Re: [PATCH] block/blk-ioprio: Skip zoned writes that are not append operations

[Damien Le Moal <dlemoal@kernel.org>]

On 12/12/23 08:14, Bart Van Assche wrote:
> If REQ_OP_WRITE or REQ_OP_WRITE_ZEROES operations for the same zone
> originate from different cgroups that could result in different
> priorities being assigned to these operations. Do not modify the I/O
> priority of these write operations to prevent that these would be
> executed in the wrong order when using the mq-deadline I/O

...to prevent them from being executed in the wrong...

> scheduler.
> 
> Cc: Damien Le Moal <dlemoal@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/blk-ioprio.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
> index 4051fada01f1..09ce083a0e3a 100644
> --- a/block/blk-ioprio.c
> +++ b/block/blk-ioprio.c
> @@ -192,6 +192,17 @@ void blkcg_set_ioprio(struct bio *bio)
>  	if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
>  		return;
>  
> +	/*
> +	 * If REQ_OP_WRITE or REQ_OP_WRITE_ZEROES operations for the same zone
> +	 * originate from different cgroups that could result in different
> +	 * priorities being assigned to these operations. Do not modify the I/O
> +	 * priority of these write operations to prevent that these would be
> +	 * executed in the wrong order when using the mq-deadline I/O
> +	 * scheduler.
> +	 */
> +	if (bdev_op_is_zoned_write(bio->bi_bdev, bio_op(bio)))

Ideally, we want the bio equivalent of blk_rq_is_seq_zoned_write() here so that
writes to conventional zones are not affected (these can be reordered).

> +		return;
> +
>  	if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT ||
>  	    blkcg->prio_policy == POLICY_NONE_TO_RT) {
>  		/*

-- 
Damien Le Moal
Western Digital Research