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Date: Fri, 2 Sep 2016 11:43:08 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Baolin Wang <baolin.wang@...aro.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
Russell King <rmk+kernel@....linux.org.uk>,
Shawn Lin <shawn.lin@...k-chips.com>,
Doug Anderson <dianders@...omium.org>,
Heiko Stübner <heiko@...ech.de>,
David Jander <david@...tonic.nl>,
Hans de Goede <hdegoede@...hat.com>,
linux-mmc <linux-mmc@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Mark Brown <broonie@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3] mmc: core: Optimize the mmc erase size alignment
On 31 August 2016 at 11:32, Baolin Wang <baolin.wang@...aro.org> wrote:
> Before issuing mmc_erase() function, users always have checked if it can
> erase with mmc_can_erase/trim/discard() function, thus remove the redundant
> erase checking in mmc_erase() function.
>
> This patch also optimizes the erase start/end sector alignment with
> round_up()/round_down() function, when erase command is MMC_ERASE_ARG.
>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> ---
> Changes since v2:
> - Add nr checking and other optimization in mmc_erase() function.
>
> Changes since v1:
> - Add the alignment if card->erase_size is not power of 2.
> ---
> drivers/mmc/core/core.c | 82 ++++++++++++++++++++++++++++++-----------------
> 1 file changed, 53 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index e55cde6..52156d4 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2202,6 +2202,51 @@ out:
> return err;
> }
>
> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
> + unsigned int *from,
> + unsigned int *to,
> + unsigned int nr)
> +{
How about make one patch that starts by moving the existing code into
a separate function, then on top as a new change, start playing with
the optimizations!?
That would be more easy to review.
> + unsigned int from_new = *from, nr_new = nr, rem;
> +
> + if (is_power_of_2(card->erase_size)) {
I would like some comment in the code, to understand what/why we do this.
> + unsigned int temp = from_new;
> +
> + from_new = round_up(temp, card->erase_size);
> + rem = from_new - temp;
> +
> + if (nr_new > rem)
> + nr_new -= rem;
> + else
> + return 0;
> +
> + nr_new = round_down(nr_new, card->erase_size);
> + } else {
Ditto.
> + rem = from_new % card->erase_size;
> + if (rem) {
> + rem = card->erase_size - rem;
> + from_new += rem;
> + if (nr_new > rem)
> + nr_new -= rem;
> + else
> + return 0;
> + }
> +
> + rem = nr_new % card->erase_size;
> + if (rem)
> + nr_new -= rem;
> + }
> +
> + if (nr_new == 0)
> + return 0;
> +
> + /* 'from' and 'to' are inclusive */
> + *to = from_new + nr_new - 1;
> + *from = from_new;
> +
> + return nr_new;
> +}
> +
> /**
> * mmc_erase - erase sectors.
> * @card: card to erase
> @@ -2217,13 +2262,6 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> unsigned int rem, to = from + nr;
> int err;
>
> - if (!(card->host->caps & MMC_CAP_ERASE) ||
> - !(card->csd.cmdclass & CCC_ERASE))
> - return -EOPNOTSUPP;
> -
> - if (!card->erase_size)
> - return -EOPNOTSUPP;
> -
I agree with Shawn here, please try to have one patch taking care of
one thing. If we find out that things goes wrong later, then it's
easier to drop/revert a change which causes the regression.
Moreover, for the above particular change, I don't think you should
remove these validations, as this is an API being exported. You may
convert to use mmc_can_erase() though.
Regarding all the mmc erase related exported APIs, there are certainly
a need for some clean-ups. For example, I think too many APIs are
being exported and we could probably also restructure the code a bit
so it becomes more readable. Although, of course this deserves a
standalone clean-up series. :-)
> if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
> return -EOPNOTSUPP;
>
> @@ -2240,31 +2278,17 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> return -EINVAL;
> }
>
> - if (arg == MMC_ERASE_ARG) {
> - rem = from % card->erase_size;
> - if (rem) {
> - rem = card->erase_size - rem;
> - from += rem;
> - if (nr > rem)
> - nr -= rem;
> - else
> - return 0;
> - }
> - rem = nr % card->erase_size;
> - if (rem)
> - nr -= rem;
> - }
> -
> if (nr == 0)
> return 0;
>
> - to = from + nr;
> -
> - if (to <= from)
> - return -EINVAL;
> -
> - /* 'from' and 'to' are inclusive */
> - to -= 1;
> + if (arg == MMC_ERASE_ARG) {
> + nr = mmc_align_erase_size(card, &from, &to, nr);
> + if (nr == 0)
> + return 0;
> + } else {
> + /* 'from' and 'to' are inclusive */
> + to -= 1;
> + }
>
> /*
> * Special case where only one erase-group fits in the timeout budget:
> --
> 1.7.9.5
>
Kind regards
Uffe
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