On Tue, 2011-12-20 at 10:13 +0000, Bart Van Assche wrote:
> On Mon, Dec 19, 2011 at 10:32 PM, David Dillow <[email protected]> wrote:
> > I still think this is already solved in user space, but the new
> > reconnect model you've implemented doesn't match up with the expected
> > semantics. It'd be better to match the rest of the SCSI stack for this.
> 
> Sorry, but I'm afraid there is no "rest of the SCSI stack
> [semantics]". I've been following the semantics implemented in
> open-iscsi. If the semantics implemented for FC differ of those
> proposed in this patch set, then that means that the semantics
> implemented for FC differ of those for open-iscsi.

FC, SAS, SPI, (current) SRP, and FCoE currently use the same semantic to
check if the transport is still alive -- user space initiates activity,
usually via multipathd. You are changing SRP to match the iSCSI stack,
and because SRP does not have a NOP command, you have to fake one up
using Test Unit Ready to the first LUN to come through slave_alloc().
You kill the entire connection if that LUN has issues and causes a
timeout, though the rest of the LUNs may be fine and able to
communicate.

This is all handled properly by existing user space code; there's no
need for it to be in kernel, especially if you have to fake it while
going against the grain.
-- 
Dave Dillow
National Center for Computational Science
Oak Ridge National Laboratory
(865) 241-6602 office

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