8 @@ struct iscsi_sw_tcp_send {
 
 struct iscsi_sw_tcp_conn {
 	struct socket		*sock;
+	struct work_struct	recvwork;
+	bool			queue_recv;
 
 	struct iscsi_sw_tcp_send out;
 	/* old values for socket callbacks */
-- 
2.25.1