Re: [PATCH v7 1/3] bio: limit bio max size

[Bart Van Assche <bvanassche@acm.org>]

On 4/12/21 7:55 PM, Changheun Lee wrote:
> +unsigned int bio_max_size(struct bio *bio)
> +{
> +	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
> +
> +	if (blk_queue_limit_bio_size(q))
> +		return blk_queue_get_max_sectors(q, bio_op(bio))
> +			<< SECTOR_SHIFT;
> +
> +	return UINT_MAX;
> +}

This patch adds an if-statement to the hot path and that may have a
slight negative performance impact. I recommend to follow the approach
of max_hw_sectors. That means removing QUEUE_FLAG_LIMIT_BIO_SIZE and to
initialize the maximum bio size to UINT_MAX in blk_set_default_limits().

Thanks,

Bart.