On 3 June 2015 at 10:34, David Jander <david@xxxxxxxxxxx> wrote:
> In the (not so unlikely) case that the mmc controller timeout budget is
> enough for exactly one erase-group, the simplification of allowing one
> sector has an enormous performance penalty. We optimize this special case
> by introducing a flag that prohibits erase-group boundary crossing, so
> that we can allow trimming more than one sector at a time.
>
> Signed-off-by: David Jander <david@xxxxxxxxxxx>
Hi David,
Thanks for working on this!
> ---
> drivers/mmc/core/core.c | 21 +++++++++++++++++----
> include/linux/mmc/card.h | 1 +
> 2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 92e7671..6c9611b 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2089,6 +2089,7 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> unsigned int arg)
> {
> unsigned int rem, to = from + nr;
> + int err;
>
> if (!(card->host->caps & MMC_CAP_ERASE) ||
> !(card->csd.cmdclass & CCC_ERASE))
> @@ -2139,6 +2140,15 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> /* 'from' and 'to' are inclusive */
> to -= 1;
>
> + if ((arg & MMC_TRIM_ARGS) && (card->eg_boundary) &&
> + (from % card->erase_size)) {
> + rem = card->erase_size - (from % card->erase_size);
> + err = mmc_do_erase(card, from, from + rem - 1, arg);
> + from += rem;
> + if ((err) || (to <= from))
> + return err;
> + }
> +
Urgh, this function is becoming a bit messy. Would it be possible to
split the code into some helper functions instead - and adding some
additional comments of what goes on maybe?
> return mmc_do_erase(card, from, to, arg);
> }
> EXPORT_SYMBOL(mmc_erase);
> @@ -2234,16 +2244,19 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
> if (!qty)
> return 0;
>
> + /* We can only erase one erase group special case */
Could you extend this comment a bit. I think it deserves that.
> if (qty == 1)
> - return 1;
> + card->eg_boundary = 1;
> + else
> + qty--;
>
> /* Convert qty to sectors */
> if (card->erase_shift)
> - max_discard = --qty << card->erase_shift;
> + max_discard = qty << card->erase_shift;
> else if (mmc_card_sd(card))
> - max_discard = qty;
> + max_discard = qty + 1;
> else
> - max_discard = --qty * card->erase_size;
> + max_discard = qty * card->erase_size;
>
> return max_discard;
> }
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 19f0175..704b60d 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -282,6 +282,7 @@ struct mmc_card {
> unsigned int erase_size; /* erase size in sectors */
> unsigned int erase_shift; /* if erase unit is power 2 */
> unsigned int pref_erase; /* in sectors */
> + unsigned int eg_boundary; /* don't cross erase-group boundaries */
> u8 erased_byte; /* value of erased bytes */
>
> u32 raw_cid[4]; /* raw card CID */
> --
> 2.1.4
>
Kind regards
Uffe
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