Re: [PATCH 14/26] block: move the nonrot flag to queue_limits

On Mon, Jun 17, 2024 at 08:04:41AM +0200, Christoph Hellwig wrote:
> Use the chance to switch to defaulting to non-rotational and require
> the driver to opt into rotational, which matches the polarity of the
> sysfs interface.
[...]
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index cb1c86a6a3fb9d..6cddf5baffe02a 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1867,11 +1867,6 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
>  		goto out_err_disk;
>  	}
>  
> -	/*
> -	 * Tell the block layer that we are not a rotational device
> -	 */
> -	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
> -
>  	mutex_init(&nbd->config_lock);
>  	refcount_set(&nbd->config_refs, 0);
>  	/*

NBD actually exports a flag for rotational devices; it's defined in
nbd.h in the NBD userland source as

#define NBD_FLAG_ROTATIONAL     (1 << 4)        /* Use elevator algorithm - rotational media */

which is passed in the same flags field which also contains the
NBD_FLAG_SEND_FLUSH and NBD_FLAG_SEND_FUA flags.

Perhaps we might want to look at that flag and set the device to
rotational if it is specified?

-- 
     w@uter.{be,co.za}
wouter@{grep.be,fosdem.org,debian.org}

I will have a Tin-Actinium-Potassium mixture, thanks.