loop/usb/vhost-scsi/xen-scsiback: Fix use of __transport_register_session

This patch changes loopback, usb-gadget, vhost-scsi and xen-scsiback
fabric code to invoke transport_register_session() instead of the
unprotected flavour, to ensure se_tpg->session_lock is taken when
adding new session list nodes to se_tpg->tpg_sess_list.

Note that since these four fabric drivers already hold their own
internal TPG mutexes when accessing se_tpg->tpg_sess_list, and
consist of a single se_session created through configfs attribute
access, no list corruption can currently occur.

So for correctness sake, go ahead and use the se_tpg->session_lock
protected version for these four fabric drivers.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/loopback/tcm_loop.c

@@ -953,11 +953,8 @@ static int tcm_loop_make_nexus(
 		transport_free_session(tl_nexus->se_sess);
 		goto out;
 	}
-	/*
-	 * Now, register the SAS I_T Nexus as active with the call to
-	 * transport_register_session()
-	 */
-	__transport_register_session(se_tpg, tl_nexus->se_sess->se_node_acl,
+	/* Now, register the SAS I_T Nexus as active. */
+	transport_register_session(se_tpg, tl_nexus->se_sess->se_node_acl,
 			tl_nexus->se_sess, tl_nexus);
 	tl_tpg->tl_nexus = tl_nexus;
 	pr_debug("TCM_Loop_ConfigFS: Established I_T Nexus to emulated"

drivers/usb/gadget/legacy/tcm_usb_gadget.c

@@ -1740,10 +1740,9 @@ static int tcm_usbg_make_nexus(struct usbg_tpg *tpg, char *name)
 		goto err_session;
 	}
 	/*
-	 * Now register the TCM vHost virtual I_T Nexus as active with the
-	 * call to __transport_register_session()
+	 * Now register the TCM vHost virtual I_T Nexus as active.
 	 */
-	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
+	transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
 			tv_nexus->tvn_se_sess, tv_nexus);
 	tpg->tpg_nexus = tv_nexus;
 	mutex_unlock(&tpg->tpg_mutex);

drivers/vhost/scsi.c

@@ -1956,10 +1956,9 @@ static int vhost_scsi_make_nexus(struct vhost_scsi_tpg *tpg,
 		goto out;
 	}
 	/*
-	 * Now register the TCM vhost virtual I_T Nexus as active with the
-	 * call to __transport_register_session()
+	 * Now register the TCM vhost virtual I_T Nexus as active.
 	 */
-	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
+	transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
 			tv_nexus->tvn_se_sess, tv_nexus);
 	tpg->tpg_nexus = tv_nexus;
 

drivers/xen/xen-scsiback.c

@@ -1661,11 +1661,8 @@ static int scsiback_make_nexus(struct scsiback_tpg *tpg,
 			 name);
 		goto out;
 	}
-	/*
-	 * Now register the TCM pvscsi virtual I_T Nexus as active with the
-	 * call to __transport_register_session()
-	 */
-	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
+	/* Now register the TCM pvscsi virtual I_T Nexus as active. */
+	transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
 			tv_nexus->tvn_se_sess, tv_nexus);
 	tpg->tpg_nexus = tv_nexus;