[PATCH v2] scsi: qla2xxx: Keep initiator ports after RSCN

[Roman Bolshakov <r.bolshakov@yadro.com>]

The driver performs SCR (state change registration) in all modes
including pure target mode.

For each RSCN, scan_needed flag is set in qla2x00_handle_rscn() for the
port mentioned in the RSCN and fabric rescan is scheduled. During the
rescan, GNN_FT handler, qla24xx_async_gnnft_done() deletes session of
the port that caused the RSCN.

In target mode, the session deletion has an impact on ATIO handler,
qlt_24xx_atio_pkt(). Target responds with SAM STATUS BUSY to I/O
incoming from the deleted session. qlt_handle_cmd_for_atio() and
qlt_handle_task_mgmt() return -EFAULT if they are not able to find
session of the command/TMF, and that results in invocation of
qlt_send_busy():

  qlt_24xx_atio_pkt_all_vps: qla_target(0): type 6 ox_id 0014
  qla_target(0): Unable to send command to target, sending BUSY status

Such response causes command timeout on the initiator. Error handler
thread on the initiator will be spawned to abort the commands:

  scsi 23:0:0:0: tag#0 abort scheduled
  scsi 23:0:0:0: tag#0 aborting command
  qla2xxx [0000:af:00.0]-188c:23: Entered qla24xx_abort_command.
  qla2xxx [0000:af:00.0]-801c:23: Abort command issued nexus#:0:0 -- 0 2003.

Command abort is rejected by target and fails (2003), error handler then
tries to perform DEVICE RESET and TARGET RESET but they're also doomed
to fail because TMFs are ignored for the deleted sessions.

Then initiator makes BUS RESET that resets the link via
qla2x00_full_login_lip(). BUS RESET succeeds and brings initiator port
up, SAN switch detects that and sends RSCN to the target port and it
fails again the same way as described above. It never goes out of the
loop.

The change breaks the RSCN loop by keeping initiator sessions mentioned
in RSCN payload in all modes, including dual and pure target mode.

Fixes: 2037ce49d30a ("scsi: qla2xxx: Fix stale session")
Cc: Quinn Tran <qutran@marvell.com>
Cc: Arun Easi <aeasi@marvell.com>
Cc: Nilesh Javali <njavali@marvell.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Daniel Wagner <dwagner@suse.de>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Cc: Martin Wilck <mwilck@suse.com>
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 drivers/scsi/qla2xxx/qla_gs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Changes since v1:
  - Corrected an error when N_Port_ID change wouldn't clean up stale
    session (Martin W.).

    N_Port_ID may change in the switched fabric topology if initiator
    cable is replugged to another physical port on the SAN switch (some
    fabrics assign physical port number to domain area). Physical
    reconnection implies that initiator is going to relogin anyway and
    previous session is no longer needed.

diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c
index 42c3ad27f1cb..df670fba2ab8 100644
--- a/drivers/scsi/qla2xxx/qla_gs.c
+++ b/drivers/scsi/qla2xxx/qla_gs.c
@@ -3496,7 +3496,9 @@ void qla24xx_async_gnnft_done(scsi_qla_host_t *vha, srb_t *sp)
 				qla2x00_clear_loop_id(fcport);
 				fcport->flags |= FCF_FABRIC_DEVICE;
 			} else if (fcport->d_id.b24 != rp->id.b24 ||
-				fcport->scan_needed) {
+				   (fcport->scan_needed &&
+				    fcport->port_type != FCT_INITIATOR &&
+				    fcport->port_type != FCT_NVME_INITIATOR)) {
 				qlt_schedule_sess_for_deletion(fcport);
 			}
 			fcport->d_id.b24 = rp->id.b24;
-- 
2.26.1