iSCSI: Fast and per-session timeouts

Support per-session configurable ping (SCSI NOP) and login timeouts
similar to what is supported in the Linux iSCSI initiator configuration file.

Reduce iscsi timer granularity to 0.1 sec.
For backwards compatibility, when all timers are selected on integer numbers,
all status messages are unchanged. If the higher granularity is used, the
log messages include sub-second granularity.

The sysctl(3) interface has changed from pure int to string, in order to
support fractional seconds in a human-readable, dotted notation.

Reviewed By: #netapp, #manpages, jhb, pauamma_chezdork.com, siderop1_netapp.com
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D32540

sys/dev/iscsi/iscsi.c

@@ -104,15 +104,15 @@ static int debug = 1;
 SYSCTL_INT(_kern_iscsi, OID_AUTO, debug, CTLFLAG_RWTUN,
     &debug, 0, "Enable debug messages");
 
-static int ping_timeout = 5;
+static int ping_timeout = 5000;
 SYSCTL_INT(_kern_iscsi, OID_AUTO, ping_timeout, CTLFLAG_RWTUN, &ping_timeout,
-    0, "Timeout for ping (NOP-Out) requests, in seconds");
-static int iscsid_timeout = 60;
+    0, "Timeout for ping (NOP-Out) requests, in milliseconds");
+static int iscsid_timeout = 60000;
 SYSCTL_INT(_kern_iscsi, OID_AUTO, iscsid_timeout, CTLFLAG_RWTUN, &iscsid_timeout,
-    0, "Time to wait for iscsid(8) to handle reconnection, in seconds");
-static int login_timeout = 60;
+    0, "Time to wait for iscsid(8) to handle reconnection, in milliseconds");
+static int login_timeout = 60000;
 SYSCTL_INT(_kern_iscsi, OID_AUTO, login_timeout, CTLFLAG_RWTUN, &login_timeout,
-    0, "Time to wait for iscsid(8) to finish Login Phase, in seconds");
+    0, "Time to wait for iscsid(8) to finish Login Phase, in milliseconds");
 static int maxtags = 255;
 SYSCTL_INT(_kern_iscsi, OID_AUTO, maxtags, CTLFLAG_RWTUN, &maxtags,
     0, "Max number of IO requests queued");
@@ -585,6 +585,8 @@ iscsi_callout(void *context)
 	struct iscsi_session *is;
 	bool reconnect_needed = false;
 	sbintime_t sbt, pr;
+	bool fast_timer = false;
+	char tmpstr[5];
 
 	is = context;
 
@@ -594,29 +596,38 @@ iscsi_callout(void *context)
 		return;
 	}
 
-	sbt = mstosbt(995);
+	fast_timer = ((is->is_ping_timeout <= 2000) ||
+			(is->is_login_timeout <= 2000));
+	sbt = mstosbt(fast_timer ? 95 : 995);
 	pr  = mstosbt(10);
 	callout_schedule_sbt(&is->is_callout, sbt, pr, 0);
 
 	if (is->is_conf.isc_enable == 0)
 		goto out;
 
-	is->is_timeout++;
+	is->is_timeout += (fast_timer ? 100 : 1000);
 
+	tmpstr[0] = '\0';
 	if (is->is_waiting_for_iscsid) {
-		if (iscsid_timeout > 0 && is->is_timeout > iscsid_timeout) {
+		if (iscsid_timeout > 0 && is->is_timeout >= iscsid_timeout) {
+			if (fast_timer && ((is->is_timeout % 1000) != 0))
+				snprintf(tmpstr, sizeof(tmpstr), ".%d",
+					(is->is_timeout % 1000) / 100);
 			ISCSI_SESSION_WARN(is, "timed out waiting for iscsid(8) "
-			    "for %d seconds; reconnecting",
-			    is->is_timeout);
+			    "for %d%s seconds; reconnecting",
+			    is->is_timeout / 1000, tmpstr);
 			reconnect_needed = true;
 		}
 		goto out;
 	}
 
 	if (is->is_login_phase) {
-		if (is->is_login_timeout > 0 && is->is_timeout > is->is_login_timeout) {
-			ISCSI_SESSION_WARN(is, "login timed out after %d seconds; "
-			    "reconnecting", is->is_timeout);
+		if (is->is_login_timeout > 0 && is->is_timeout >= is->is_login_timeout) {
+			if (fast_timer && ((is->is_timeout % 1000) != 0))
+				snprintf(tmpstr, sizeof(tmpstr), ".%d",
+					(is->is_timeout % 1000) / 100);
+			ISCSI_SESSION_WARN(is, "login timed out after %d%s seconds; "
+			    "reconnecting", is->is_timeout / 1000, tmpstr);
 			reconnect_needed = true;
 		}
 		goto out;
@@ -633,8 +644,11 @@ iscsi_callout(void *context)
 	}
 
 	if (is->is_timeout >= is->is_ping_timeout) {
-		ISCSI_SESSION_WARN(is, "no ping reply (NOP-In) after %d seconds; "
-		    "reconnecting", is->is_ping_timeout);
+		if (fast_timer && ((is->is_timeout % 1000) != 0))
+			snprintf(tmpstr, sizeof(tmpstr), ".%d",
+				(is->is_timeout % 1000) / 100);
+		ISCSI_SESSION_WARN(is, "no ping reply (NOP-In) after %d%s seconds; "
+		    "reconnecting", is->is_timeout / 1000, tmpstr);
 		reconnect_needed = true;
 		goto out;
 	}
@@ -649,7 +663,7 @@ iscsi_callout(void *context)
 	 * (It's 2 - one for one second, and one for incrementing is_timeout
 	 * earlier in this routine.)
 	 */
-	if (is->is_timeout < 2)
+	if (is->is_timeout < (fast_timer ? 200 : 2000))
 		return;
 
 	request = icl_pdu_new(is->is_conn, M_NOWAIT);
@@ -1965,6 +1979,7 @@ iscsi_ioctl_session_add(struct iscsi_softc *sc, struct iscsi_session_add *isa)
 	const struct iscsi_session *is2;
 	int error;
 	sbintime_t sbt, pr;
+	bool fast_timer;
 
 	iscsi_sanitize_session_conf(&isa->isa_conf);
 	if (iscsi_valid_session_conf(&isa->isa_conf) == false)
@@ -2048,7 +2063,9 @@ iscsi_ioctl_session_add(struct iscsi_softc *sc, struct iscsi_session_add *isa)
 	if (is->is_login_timeout < 0)
 		is->is_login_timeout = login_timeout;
 
-	sbt = mstosbt(995);
+	fast_timer = ((is->is_ping_timeout <= 2000) ||
+			(is->is_ping_timeout <= 2000));
+	sbt = mstosbt(fast_timer ? 95 : 995);
 	pr = mstosbt(10);
 	callout_reset_sbt(&is->is_callout, sbt, pr, iscsi_callout, is, 0);
 	TAILQ_INSERT_TAIL(&sc->sc_sessions, is, is_next);

sys/dev/iscsi/iscsi_ioctl.h

@@ -142,6 +142,8 @@ struct iscsi_daemon_handoff {
 	int				idh_max_send_data_segment_length;
 	int				idh_max_burst_length;
 	int				idh_first_burst_length;
+	int				idh_ping_timeout;
+	int				idh_login_timeout;
 };
 
 struct iscsi_daemon_fail {