scsi: ibmvfc: Handle move login failure

scsi: ibmvfc: Handle move login failure

When service is being performed on an SVC with NPIV enabled, the WWPN of
the canister / node being serviced fails over to the another canister /
node. This looks to the ibmvfc driver as a WWPN moving from one SCSI ID to
another. The driver will first attempt to do an implicit logout of the old
SCSI ID. If this works, we simply delete the rport at the old location and
add an rport at the new location and the FC transport class handles
everything. However, if there is I/O outstanding, this implicit logout will
fail, in which case we will send a "move login" request to the VIOS. This
will cancel any outstanding I/O to that port, logout the port, and PLOGI
the new port. Recently we've encountered a scenario where the move login
fails. This was resulting in an attempted plogi to the new scsi id, without
the old scsi id getting logged out, which is a VIOS protocol violation. To
solve this, we want to keep tracking the old scsi id as the current scsi
id. That way, once terminate_rport_io cancels the outstanding i/o, it will
send us back through to do an implicit logout of the old scsi id, rather
than the new scsi id, and then we can plogi the new scsi id.

Link: https://lore.kernel.org/r/1620756740-7045-2-git-send-email-brking@linux.vnet.ibm.com
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>