Re: [RFC PATCH v4 3/3] bcache: reject writeback cache mode for zoned backing device

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2020/05/22 21:19, Coly Li wrote:
> Currently we don't support writeback mode for zoned device as backing
> device. So reject it by sysfs interface.
> 
> This rejection will be removed after the writeback cache mode support
> for zoned device gets done.
> 
> Signed-off-by: Coly Li <colyli@suse.de>
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  drivers/md/bcache/sysfs.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
> index 323276994aab..41bdbc42a17d 100644
> --- a/drivers/md/bcache/sysfs.c
> +++ b/drivers/md/bcache/sysfs.c
> @@ -359,6 +359,11 @@ STORE(__cached_dev)
>  		if (v < 0)
>  			return v;
>  
> +		if ((unsigned int) v == CACHE_MODE_WRITEBACK) {
> +			pr_err("writeback mode is not supported for zoned backing device.\n");
> +			return -ENOTSUPP;
> +		}
> +
>  		if ((unsigned int) v != BDEV_CACHE_MODE(&dc->sb)) {
>  			SET_BDEV_CACHE_MODE(&dc->sb, v);
>  			bch_write_bdev_super(dc, NULL);
> 

Do you have a similar check in bcache user tools at format time ? Or is the
cache mode specified only when the bcache device is started ?

Looks good.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital Research