scsi: zfcp: Defer fc_rport blocking until after ADISC response

Storage devices are free to send RSCNs, e.g. for internal state changes. If
this happens on all connected paths, zfcp risks temporarily losing all
paths at the same time. This has strong requirements on multipath
configuration such as "no_path_retry queue".

Avoid such situations by deferring fc_rport blocking until after the ADISC
response, when any actual state change of the remote port became clear.
The already existing port recovery triggers explicitly block the fc_rport.
The triggers are: on ADISC reject or timeout (typical cable pull case), and
on ADISC indicating that the remote port has changed its WWPN or
the port is meanwhile no longer open.

As a side effect, this also removes a confusing direct function call to
another work item function zfcp_scsi_rport_work() instead of scheduling
that other work item. It was probably done that way to have the rport block
side effect immediate and synchronous to the caller.

Fixes: a2fa0ae ("[SCSI] zfcp: Block FC transport rports early on errors")
Cc: stable@vger.kernel.org #v2.6.30+
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Fedor Loshakov <loshakov@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Link: https://lore.kernel.org/r/20230724145156.3920244-1-maier@linux.ibm.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: steffen-maier

drivers/s390/scsi/zfcp_fc.c

@@ -534,8 +534,7 @@ static void zfcp_fc_adisc_handler(void *data)
 
 	/* re-init to undo drop from zfcp_fc_adisc() */
 	port->d_id = ntoh24(adisc_resp->adisc_port_id);
-	/* port is good, unblock rport without going through erp */
-	zfcp_scsi_schedule_rport_register(port);
+	/* port is still good, nothing to do */
  out:
 	atomic_andnot(ZFCP_STATUS_PORT_LINK_TEST, &port->status);
 	put_device(&port->dev);
@@ -595,9 +594,6 @@ void zfcp_fc_link_test_work(struct work_struct *work)
 	int retval;
 
 	set_worker_desc("zadisc%16llx", port->wwpn); /* < WORKER_DESC_LEN=24 */
-	get_device(&port->dev);
-	port->rport_task = RPORT_DEL;
-	zfcp_scsi_rport_work(&port->rport_work);
 
 	/* only issue one test command at one time per port */
 	if (atomic_read(&port->status) & ZFCP_STATUS_PORT_LINK_TEST)