Re: [PATCH v3 2/2] block: use blk_mq_plug() wrapper consistently in the block layer

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 9/29/22 16:47, Pankaj Raghav wrote:
> Use blk_mq_plug() wrapper to get the plug instead of directly accessing
> it in the block layer.
> 
> Either of the changes should not have led to a bug in zoned devices:
> 
> - blk_execute_rq_nowait:
>   Only passthrough requests can use this function, and plugging can be
>   performed on those requests in zoned devices. So no issues directly
>   accessing the plug.
> 
> - blk_flush_plug in bio_poll:
>   As we don't plug the requests that require a zone lock in the first
>   place, flushing should not have any impact. So no issues directly
>   accessing the plug.
> 
> This is just a cleanup patch to use this wrapper to get the plug
> consistently across the block layer.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>

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


> ---
>  block/blk-core.c | 2 +-
>  block/blk-mq.c   | 6 ++++--
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 203be672da52..d0e97de216db 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -850,7 +850,7 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
>  	    !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
>  		return 0;
>  
> -	blk_flush_plug(current->plug, false);
> +	blk_flush_plug(blk_mq_plug(bio), false);
>  
>  	if (bio_queue_enter(bio))
>  		return 0;
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index c11949d66163..5bf245c4bf0a 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1209,12 +1209,14 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
>   */
>  void blk_execute_rq_nowait(struct request *rq, bool at_head)
>  {
> +	struct blk_plug *plug = blk_mq_plug(rq->bio);
> +
>  	WARN_ON(irqs_disabled());
>  	WARN_ON(!blk_rq_is_passthrough(rq));
>  
>  	blk_account_io_start(rq);
> -	if (current->plug)
> -		blk_add_rq_to_plug(current->plug, rq);
> +	if (plug)
> +		blk_add_rq_to_plug(plug, rq);
>  	else
>  		blk_mq_sched_insert_request(rq, at_head, true, false);
>  }

-- 
Damien Le Moal
Western Digital Research