[SCSI] Add 'eh_deadline' to limit SCSI EH runtime

This patchs adds an 'eh_deadline' sysfs attribute to the scsi
host which limits the overall runtime of the SCSI EH.
The 'eh_deadline' value is stored in the now obsolete field
'resetting'.
When a command is failed the start time of the EH is stored
in 'last_reset'. If the overall runtime of the SCSI EH is longer
than last_reset + eh_deadline, the EH is short-circuited and
falls through to issue a host reset only.

[jejb: add comments in Scsi_Host about new fields]
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index a73471074a02..8ff62c26a41c 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -281,6 +281,42 @@ exit_store_host_reset:
 
 static DEVICE_ATTR(host_reset, S_IWUSR, NULL, store_host_reset);
 
+static ssize_t
+show_shost_eh_deadline(struct device *dev,
+		      struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+
+	return sprintf(buf, "%d\n", shost->eh_deadline / HZ);
+}
+
+static ssize_t
+store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	int ret = -EINVAL;
+	int deadline;
+	unsigned long flags;
+
+	if (shost->transportt && shost->transportt->eh_strategy_handler)
+		return ret;
+
+	if (sscanf(buf, "%d\n", &deadline) == 1) {
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_in_recovery(shost))
+			ret = -EBUSY;
+		else {
+			shost->eh_deadline = deadline * HZ;
+			ret = count;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
+	}
+	return ret;
+}
+
+static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
+
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(host_busy, "%hu\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");
@@ -308,6 +344,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	&dev_attr_prot_capabilities.attr,
 	&dev_attr_prot_guard_type.attr,
 	&dev_attr_host_reset.attr,
+	&dev_attr_eh_deadline.attr,
 	NULL
 };