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[SCSI] scsi_transport_fc: Remove capping from dev_loss_tmo 

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>
Acked-by: James Smart  <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
This commit is contained in:
Hannes Reinecke 2009-12-15 09:26:06 +01:00 committed by James Bottomley
parent e47c11c7a4
commit f2818663c8
1 changed files with 21 additions and 5 deletions
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26
drivers/scsi/scsi_transport_fc.c
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@ -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
@ -842,9 +843,17 @@ 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;
}
@ -925,9 +934,16 @@ 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;