Re: [PATCH vfs.all 15/26] s390/dasd: use bdev api in dasd_format()

[Al Viro <viro@zeniv.linux.org.uk>]

On Sun, Apr 28, 2024 at 07:58:23PM +0100, Al Viro wrote:
> On Wed, Apr 17, 2024 at 02:47:14PM +0200, Stefan Haberland wrote:
> 
> > set_blocksize() does basically also set i_blkbits like it was before.
> > The dasd_format ioctl does only work on a disabled device. To achieve this
> > all partitions need to be unmounted.
> > The tooling also refuses to work on disks actually in use.
> > 
> > So there should be no page cache to evict.
> 
> You mean this?
>         if (base->state != DASD_STATE_BASIC) {
>                 pr_warn("%s: The DASD cannot be formatted while it is enabled\n",
>                         dev_name(&base->cdev->dev));
>                 return -EBUSY;
>         }  
> 
> OK, but what would prevent dasd_ioctl_disable() from working while
> disk is in use?  And I don't see anything that would evict the
> page cache in dasd_ioctl_disable() either, actually...
> 
> What am I missing here?

BTW, you are updating block size according to new device size, before
        rc = base->discipline->format_device(base, fdata, 1);
	if (rc == -EAGAIN)
		rc = base->discipline->format_device(base, fdata, 0);
Unless something very unidiomatic is going on, this attempt to
format might fail...