linux-kernel - Re: [PATCH 3/3] mmc: block: Requeue on block size restrictions

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Date:   Fri, 18 Nov 2022 13:34:25 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Christian Löhle <CLoehle@...erstone.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Cc:     Avri Altman <Avri.Altman@....com>,
        "vincent.whitchurch@...s.com" <vincent.whitchurch@...s.com>
Subject: Re: [PATCH 3/3] mmc: block: Requeue on block size restrictions

On 26/10/22 10:30, Christian Löhle wrote:
> The block layer does not conform to all our sector count restrictions, so
> requeue in case we had to modify the number of blocks sent instead of
> going through the normal completion.
> 
> Note that the normal completion used before does not lead to a bug,
> this change is just the nicer thing to do.

Can you elaborate on why it is "nicer"?

> An example of such a restriction is max_blk_count = 1 and 512 blksz,
> but the block layer continues to use requests of size PAGE_SIZE.
> 
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>
> ---
>  drivers/mmc/core/block.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 54cd009aee50..c434d3964880 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -1519,8 +1519,10 @@ static void mmc_blk_cqe_req_done(struct mmc_request *mrq)
>  	/*
>  	 * Block layer timeouts race with completions which means the normal
>  	 * completion path cannot be used during recovery.
> +	 * Also do not use it if we had to modify the block count to satisfy
> +	 * host controller needs.
>  	 */
> -	if (mq->in_recovery)
> +	if (mq->in_recovery || mrq->data->blocks != blk_rq_sectors(req))
>  		mmc_blk_cqe_complete_rq(mq, req);
>  	else if (likely(!blk_should_fake_timeout(req->q)))
>  		blk_mq_complete_request(req);
> @@ -2051,8 +2053,10 @@ static void mmc_blk_hsq_req_done(struct mmc_request *mrq)
>  	/*
>  	 * Block layer timeouts race with completions which means the normal
>  	 * completion path cannot be used during recovery.
> +	 * Also do not use it if we had to modify the block count to satisfy
> +	 * host controller needs.
>  	 */
> -	if (mq->in_recovery)
> +	if (mq->in_recovery || mrq->data->blocks != blk_rq_sectors(req))
>  		mmc_blk_cqe_complete_rq(mq, req);
>  	else if (likely(!blk_should_fake_timeout(req->q)))
>  		blk_mq_complete_request(req);
> @@ -2115,8 +2119,10 @@ static void mmc_blk_mq_post_req(struct mmc_queue *mq, struct request *req,
>  	/*
>  	 * Block layer timeouts race with completions which means the normal
>  	 * completion path cannot be used during recovery.
> +	 * Also do not use it if we had to modify the block count to satisfy
> +	 * host controller needs.
>  	 */
> -	if (mq->in_recovery) {
> +	if (mq->in_recovery || mrq->data->blocks != blk_rq_sectors(req)) {
>  		mmc_blk_mq_complete_rq(mq, req);
>  	} else if (likely(!blk_should_fake_timeout(req->q))) {
>  		if (can_sleep)