Allow disabling auto LUN scans

Existing behavior of auto scanning LUNs is problematic for some
deployments, particularly in cases where we are:

- Accessing different LUNs from the same target on different machines
  and we don't want the other LUNs automatically exposed in other
  systems.

- LUNs are constantly being created and removed from the target by
  another machine and we don't want our systems polluted by no longer
  available logical units, since default udev rules don't remove them
  automatically from the system once they have been added automatically.

This is a little more problematic when working with multipaths as we end
up with a lot of leftover device maps.

This patch introduces a new configuration option at the session level
called "scan", with "auto" and "manual" as acceptable values, that
allows us to disable the autoscan in the following cases:

- On iscsid start
- On login
- On AEN/AER messages reporting LUNs data has changed.

For HW drivers all sessions will use the value defined in the
configuration file.

Default value for this new option is "auto" to maintain existing
behavior.

12 files changed, 41 insertions, 8 deletions

diff --git a/etc/iscsid.conf b/etc/iscsid.conf
index f7ecb6b..cb77a77 100644
--- a/etc/iscsid.conf
+++ b/etc/iscsid.conf
@@ -305,3 +305,11 @@ node.session.iscsi.FastAbort = Yes
 # a task management function like an ABORT TASK or LOGICAL UNIT RESET, that
 # it continue to respond to R2Ts. To enable this uncomment this line
 # node.session.iscsi.FastAbort = No
+
+# To prevent doing automatic scans that would add unwanted luns to the system
+# we can disable them and have sessions only do manually requested scans.
+# Automatic scans are performed on startup, on login, and on AEN/AER reception
+# on devices supporting it.  For HW drivers all sessions will use the value
+# defined in the configuration file.  This configuration option is independent
+# of scsi_mod scan parameter. (The default behavior is auto):
+node.session.scan = auto
diff --git a/usr/config.h b/usr/config.h
index 5b1bb1d..3bcb93f 100644
--- a/usr/config.h
+++ b/usr/config.h
@@ -190,6 +190,7 @@ typedef struct session_rec {
 	int					queue_depth;
 	int					initial_login_retry_max;
 	int					nr_sessions;
+	int					scan;
 	struct iscsi_auth_config		auth;
 	struct iscsi_session_timeout_config	timeo;
 	struct iscsi_error_timeout_config	err_timeo;
diff --git a/usr/idbm.c b/usr/idbm.c
index 3b8a5a2..ff8d67f 100644
--- a/usr/idbm.c
+++ b/usr/idbm.c
@@ -462,6 +462,9 @@ idbm_recinfo_node(node_rec_t *r, recinfo_t *ri)
 		      session.iscsi.MaxOutstandingR2T, IDBM_SHOW, num, 1);
 	__recinfo_int(SESSION_ERL, ri, r,
 		      session.iscsi.ERL, IDBM_SHOW, num, 1);
+	__recinfo_int_o2(SESSION_SCAN, ri, r,
+			 session.scan, IDBM_SHOW, "manual", "auto",
+			 num, 1);
 
 	for (i = 0; i < ISCSI_CONN_MAX; i++) {
 		char key[NAME_MAXVAL];
@@ -2490,7 +2493,7 @@ static void idbm_rm_disc_node_links(char *disc_dir)
 		log_debug(5, "disc removal removing link %s %s %s %s",
 			  target, address, port, iface_id);
 
-		memset(rec, 0, sizeof(*rec));	
+		memset(rec, 0, sizeof(*rec));
 		strlcpy(rec->name, target, TARGET_NAME_MAXLEN);
 		rec->tpgt = atoi(tpgt);
 		rec->conn[0].port = atoi(port);
@@ -2726,6 +2729,14 @@ idbm_slp_defaults(struct iscsi_slp_config *cfg)
 	       sizeof(struct iscsi_slp_config));
 }
 
+int
+idbm_session_autoscan(struct iscsi_session *session)
+{
+	if (session)
+		return session->nrec.session.scan;
+	return db->nrec.session.scan;
+}
+
 struct user_param *idbm_alloc_user_param(char *name, char *value)
 {
 	struct user_param *param;
@@ -2981,6 +2992,7 @@ void idbm_node_setup_defaults(node_rec_t *rec)
 	rec->session.info = NULL;
 	rec->session.sid = 0;
 	rec->session.multiple = 0;
+	rec->session.scan = DEF_INITIAL_SCAN;
 	idbm_setup_session_defaults(&rec->session.iscsi);
 
 	for (i=0; i<ISCSI_CONN_MAX; i++) {
diff --git a/usr/idbm.h b/usr/idbm.h
index b9020fe..411dd82 100644
--- a/usr/idbm.h
+++ b/usr/idbm.h
@@ -140,6 +140,7 @@ extern int idbm_add_discovery(discovery_rec_t *newrec);
 extern void idbm_sendtargets_defaults(struct iscsi_sendtargets_config *cfg);
 extern void idbm_isns_defaults(struct iscsi_isns_config *cfg);
 extern void idbm_slp_defaults(struct iscsi_slp_config *cfg);
+extern int idbm_session_autoscan(struct iscsi_session *session);
 extern int idbm_discovery_read(discovery_rec_t *rec, int type, char *addr,
 				int port);
 extern int idbm_rec_read(node_rec_t *out_rec, char *target_name,
diff --git a/usr/idbm_fields.h b/usr/idbm_fields.h
index 5790a03..4a92758 100644
--- a/usr/idbm_fields.h
+++ b/usr/idbm_fields.h
@@ -45,6 +45,7 @@
 #define SESSION_MAX_CONNS	"node.session.iscsi.MaxConnections"
 #define SESSION_MAX_R2T		"node.session.iscsi.MaxOutstandingR2T"
 #define SESSION_ERL		"node.session.iscsi.ERL"
+#define SESSION_SCAN		"node.session.scan"
 
