Re: [PATCH 1/3] scsi_dh: Add modalias support for SCSI targets

Chandra Seetharaman
2009-04-07T23:50:05Z

Thanks for your comment, Hannes.

On Wed, 2009-04-08 at 01:22 +0200, Hannes Reinecke wrote:
> Hi Chandra,
>
> On Fri, Apr 03, 2009 at 03:43:10PM -0700, Chandra Seetharaman wrote:
> > Hi James,
> >
> > Do you still have any concerns (after Peter's response) ?
> >
> > If not, Can you accept the patches, please.
> >
> The problem here is that module autoloading doesn't work for
> device_handler. We have to have the callbacks in place _before_
> driver probing starts as we might need to intercept the I/O
> requests and/or errors. When using modalias the module loading
> will be too late and the hooks will only be established after
> the probing has already happened.
> (The module autoloading is an asynchronous call in device_add(),
> where we don't write for it to succeed. So probing will continue
> and we woulnd't have the callbacks in place when probing
> starts).

Your analysis is correct.

But, the chicken-n-egg problem you described exists only for the first
device that is probed, module will be in place for the other devices.

The first device race is handled by acting on the bus notification for
the BUS_NOTIFY_BOUND_DRIVER event (patch 3/3 in my patch list).

>
> So adding the modalias will be of a purely informational value
> which I doubt is worth it.

Not true. I have tested this code, module gets inserted and the devices
come under the module as expected during device probing.

Please test it and let me know if you find it otherwise.
>
> Cheers,
>
> Hannes