linux-kernel - Re: [PATCHv4 1/2] mmc: block: Remove error check of hw

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Date:   Thu, 13 Oct 2022 13:37:55 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Christian Löhle <CLoehle@...erstone.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv4 1/2] mmc: block: Remove error check of hw_reset on reset

On 12/10/22 21:37, Christian Löhle wrote:
> Before switching back to the right partition in mmc_blk_reset there used
> to be a check if hw_reset was even supported. This return value
> was removed, so there is no reason to check. Furthermore ensure
> part_curr is not falsely set to a valid value on reset or
> partition switch error.
> 
> As part of this change the code paths of mmc_blk_reset calls were checked
> to ensure no commands are issued after a failed mmc_blk_reset directly
> without going through the block layer.
> 
> Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in mmc_hw|sw_reset()")
> Cc: stable@...r.kernel.org
> 
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>

One minor comment, otherwise:

Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
> -v4: Only partition switch if necessary and fix one mmc_blk_reset call
> -v3: Ensure invalid part_curr on error
> -v2: Do not attempt to switch partitions if reset failed
> 
>  drivers/mmc/core/block.c | 42 ++++++++++++++++++++++++----------------
>  1 file changed, 25 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index ce89611a136e..2619cc47b97c 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -134,6 +134,7 @@ struct mmc_blk_data {
>  	 * track of the current selected device partition.
>  	 */
>  	unsigned int	part_curr;
> +#define MMC_BLK_PART_INVALID	UINT_MAX	/* Unknown partition active */
>  	int	area_type;
>  
>  	/* debugfs files (only in main mmc_blk_data) */
> @@ -987,33 +988,39 @@ static unsigned int mmc_blk_data_timeout_ms(struct mmc_host *host,
>  	return ms;
>  }
>  
> +/*
> + * Attempts to reset the card and get back to the requested partition.
> + * Therefore any error here must result in cancelling the block layer
> + * request, it must not be reattempted without going through the mmc_blk
> + * partition sanity checks.
> + */
>  static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
>  			 int type)
>  {
>  	int err;
> +	struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
>  
>  	if (md->reset_done & type)
>  		return -EEXIST;
>  
>  	md->reset_done |= type;
>  	err = mmc_hw_reset(host->card);
> +	/*
> +	 * A successful reset will leave the card in the main partition, but
> +	 * upon failure it might not be, so set it to MMC_BLK_PART_INVALID
> +	 * in that case.
> +	 */
> +	main_md->part_curr = err ? MMC_BLK_PART_INVALID : main_md->part_type;
> +	if (err)
> +		return err;
>  	/* Ensure we switch back to the correct partition */
> -	if (err) {
> -		struct mmc_blk_data *main_md =
> -			dev_get_drvdata(&host->card->dev);
> -		int part_err;
> -
> -		main_md->part_curr = main_md->part_type;
> -		part_err = mmc_blk_part_switch(host->card, md->part_type);
> -		if (part_err) {
> -			/*
> -			 * We have failed to get back into the correct
> -			 * partition, so we need to abort the whole request.
> -			 */
> -			return -ENODEV;
> -		}
> -	}
> -	return err;
> +	if (mmc_blk_part_switch(host->card, md->part_type))
> +		/*
> +		 * We have failed to get back into the correct
> +		 * partition, so we need to abort the whole request.
> +		 */
> +		return -ENODEV;
> +	return 0;
>  }
>  
>  static inline void mmc_blk_reset_success(struct mmc_blk_data *md, int type)
> @@ -1868,7 +1875,8 @@ static void mmc_blk_mq_rw_recovery(struct mmc_queue *mq, struct request *req)
>  
>  	/* Reset before last retry */
>  	if (mqrq->retries + 1 == MMC_MAX_RETRIES)
> -		mmc_blk_reset(md, card->host, type);
> +		if (mmc_blk_reset(md, card->host, type))

Kernel style is to avoid nested "if" statements, so it should be like this:

  	if (mqrq->retries + 1 == MMC_MAX_RETRIES &&
	    mmc_blk_reset(md, card->host, type)
		return;

> +			return;
>  
>  	/* Command errors fail fast, so use all MMC_MAX_RETRIES */
>  	if (brq->sbc.error || brq->cmd.error)