Re: [PATCH 0/2][RESEND] scsi_transport_fc: LUN masking

[Ewan Milne <emilne@redhat.com>]

On Tue, 2016-02-23 at 18:21 +0800, Hannes Reinecke wrote:
> On 02/22/2016 07:39 PM, Seymour, Shane M wrote:
> > Hi Hannes,
> > 
> > How do you know that a request for an async scan is complete (I'm assuming that you get
> > add or change udev events)? Assuming that someone has manually started a scan on something
> > (e.g. some newly presented devices after boot) and all scans are going
> to be async how
> > do you when it is complete rather than waiting in a work queue? An
> example may be a sysfs
> > file that contains unscanned, pending, scanning, scanned so you know
> when it's complete
> > at the appropriate level in sysfs (the hba and the rports) so you know
> when can continue
> > if you're polling the status (e.g. checking as part of system admin
> work with newly
> > presented rports so you can then do something with them).
> >
> Thing is, I don't.
> 
> We have had a similar discussion with the IBM zfcp folks, that it would
> be desirable to have a marker in sysfs telling us that the rport is
> stable (ie no scanning in progress).
> However, this cannot be at the rport level (as the rport itself might be
> going away), but rather at some higher level (eg fc_host).

I am not sure this really helps.  If another process initiates a scan
then sysfs might report that the scanning was still in progress.  If
scans are initiated often enough, you might never observe a stable state.

> 
> But this has nothing to do with the patchset, right?
> We're just disabling the (existing) scan callback, and retrigger it once
> the sysfs attribute has been cleared.
> 
> We don't change the behaviour during scanning with this patchset.
> 
> Cheers,
> 
> Hannes