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

Christoph Hellwig
2020-11-06T14:02:06Z

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.