[PATCH] Remove capping from dev_loss_tmo

Hannes Reinecke
2009-12-15T08:26:11Z

Currently dev_loss_tmo is capped by SCSI_DEVICE_BLOCK_MAX_TIMEOUT.
This causes problem with multipathing when the 'no_path_retry' setting
exceeds the dev_loss_tmo setting, as then the system might run into
a deadlock when all paths have been removed temporarily for longer
than dev_loss_tmo.
The principal reasons for the capping has been that we should
not allow a remote port to remain in status 'blocked' indefinitely,
so the capping is there to ensure that the port status is being reset
eventually.
However, the fast_io_fail_tmo will also move the remote port out of
the 'blocked' state, so for any HBA driver implementing both the
capping should really be on the fast_io_fail_tmo, and not on the
dev_loss_tmo.
This patch implements just that, ie the fast_io_fail_tmo is capped
to SCSI_DEVICE_BLOCK_TIMEOUT and the capping is removed from
dev_loss_tmo when fast_io_fail_tmo is set.
This allows us to synchronize the dev_loss_tmo setting to the
'no_path_retry' setting from multipathing thus avoiding the deadlock.

Signed-off-by: Hannes Reinecke <hare@suse.de>

diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c
index 573ce21..6f39bf4 100644
--- a/drivers/scsi/scsi_transport_fc.c
+++ b/drivers/scsi/scsi_transport_fc.c
@@ -475,7 +475,8 @@ MODULE_PARM_DESC(dev_loss_tmo,
"Maximum number of seconds that the FC transport should"
" insulate the loss of a remote port. Once this value is"
" exceeded, the scsi target is removed. Value should be"
- " between 1 and SCSI_DEVICE_BLOCK_MAX_TIMEOUT.");
+ " between 1 and SCSI_DEVICE_BLOCK_MAX_TIMEOUT if"
+ " fast_io_fail_tmo is not set.");

/*
* Netlink Infrastructure
@@ -831,9 +832,17 @@ store_fc_rport_dev_loss_tmo(struct device *dev, struct device_attribute *attr,
(rport->port_state == FC_PORTSTATE_NOTPRESENT))
return -EBUSY;
val = simple_strtoul(buf, &cp, 0);
- if ((*cp && (*cp != '\n')) ||
- (val < 0) || (val > SCSI_DEVICE_BLOCK_MAX_TIMEOUT))
+ if ((*cp && (*cp != '\n')) || (val < 0))
return -EINVAL;
+
+ /*
+ * If fast_io_fail is off we have to cap
+ * dev_loss_tmo at SCSI_DEVICE_BLOCK_MAX_TIMEOUT
+ */
+ if (rport->fast_io_fail_tmo == -1 &&
+ val > SCSI_DEVICE_BLOCK_MAX_TIMEOUT)
+ return -EINVAL;
+
i->f->set_rport_dev_loss_tmo(rport, val);
return count;
}
@@ -914,9 +923,16 @@ store_fc_rport_fast_io_fail_tmo(struct device *dev,
rport->fast_io_fail_tmo = -1;
else {
val = simple_strtoul(buf, &cp, 0);
- if ((*cp && (*cp != '\n')) ||
- (val < 0) || (val >= rport->dev_loss_tmo))
+ if ((*cp && (*cp != '\n')) || (val < 0))
return -EINVAL;
+ /*
+ * Cap fast_io_fail by dev_loss_tmo or
+ * SCSI_DEVICE_BLOCK_MAX_TIMEOUT.
+ */
+ if ((val >= rport->dev_loss_tmo) ||
+ (val > SCSI_DEVICE_BLOCK_MAX_TIMEOUT))
+ return -EINVAL;
+
rport->fast_io_fail_tmo = val;
}
return count;