 /* connections fields */
 #define CONN_ADDR		"node.conn[%d].address"
diff --git a/usr/initiator.c b/usr/initiator.c
index ed174b5..a86d1e6 100644
--- a/usr/initiator.c
+++ b/usr/initiator.c
@@ -997,7 +997,7 @@ static void session_scan_host(struct iscsi_session *session, int hostno,
 {
 	pid_t pid;
 
-	pid = iscsi_sysfs_scan_host(hostno, 1);
+	pid = iscsi_sysfs_scan_host(hostno, 1, idbm_session_autoscan(session));
 	if (pid == 0) {
 		mgmt_ipc_write_rsp(qtask, ISCSI_SUCCESS);
 
@@ -1201,7 +1201,8 @@ static void iscsi_recv_async_msg(iscsi_conn_t *conn, struct iscsi_hdr *hdr)
 			break;
 		}
 
-		if (sshdr.asc == 0x3f && sshdr.ascq == 0x0e)
+		if (sshdr.asc == 0x3f && sshdr.ascq == 0x0e
+		    && idbm_session_autoscan(session))
 			session_scan_host(session, session->hostno, NULL);
 		break;
 	case ISCSI_ASYNC_MSG_REQUEST_LOGOUT:
diff --git a/usr/iscsi_settings.h b/usr/iscsi_settings.h
index 3d923c8..296ff40 100644
--- a/usr/iscsi_settings.h
+++ b/usr/iscsi_settings.h
@@ -45,3 +45,6 @@
 
 /* login retries */
 #define DEF_INITIAL_LOGIN_RETRIES_MAX	4
+
+/* autoscan enabled */
+#define DEF_INITIAL_SCAN	1
diff --git a/usr/iscsi_sysfs.c b/usr/iscsi_sysfs.c
index 8ca668f..2f94b63 100644
--- a/usr/iscsi_sysfs.c
+++ b/usr/iscsi_sysfs.c
@@ -1883,12 +1883,15 @@ void iscsi_sysfs_rescan_device(void *data, int hostno, int target, int lun)
 			strlen(write_buf));
 }
 
-pid_t iscsi_sysfs_scan_host(int hostno, int async)
+pid_t iscsi_sysfs_scan_host(int hostno, int async, int full_scan)
 {
 	char id[NAME_SIZE];
-	char *write_buf = "- - -";
+	char write_buf[6] = "- - 0";
 	pid_t pid = 0;
 
+	if (full_scan)
+		write_buf[4] = '-';
+
 	if (async)
 		pid = fork();
 	if (pid == 0) {
diff --git a/usr/iscsi_sysfs.h b/usr/iscsi_sysfs.h
index 9a56105..3492ce6 100644
--- a/usr/iscsi_sysfs.h
+++ b/usr/iscsi_sysfs.h
@@ -87,7 +87,7 @@ extern void iscsi_sysfs_get_negotiated_session_conf(int sid,
 				struct iscsi_session_operational_config *conf);
 extern void iscsi_sysfs_get_negotiated_conn_conf(int sid,
 				struct iscsi_conn_operational_config *conf);
-extern pid_t iscsi_sysfs_scan_host(int hostno, int async);
+extern pid_t iscsi_sysfs_scan_host(int hostno, int async, int full);
 extern int iscsi_sysfs_get_session_state(char *state, int sid);
 extern int iscsi_sysfs_get_host_state(char *state, int host_no);
 extern int iscsi_sysfs_get_device_state(char *state, int host_no, int target,
diff --git a/usr/iscsiadm.c b/usr/iscsiadm.c
index 4b2bd34..90e2828 100644
--- a/usr/iscsiadm.c
+++ b/usr/iscsiadm.c
@@ -773,7 +773,7 @@ static int rescan_portal(void *data, struct session_info *info)
 	iscsi_sysfs_for_each_device(NULL, host_no, info->sid,
 				    iscsi_sysfs_rescan_device);
 	/* now scan for new devices */
-	iscsi_sysfs_scan_host(host_no, 0);
+	iscsi_sysfs_scan_host(host_no, 0, 1);
 	return 0;
 }
 
diff --git a/usr/iscsid.c b/usr/iscsid.c
index 81a14f2..813eb3d 100644
--- a/usr/iscsid.c
+++ b/usr/iscsid.c
@@ -216,7 +216,7 @@ static int sync_session(void *data, struct session_info *info)
 				  iscsi_err_to_str(err));
 			return 0;
 		}
-		iscsi_sysfs_scan_host(host_no, 0);
+		iscsi_sysfs_scan_host(host_no, 0, idbm_session_autoscan(NULL));
 		return 0;
 	}
 
diff --git a/usr/iscsistart.c b/usr/iscsistart.c
index 5cf0972..67ac475 100644
--- a/usr/iscsistart.c
+++ b/usr/iscsistart.c
@@ -140,6 +140,7 @@ static int apply_params(struct node_rec *rec)
 	rec->session.initial_login_retry_max = -1;
 	rec->conn[0].timeo.noop_out_interval = -1;
 	rec->conn[0].timeo.noop_out_timeout = -1;
+	rec->session.scan = -1;
 
 	list_for_each_entry(param, &user_params, list) {
 		/*
@@ -183,6 +184,8 @@ static int apply_params(struct node_rec *rec)
 		rec->conn[0].timeo.noop_out_interval = 0;
 	if (rec->conn[0].timeo.noop_out_timeout == -1)
 		rec->conn[0].timeo.noop_out_timeout = 0;
+	if (rec->session.scan == -1)
+		rec->session.scan = DEF_INITIAL_SCAN;
 
 	return 0;
 }