scsi: zfcp: fix reaction on bit error threshold notification

On excessive bit errors for the FCP channel ingress fibre path, the channel
notifies us.  Previously, we only emitted a kernel message and a trace
record.  Since performance can become suboptimal with I/O timeouts due to
bit errors, we now stop using an FCP device by default on channel
notification so multipath on top can timely failover to other paths.  A new
module parameter zfcp.ber_stop can be used to get zfcp old behavior.

User explanation of new kernel message:

 * Description:
 * The FCP channel reported that its bit error threshold has been exceeded.
 * These errors might result from a problem with the physical components
 * of the local fibre link into the FCP channel.
 * The problem might be damage or malfunction of the cable or
 * cable connection between the FCP channel and
 * the adjacent fabric switch port or the point-to-point peer.
 * Find details about the errors in the HBA trace for the FCP device.
 * The zfcp device driver closed down the FCP device
 * to limit the performance impact from possible I/O command timeouts.
 * User action:
 * Check for problems on the local fibre link, ensure that fibre optics are
 * clean and functional, and all cables are properly plugged.
 * After the repair action, you can manually recover the FCP device by
 * writing "0" into its "failed" sysfs attribute.
 * If recovery through sysfs is not possible, set the CHPID of the device
 * offline and back online on the service element.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: <stable@vger.kernel.org> #2.6.30+
Link: https://lore.kernel.org/r/20191001104949.42810-1-maier@linux.ibm.com
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/s390/scsi/zfcp_fsf.c

@@ -27,6 +27,11 @@
 
 struct kmem_cache *zfcp_fsf_qtcb_cache;
 
+static bool ber_stop = true;
+module_param(ber_stop, bool, 0600);
+MODULE_PARM_DESC(ber_stop,
+		 "Shuts down FCP devices for FCP channels that report a bit-error count in excess of its threshold (default on)");
+
 static void zfcp_fsf_request_timeout_handler(struct timer_list *t)
 {
 	struct zfcp_fsf_req *fsf_req = from_timer(fsf_req, t, timer);
@@ -236,10 +241,15 @@ static void zfcp_fsf_status_read_handler(struct zfcp_fsf_req *req)
 	case FSF_STATUS_READ_SENSE_DATA_AVAIL:
 		break;
 	case FSF_STATUS_READ_BIT_ERROR_THRESHOLD:
-		dev_warn(&adapter->ccw_device->dev,
-			 "The error threshold for checksum statistics "
-			 "has been exceeded\n");
 		zfcp_dbf_hba_bit_err("fssrh_3", req);
+		if (ber_stop) {
+			dev_warn(&adapter->ccw_device->dev,
+				 "All paths over this FCP device are disused because of excessive bit errors\n");
+			zfcp_erp_adapter_shutdown(adapter, 0, "fssrh_b");
+		} else {
+			dev_warn(&adapter->ccw_device->dev,
+				 "The error threshold for checksum statistics has been exceeded\n");
+		}
 		break;
 	case FSF_STATUS_READ_LINK_DOWN:
 		zfcp_fsf_status_read_link_down(req);