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

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

On Sat, Apr 06, 2024 at 05:09:19PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Avoid to access bd_inode directly, prepare to remove bd_inode from
> block_devcie.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
>  drivers/s390/block/dasd_ioctl.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
> index 7e0ed7032f76..c1201590f343 100644
> --- a/drivers/s390/block/dasd_ioctl.c
> +++ b/drivers/s390/block/dasd_ioctl.c
> @@ -215,8 +215,9 @@ dasd_format(struct dasd_block *block, struct format_data_t *fdata)
>  	 * enabling the device later.
>  	 */
>  	if (fdata->start_unit == 0) {
> -		block->gdp->part0->bd_inode->i_blkbits =
> -			blksize_bits(fdata->blksize);
> +		rc = set_blocksize(block->gdp->part0, fdata->blksize);

Could somebody (preferably s390 folks) explain what is going on in
dasd_format()?  The change in this commit is *NOT* an equivalent
transformation - mainline does not evict the page cache of device.

Is that
	* intentional behaviour in mainline version, possibly broken
by this patch
	* a bug in mainline accidentally fixed by this patch
	* something else?

And shouldn't there be an exclusion between that and having a filesystem
on a partition of that disk currently mounted?