linux-kernel - Re: [PATCH v4] mmc: core: don't set limits.discard

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Message-ID: <yq1pn60g5r4.fsf@ca-mkp.ca.oracle.com>
Date:   Fri, 02 Oct 2020 08:57:09 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Coly Li <colyli@...e.de>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, Vicente Bergas <vicencb@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v4] mmc: core: don't set limits.discard_granularity as 0


Coly,

> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index 6c022ef0f84d..350d0cc4ee62 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -190,7 +190,7 @@ static void mmc_queue_setup_discard(struct request_queue *q,
>  	q->limits.discard_granularity = card->pref_erase << 9;
>  	/* granularity must not be greater than max. discard */
>  	if (card->pref_erase > max_discard)
> -		q->limits.discard_granularity = 0;
> +		q->limits.discard_granularity = SECTOR_SIZE;
>  	if (mmc_can_secure_erase_trim(card))
>  		blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
>  }

The granularity should probably be set to the logical block size instead
of SECTOR_SIZE. However, looking at mmc_setup_queue() it doesn't appear
the logical block size is read from the CSD until after discard has been
configured. So that will require a bit of code shuffling.

-- 
Martin K. Petersen	Oracle Linux Engineering