s390/dasd: channel path aware error recovery

With this feature, the DASD device driver more robustly handles DASDs
that are attached via multiple channel paths and are subject to
constant Interface-Control-Checks (IFCCs) and Channel-Control-Checks
(CCCs) or loss of High-Performance-FICON (HPF) functionality on one or
more of these paths.

If a channel path does not work correctly, it is removed from normal
operation as long as other channel paths are available. All extended
error recovery states can be queried and reset via user space
interfaces.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 151 insertions, 6 deletions

diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index 4101ab000c16..84ca314c87e3 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -977,10 +977,12 @@ dasd_access_show(struct device *dev, struct device_attribute *attr,
 	if (IS_ERR(device))
 		return PTR_ERR(device);
 
-	if (device->discipline->host_access_count)
-		count = device->discipline->host_access_count(device);
-	else
+	if (!device->discipline)
+		count = -ENODEV;
+	else if (!device->discipline->host_access_count)
 		count = -EOPNOTSUPP;
+	else
+		count = device->discipline->host_access_count(device);
 
 	dasd_put_device(device);
 	if (count < 0)
@@ -1341,6 +1343,50 @@ dasd_timeout_store(struct device *dev, struct device_attribute *attr,
 static DEVICE_ATTR(timeout, 0644,
 		   dasd_timeout_show, dasd_timeout_store);
 
+
+static ssize_t
+dasd_path_reset_store(struct device *dev, struct device_attribute *attr,
+		      const char *buf, size_t count)
+{
+	struct dasd_device *device;
+	unsigned int val;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+
+	if ((kstrtouint(buf, 16, &val) != 0) || val > 0xff)
+		val = 0;
+
+	if (device->discipline && device->discipline->reset_path)
+		device->discipline->reset_path(device, (__u8) val);
+
+	dasd_put_device(device);
+	return count;
+}
+
+static DEVICE_ATTR(path_reset, 0200, NULL, dasd_path_reset_store);
+
+static ssize_t dasd_hpf_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct dasd_device *device;
+	int hpf;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+	if (!device->discipline || !device->discipline->hpf_enabled) {
+		dasd_put_device(device);
+		return snprintf(buf, PAGE_SIZE, "%d\n", dasd_nofcx);
+	}
+	hpf = device->discipline->hpf_enabled(device);
+	dasd_put_device(device);
+	return snprintf(buf, PAGE_SIZE, "%d\n", hpf);
+}
+
+static DEVICE_ATTR(hpf, 0444, dasd_hpf_show, NULL);
+
 static ssize_t dasd_reservation_policy_show(struct device *dev,
 					    struct device_attribute *attr,
 					    char *buf)
@@ -1432,7 +1478,7 @@ static ssize_t dasd_pm_show(struct device *dev,
 			      struct device_attribute *attr, char *buf)
 {
 	struct dasd_device *device;
-	u8 opm, nppm, cablepm, cuirpm, hpfpm;
+	u8 opm, nppm, cablepm, cuirpm, hpfpm, ifccpm;
 
 	device = dasd_device_from_cdev(to_ccwdev(dev));
 	if (IS_ERR(device))
@@ -1443,14 +1489,109 @@ static ssize_t dasd_pm_show(struct device *dev,
 	cablepm = dasd_path_get_cablepm(device);
 	cuirpm = dasd_path_get_cuirpm(device);
 	hpfpm = dasd_path_get_hpfpm(device);
+	ifccpm = dasd_path_get_ifccpm(device);
 	dasd_put_device(device);
 
-	return sprintf(buf, "%02x %02x %02x %02x %02x\n", opm, nppm,
-		       cablepm, cuirpm, hpfpm);
+	return sprintf(buf, "%02x %02x %02x %02x %02x %02x\n", opm, nppm,
+		       cablepm, cuirpm, hpfpm, ifccpm);
 }
 
 static DEVICE_ATTR(path_masks, 0444, dasd_pm_show, NULL);
 
+/*
+ * threshold value for IFCC/CCC errors
+ */
+static ssize_t
+dasd_path_threshold_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct dasd_device *device;
+	int len;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+	len = snprintf(buf, PAGE_SIZE, "%lu\n", device->path_thrhld);
+	dasd_put_device(device);
+	return len;
+}
+
+static ssize_t
+dasd_path_threshold_store(struct device *dev, struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct dasd_device *device;
+	unsigned long flags;
+	unsigned long val;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+
+	if ((kstrtoul(buf, 10, &val) != 0) ||
+	    (val > DASD_THRHLD_MAX) || val == 0) {
+		dasd_put_device(device);
+		return -EINVAL;
+	}
+	spin_lock_irqsave(get_ccwdev_lock(to_ccwdev(dev)), flags);
+	if (val)
+		device->path_thrhld = val;
+	spin_unlock_irqrestore(get_ccwdev_lock(to_ccwdev(dev)), flags);
+	dasd_put_device(device);
+	return count;
+}
+
+static DEVICE_ATTR(path_threshold, 0644, dasd_path_threshold_show,
+		   dasd_path_threshold_store);
+/*
+ * interval for IFCC/CCC checks
+ * meaning time with no IFCC/CCC error before the error counter
+ * gets reset
+ */
+static ssize_t
+dasd_path_interval_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct dasd_device *device;
+	int len;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+	len = snprintf(buf, PAGE_SIZE, "%lu\n", device->path_interval);
+	dasd_put_device(device);
+	return len;
+}
+
+static ssize_t
+dasd_path_interval_store(struct device *dev, struct device_attribute *attr,
+	       const char *buf, size_t count)
+{
+	struct dasd_device *device;
+	unsigned long flags;
+	unsigned long val;
+
+	device = dasd_device_from_cdev(to_ccwdev(dev));
+	if (IS_ERR(device))
+		return -ENODEV;
+
+	if ((kstrtoul(buf, 10, &val) != 0) ||
+	    (val > DASD_INTERVAL_MAX) || val == 0) {
+		dasd_put_device(device);
+		return -EINVAL;
+	}
+	spin_lock_irqsave(get_ccwdev_lock(to_ccwdev(dev)), flags);
+	if (val)
+		device->path_interval = val;
+	spin_unlock_irqrestore(get_ccwdev_lock(to_ccwdev(dev)), flags);
+	dasd_put_device(device);
+	return count;
+}
+
+static DEVICE_ATTR(path_interval, 0644, dasd_path_interval_show,
+		   dasd_path_interval_store);
+
+
 static struct attribute * dasd_attrs[] = {
 	&dev_attr_readonly.attr,
 	&dev_attr_discipline.attr,
@@ -1471,6 +1612,10 @@ static struct attribute * dasd_attrs[] = {
 	&dev_attr_safe_offline.attr,
 	&dev_attr_host_access_count.attr,
 	&dev_attr_path_masks.attr,
+	&dev_attr_path_threshold.attr,
+	&dev_attr_path_interval.attr,
+	&dev_attr_path_reset.attr,
+	&dev_attr_hpf.attr,
 	NULL,
 };