scsi: qla2xxx: set UNLOADING before waiting for session deletion

The purpose of the UNLOADING flag is to avoid port login procedures to
continue when a controller is in the process of shutting down.  It makes
sense to set this flag before starting session teardown.

Furthermore, use atomic test_and_set_bit() to avoid the shutdown being run
multiple times in parallel. In qla2x00_disable_board_on_pci_error(), the
test for UNLOADING is postponed until after the check for an already
disabled PCI board.

Link: https://lore.kernel.org/r/20200421204621.19228-2-mwilck@suse.com
Fixes: 45235022 ("scsi: qla2xxx: Fix driver unload by shutting down chip")
Reviewed-by: Arun Easi <aeasi@marvell.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_os.c

@@ -3732,6 +3732,13 @@ qla2x00_remove_one(struct pci_dev *pdev)
 	}
 	qla2x00_wait_for_hba_ready(base_vha);
 
+	/*
+	 * if UNLOADING flag is already set, then continue unload,
+	 * where it was set first.
+	 */
+	if (test_and_set_bit(UNLOADING, &base_vha->dpc_flags))
+		return;
+
 	if (IS_QLA25XX(ha) || IS_QLA2031(ha) || IS_QLA27XX(ha) ||
 	    IS_QLA28XX(ha)) {
 		if (ha->flags.fw_started)
@@ -3750,15 +3757,6 @@ qla2x00_remove_one(struct pci_dev *pdev)
 
 	qla2x00_wait_for_sess_deletion(base_vha);
 
-	/*
-	 * if UNLOAD flag is already set, then continue unload,
-	 * where it was set first.
-	 */
-	if (test_bit(UNLOADING, &base_vha->dpc_flags))
-		return;
-
-	set_bit(UNLOADING, &base_vha->dpc_flags);
-
 	qla_nvme_delete(base_vha);
 
 	dma_free_coherent(&ha->pdev->dev,
@@ -6628,13 +6626,6 @@ qla2x00_disable_board_on_pci_error(struct work_struct *work)
 	struct pci_dev *pdev = ha->pdev;
 	scsi_qla_host_t *base_vha = pci_get_drvdata(ha->pdev);
 
-	/*
-	 * if UNLOAD flag is already set, then continue unload,
-	 * where it was set first.
-	 */
-	if (test_bit(UNLOADING, &base_vha->dpc_flags))
-		return;
-
 	ql_log(ql_log_warn, base_vha, 0x015b,
 	    "Disabling adapter.\n");
 
@@ -6645,9 +6636,14 @@ qla2x00_disable_board_on_pci_error(struct work_struct *work)
 		return;
 	}
 
-	qla2x00_wait_for_sess_deletion(base_vha);
+	/*
+	 * if UNLOADING flag is already set, then continue unload,
+	 * where it was set first.
+	 */
+	if (test_and_set_bit(UNLOADING, &base_vha->dpc_flags))
+		return;
 
-	set_bit(UNLOADING, &base_vha->dpc_flags);
+	qla2x00_wait_for_sess_deletion(base_vha);
 
 	qla2x00_delete_all_vps(ha, base_vha);