scsi: qedf: Set the UNLOADING flag when removing a vport

Similar to what we do when we remove a PCI function, set the
QEDF_UNLOADING flag to prevent any requests from being queued while a
vport is being deleted.  This prevents any requests from getting stuck
in limbo when the vport is unloaded or deleted.

Fixes the crash:

PID: 106676  TASK: ffff9a436aa90000  CPU: 12  COMMAND: "multipathd"
 #0 [ffff9a43567d3550] machine_kexec+522 at ffffffffaca60b2a
 #1 [ffff9a43567d35b0] __crash_kexec+114 at ffffffffacb13512
 #2 [ffff9a43567d3680] crash_kexec+48 at ffffffffacb13600
 #3 [ffff9a43567d3698] oops_end+168 at ffffffffad117768
 #4 [ffff9a43567d36c0] no_context+645 at ffffffffad106f52
 #5 [ffff9a43567d3710] __bad_area_nosemaphore+116 at ffffffffad106fe9
 #6 [ffff9a43567d3760] bad_area+70 at ffffffffad107379
 #7 [ffff9a43567d3788] __do_page_fault+1247 at ffffffffad11a8cf
 #8 [ffff9a43567d37f0] do_page_fault+53 at ffffffffad11a915
 #9 [ffff9a43567d3820] page_fault+40 at ffffffffad116768
    [exception RIP: qedf_init_task+61]
    RIP: ffffffffc0e13c2d  RSP: ffff9a43567d38d0  RFLAGS: 00010046
    RAX: 0000000000000000  RBX: ffffbe920472c738  RCX: ffff9a434fa0e3e8
    RDX: ffff9a434f695280  RSI: ffffbe920472c738  RDI: ffff9a43aa359c80
    RBP: ffff9a43567d3950   R8: 0000000000000c15   R9: ffff9a3fb09b9880
    R10: ffff9a434fa0e3e8  R11: ffff9a43567d35ce  R12: 0000000000000000
    R13: ffff9a434f695280  R14: ffff9a43aa359c80  R15: ffff9a3fb9e005c0
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018

Signed-off-by: Chad Dupuis <chad.dupuis@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qedf/qedf_main.c

@@ -1677,6 +1677,15 @@ static int qedf_vport_destroy(struct fc_vport *vport)
 	struct Scsi_Host *shost = vport_to_shost(vport);
 	struct fc_lport *n_port = shost_priv(shost);
 	struct fc_lport *vn_port = vport->dd_data;
+	struct qedf_ctx *qedf = lport_priv(vn_port);
+
+	if (!qedf) {
+		QEDF_ERR(NULL, "qedf is NULL.\n");
+		goto out;
+	}
+
+	/* Set unloading bit on vport qedf_ctx to prevent more I/O */
+	set_bit(QEDF_UNLOADING, &qedf->flags);
 
 	mutex_lock(&n_port->lp_mutex);
 	list_del(&vn_port->list);
@@ -1703,6 +1712,7 @@ static int qedf_vport_destroy(struct fc_vport *vport)
 	if (vn_port->host)
 		scsi_host_put(vn_port->host);
 
+out:
 	return 0;
 }