Re: [PATCH] scsi: sd: add runtime pm to open / release

Alan Stern
2020-08-11T13:48:54Z

On Tue, Aug 11, 2020 at 09:55:54AM +0200, Martin Kepplinger wrote:
> On 10.08.20 16:13, Alan Stern wrote:
> > This may not matter... but it's worth pointing out that
> > expecting_media_change doesn't get cleared if ++scmd->retries >
> > scmd->allowed.
>
> absolutely worth pointing out and I'm not yet sure about that one.
>
> >
> > It also doesn't get cleared in cases where the device _doesn't_
> > report a Unit Attention.
>
> true. but don't we set the flag for a future UA we don't yet know of? If
> we would want to clear it outside of a UA, I think we'd need to keep
> track of a suspend/resume cycle and if we see that we *had* successfully
> "done requests" after resuming, we could clear it...

The point is that expecting_media_change should apply only to the _next_
command. It should be cleared after _every_ command. You do not want
to leave it hanging around -- if you do then you will miss real media
changes.

There's a potential issue when a bunch of commands get sent and
completed all at once, but hopefully it won't matter here.

Alan Stern