[PATCH 3.16 015/136] scsi: zfcp: fix reaction on bit error threshold notification

Ben Hutchings
2019-12-17T01:01:03Z

From: Steffen Maier <maier@linux.ibm.com>

commit 2190168aaea42c31bff7b9a967e7b045f07df095 upstream.

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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/s390/scsi/zfcp_fsf.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -20,6 +20,11 @@

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(unsigned long data)
{
struct zfcp_adapter *adapter = (struct zfcp_adapter *) data;
@@ -231,10 +236,15 @@ static void zfcp_fsf_status_read_handler
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);