scsi: lpfc: Fix duplicate unreg_rpi error in port offline flow

If the driver receives a login that is later then LOGO'd by the remote port
(aka ndlp), the driver, upon the completion of the LOGO ACC transmission,
will logout the node and unregister the rpi that is being used for the
node.  As part of the unreg, the node's rpi value is replaced by the
LPFC_RPI_ALLOC_ERROR value.  If the port is subsequently offlined, the
offline walks the nodes and ensures they are logged out, which possibly
entails unreg'ing their rpi values.  This path does not validate the node's
rpi value, thus doesn't detect that it has been unreg'd already.  The
replaced rpi value is then used when accessing the rpi bitmask array which
tracks active rpi values.  As the LPFC_RPI_ALLOC_ERROR value is not a valid
index for the bitmask, it may fault the system.

Revise the rpi release code to detect when the rpi value is the replaced
RPI_ALLOC_ERROR value and ignore further release steps.

Link: https://lore.kernel.org/r/20191105005708.7399-2-jsmart2021@gmail.comSigned-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_sli.c

@@ -18247,6 +18247,13 @@ lpfc_sli4_alloc_rpi(struct lpfc_hba *phba)
 static void
 __lpfc_sli4_free_rpi(struct lpfc_hba *phba, int rpi)
 {
+	/*
+	 * if the rpi value indicates a prior unreg has already
+	 * been done, skip the unreg.
+	 */
+	if (rpi == LPFC_RPI_ALLOC_ERROR)
+		return;
+
 	if (test_and_clear_bit(rpi, phba->sli4_hba.rpi_bmask)) {
 		phba->sli4_hba.rpi_count--;
 		phba->sli4_hba.max_cfg_param.rpi_used--;