Re: [PATCH 03/28] libfc: IO errors on link down due to cable unplug

[Mike Christie <michaelc@cs.wisc.edu>]

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On 07/27/2010 04:32 PM, Vasu Dev wrote:
>> This isn't one of those races where you are blocking the rport, but the
>> IO keeps coming around so the retries are used really quickly right (the
>> driver looks like it has the fc class and internal state checks to
>> prevent this but I wanted to make sure).
>

I think I am hitting the above problem.

>
> This tiny time windows can be further reduced by use of wmb() on rport
> state change to block and lport getting out of ready since their states
> are checked w/o lock in queuecommand path.

I think you need something like this for the lport queue ready check. 
It looks like the initial failure from __fc_linkdown->fc_fcp_cleanup 
burned a timeout. Then because it missed the lport ready check, it will 
use an extra retry just sitting there timing out.

For the rport state check, I think you are supposed to call the fc 
chkready function under the host lock. The port state and flags are set 
under it. I did the attached patch for that.

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libfc: call fc_remote_port_chkready under the host lock.

The rport port state and flags are set under the host lock,
so this patch calls fc_remote_port_chkready with the host lock
held like is also done in the other fc drivers.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>

diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index eac4d09..a116846 100644
--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -1765,14 +1768,14 @@ int fc_queuecommand(struct scsi_cmnd *sc_cmd, void (*done)(struct scsi_cmnd *))
 	struct fcoe_dev_stats *stats;
 
 	lport = shost_priv(sc_cmd->device->host);
-	spin_unlock_irq(lport->host->host_lock);
 
 	rval = fc_remote_port_chkready(rport);
 	if (rval) {
 		sc_cmd->result = rval;
 		done(sc_cmd);
-		goto out;
+		return 0;
 	}
+	spin_unlock_irq(lport->host->host_lock);
 
 	if (!*(struct fc_remote_port **)rport->dd_data) {
 		/*