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Date: Mon, 5 Sep 2016 16:27:35 +0800
From: Baolin Wang <baolin.wang@...aro.org>
To: Ulf Hansson <ulf.hansson@...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
Hi Ulf,
On 2 September 2016 at 17:43, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> 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.
Make sense. I'll do what you suggested in next version.
>
>> + 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.
I think the erase_size is power of 2 in most cases, then the
round_up/down() is more efficient than '%' operation. I'll add some
comments to explain that.
>
>> + 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.
OK.
>
> 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.
These validations are redundant, since we always have checked if it
can erase with mmc_can_erase/trim/discard() function before issuing
mmc_erase(). Another hand these validations should be moved into
mmc_can_erase() not in mmc_erase() function.
>
> 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. :-)
OK. I would like to do some clean up for erase function after this
optimization. Thanks for your comments.
>
>> 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
--
Baolin.wang
Best Regards
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