[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, 7 insertions, 0 deletions

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index df0c3c71ea43..f334859024c0 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -316,6 +316,12 @@ static void scsi_host_dev_release(struct device *dev)
         kfree(shost);
 }
 
+static unsigned int shost_eh_deadline;
+
+module_param_named(eh_deadline, shost_eh_deadline, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(eh_deadline,
+                 "SCSI EH timeout in seconds (should be between 1 and 2^32-1)");
+
 static struct device_type scsi_host_type = {
         .name =         "scsi_host",
         .release =      scsi_host_dev_release,
@@ -388,6 +394,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
         shost->unchecked_isa_dma = sht->unchecked_isa_dma;
         shost->use_clustering = sht->use_clustering;
         shost->ordered_tag = sht->ordered_tag;
+        shost->eh_deadline = shost_eh_deadline * HZ;
 
         if (sht->supported_mode == MODE_UNKNOWN)
                 /* means we didn't set it ... default to INITIATOR */