[PATCH 06/10] dasd: implement ->set_read_only to hook into BLKROSET processing

[Stefan Haberland]

Christoph Hellwig <hch at lst.de> schrieb am Fri, 06. Nov 15:02:
> On Thu, Nov 05, 2020 at 09:56:47PM +0100, Stefan Haberland wrote:
> > > +	/* do not manipulate hardware state for partitions */
> > >  	if (bdev_is_partition(bdev))
> > > -		// ro setting is not allowed for partitions
> > > -		return -EINVAL;
> > > -	if (get_user(intval, (int __user *)argp))
> > > -		return -EFAULT;
> > > +		return 0;
> > > +
> > >  	base = dasd_device_from_gendisk(bdev->bd_disk);
> > >  	if (!base)
> > >  		return -ENODEV;
> > > -	if (!intval && test_bit(DASD_FLAG_DEVICE_RO, &base->flags)) {
> > > -		dasd_put_device(base);
> > > -		return -EROFS;
> > > -	}
> > > -	set_disk_ro(bdev->bd_disk, intval);
> > 
> > 
> > While testing this patch I just noticed that when I set a device readonly this is
> > not going to be passed on to the partitions on this device any longer.
> > 
> > This is caused by the removed call to set_disk_ro().
> > 
> > Is this intentional or was this removed by accident?
> 
> It was unintentionally intentional :)
> 
> The generic code used already by almost all drivers in mainline only
> calls set_device_ro from blkdev_roset, that is it only sets the main
> device read-only.  dasd was the outlier here, and I didn't notice it
> actually called set_disk_ro instead of set_device_ro.   That being
> said I think setting all the partitions read-only as well when the
> full device is set read-only makes perfect sense.  I'm just a little
> worried it could cause regressions.  Let me prepare a follow on patch
> on top of the series that switches to that behavior.

Makes sense.
I am fine with that.

With this in mind:

Reviewed-by: Stefan Haberland <sth at linux.ibm.com>