scsi: iscsi: Fix recovery and unblocking race

If the user sets the iscsi_eh_timer_workq/iscsi_eh workqueue's max_active
to greater than 1, the recovery_work could be running when
__iscsi_unblock_session() runs. The cancel_delayed_work() will then not
wait for the running work and we can race where we end up with the wrong
session state and scsi_device state set.

This replaces the cancel_delayed_work() with the sync version.

Link: https://lore.kernel.org/r/20220226230435.38733-2-michael.christie@oracle.comReviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_transport_iscsi.c

@@ -1917,11 +1917,8 @@ static void __iscsi_unblock_session(struct work_struct *work)
 	unsigned long flags;
 
 	ISCSI_DBG_TRANS_SESSION(session, "Unblocking session\n");
-	/*
-	 * The recovery and unblock work get run from the same workqueue,
-	 * so try to cancel it if it was going to run after this unblock.
-	 */
-	cancel_delayed_work(&session->recovery_work);
+
+	cancel_delayed_work_sync(&session->recovery_work);
 	spin_lock_irqsave(&session->lock, flags);
 	session->state = ISCSI_SESSION_LOGGED_IN;
 	spin_unlock_irqrestore(&session->lock, flags);