[PATCH v2] zfcp: fix reaction on bit error theshold notification with adapter close

[Steffen Maier <maier@linux.ibm.com>]

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.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: <stable@vger.kernel.org> #2.6.30+
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
---

Martin, James,

an important zfcp fix for v5.4-rc.
It applies to Martin's 5.4/scsi-fixes or to James' fixes branch.

Changes since v1:
* Martin's review comments: describe code change and new module parameter


 drivers/s390/scsi/zfcp_fsf.c | 16 +++++++++++++---
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index e31c6b47af97..1e279220f073 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -29,6 +29,11 @@
 
 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);
@@ -238,10 +243,15 @@ 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);
-- 
2.17.1