Re: [dm-devel] [Lsf] Notes from the four separate IO track sessions at LSF/MM

[Laurence Oberman <loberman@redhat.com>]

----- Original Message -----
From: "Bart Van Assche" <bart.vanassche@sandisk.com>
To: "Laurence Oberman" <loberman@redhat.com>
Cc: "James Bottomley" <James.Bottomley@HansenPartnership.com>, "linux-scsi" <linux-scsi@vger.kernel.org>, "Mike Snitzer" <snitzer@redhat.com>, linux-block@vger.kernel.org, "device-mapper development" <dm-devel@redhat.com>, lsf@lists.linux-foundation.org
Sent: Monday, May 2, 2016 6:28:16 PM
Subject: Re: [dm-devel] [Lsf] Notes from the four separate IO track sessions at LSF/MM

On 05/02/2016 12:28 PM, Laurence Oberman wrote:
> Even in the case of the ib_srp, don't we also have to still run the
> eh_timeout for each of the devices that has inflight requiring error
> handling serially. This means we will still have to wait to get a
> path failover until all are through the timeout.

Hello Laurence,

It depends. If a transport layer error (e.g. a cable pull) has been 
observed by the ib_srp driver then fast_io_fail_tmo seconds later the 
ib_srp driver will terminate all outstanding SCSI commands without 
waiting for the error handler to finish. If no transport layer error has 
been observed then at most (SCSI timeout) + (number of pending commands 
+ 1) * 5 seconds later srp_reset_device() will have finished terminating 
all pending SCSI commands.

Bart.
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Hello Bart

OK, Yes, that lines up with my testing here with Qlogic and Emulex.
I am about to test srp but I need to add some jammer code first.
The link down and other interruptions will always be fast. 
Its always going to be the black-hole events that are troublesome.

Thanks
Laurence