iscsi-target: Convert iscsi_session statistics to atomic_long_t

This patch converts a handful of iscsi_session statistics to type
atomic_long_t, instead of using iscsi_session->session_stats_lock
when incrementing these values.

More importantly, go ahead and drop the spinlock usage within
iscsit_setup_scsi_cmd(), iscsit_check_dataout_hdr(),
iscsit_send_datain(), and iscsit_build_rsp_pdu() fast-path code.

(Squash in Roland's target: Remove write-only stats fields and lock
from struct se_node_acl)

Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/iscsi/iscsi_target.c

···
 	int iscsi_task_attr;
 	int sam_task_attr;
 
-	spin_lock_bh(&conn->sess->session_stats_lock);
-	conn->sess->cmd_pdus++;
-	if (conn->sess->se_sess->se_node_acl) {
-		spin_lock(&conn->sess->se_sess->se_node_acl->stats_lock);
-		conn->sess->se_sess->se_node_acl->num_cmds++;
-		spin_unlock(&conn->sess->se_sess->se_node_acl->stats_lock);
-	}
-	spin_unlock_bh(&conn->sess->session_stats_lock);
+	atomic_long_inc(&conn->sess->cmd_pdus);
 
 	hdr			= (struct iscsi_scsi_req *) buf;
 	payload_length		= ntoh24(hdr->dlength);
···
 	}
 
 	/* iSCSI write */
-	spin_lock_bh(&conn->sess->session_stats_lock);
-	conn->sess->rx_data_octets += payload_length;
-	if (conn->sess->se_sess->se_node_acl) {
-		spin_lock(&conn->sess->se_sess->se_node_acl->stats_lock);
-		conn->sess->se_sess->se_node_acl->write_bytes += payload_length;
-		spin_unlock(&conn->sess->se_sess->se_node_acl->stats_lock);
-	}
-	spin_unlock_bh(&conn->sess->session_stats_lock);
+	atomic_long_add(payload_length, &conn->sess->rx_data_octets);
 
 	if (payload_length > conn->conn_ops->MaxXmitDataSegmentLength) {
 		pr_err("DataSegmentLength: %u is greater than"
···
 		return -1;
 	}
 
-	spin_lock_bh(&conn->sess->session_stats_lock);
-	conn->sess->tx_data_octets += datain.length;
-	if (conn->sess->se_sess->se_node_acl) {
-		spin_lock(&conn->sess->se_sess->se_node_acl->stats_lock);
-		conn->sess->se_sess->se_node_acl->read_bytes += datain.length;
-		spin_unlock(&conn->sess->se_sess->se_node_acl->stats_lock);
-	}
-	spin_unlock_bh(&conn->sess->session_stats_lock);
+	atomic_long_add(datain.length, &conn->sess->tx_data_octets);
 	/*
 	 * Special case for successfully execution w/ both DATAIN
 	 * and Sense Data.
···
 	if (inc_stat_sn)
 		cmd->stat_sn = conn->stat_sn++;
 
-	spin_lock_bh(&conn->sess->session_stats_lock);
-	conn->sess->rsp_pdus++;
-	spin_unlock_bh(&conn->sess->session_stats_lock);
+	atomic_long_inc(&conn->sess->rsp_pdus);
 
 	memset(hdr, 0, ISCSI_HDR_LEN);
 	hdr->opcode		= ISCSI_OP_SCSI_CMD_RSP;
···
 				 * hit default in the switch below.
 				 */
 				memset(buffer, 0xff, ISCSI_HDR_LEN);
-				spin_lock_bh(&conn->sess->session_stats_lock);
-				conn->sess->conn_digest_errors++;
-				spin_unlock_bh(&conn->sess->session_stats_lock);
+				atomic_long_inc(&conn->sess->conn_digest_errors);
 			} else {
 				pr_debug("Got HeaderDigest CRC32C"
 						" 0x%08x\n", checksum);

drivers/target/iscsi/iscsi_target_core.h

···
 	/* Used for session reference counting */
 	int			session_usage_count;
 	int			session_waiting_on_uc;
-	u32			cmd_pdus;
-	u32			rsp_pdus;
-	u64			tx_data_octets;
-	u64			rx_data_octets;
-	u32			conn_digest_errors;
-	u32			conn_timeout_errors;
+	atomic_long_t		cmd_pdus;
+	atomic_long_t		rsp_pdus;
+	atomic_long_t		tx_data_octets;
+	atomic_long_t		rx_data_octets;
+	atomic_long_t		conn_digest_errors;
+	atomic_long_t		conn_timeout_errors;
 	u64			creation_time;
-	spinlock_t		session_stats_lock;
 	/* Number of active connections */
 	atomic_t		nconn;
 	atomic_t		session_continuation;

drivers/target/iscsi/iscsi_target_erl0.c

···
 		tiqn->sess_err_stats.last_sess_failure_type =
 				ISCSI_SESS_ERR_CXN_TIMEOUT;
 		tiqn->sess_err_stats.cxn_timeout_errors++;
-		sess->conn_timeout_errors++;
+		atomic_long_inc(&sess->conn_timeout_errors);
 		spin_unlock(&tiqn->sess_err_stats.lock);
 	}
 	}

drivers/target/iscsi/iscsi_target_login.c

···
 	}
 
 	sess->creation_time = get_jiffies_64();
-	spin_lock_init(&sess->session_stats_lock);
 	/*
 	 * The FFP CmdSN window values will be allocated from the TPG's
 	 * Initiator Node's ACL once the login has been successfully completed.

drivers/target/iscsi/iscsi_target_stat.c

···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%u\n", sess->cmd_pdus);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->cmd_pdus));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 
···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%u\n", sess->rsp_pdus);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->rsp_pdus));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 
···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%llu\n",
-				(unsigned long long)sess->tx_data_octets);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->tx_data_octets));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 
···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%llu\n",
-				(unsigned long long)sess->rx_data_octets);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->rx_data_octets));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 
···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%u\n",
-					sess->conn_digest_errors);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->conn_digest_errors));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 
···
 	if (se_sess) {
 		sess = se_sess->fabric_sess_ptr;
 		if (sess)
-			ret = snprintf(page, PAGE_SIZE, "%u\n",
-					sess->conn_timeout_errors);
+			ret = snprintf(page, PAGE_SIZE, "%lu\n",
+				       atomic_long_read(&sess->conn_timeout_errors));
 	}
 	spin_unlock_bh(&se_nacl->nacl_sess_lock);
 

drivers/target/iscsi/iscsi_target_util.c

···
 		tiqn->sess_err_stats.last_sess_failure_type =
 				ISCSI_SESS_ERR_CXN_TIMEOUT;
 		tiqn->sess_err_stats.cxn_timeout_errors++;
-		conn->sess->conn_timeout_errors++;
+		atomic_long_inc(&conn->sess->conn_timeout_errors);
 		spin_unlock_bh(&tiqn->sess_err_stats.lock);
 	}
 	}