scsi: core: Add a precondition check in scsi_eh_scmd_add()

Calling scsi_eh_scmd_add() may cause the error handler never to be woken up
because this may result in shost->host_failed to become larger than
scsi_host_busy(shost). Hence complain if scsi_eh_scmd_add() is called after
SCMD_STATE_INFLIGHT has been cleared.

Cc: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20231115193343.2262013-1-bvanassche@acm.orgSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_error.c

@@ -301,6 +301,7 @@ void scsi_eh_scmd_add(struct scsi_cmnd *scmd)
 	int ret;
 
 	WARN_ON_ONCE(!shost->ehandler);
+	WARN_ON_ONCE(!test_bit(SCMD_STATE_INFLIGHT, &scmd->state));
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsi_host_set_state(shost, SHOST_RECOVERY)) {