linux-kernel - Re: [PATCH v4 2/3] mmc: core: Factor out the alignment of erase size

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Message-ID: <CAMz4kuJzqyAEam3RNJga5EERMh6TgXWFoY-uZ8pbm1OZW7uy8g@mail.gmail.com>
Date:   Tue, 6 Sep 2016 14:26:06 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Andreas Mohr <andi@...as.de>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Douglas 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>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v4 2/3] mmc: core: Factor out the alignment of erase size

Hi Andreas,

On 6 September 2016 at 12:34, Andreas Mohr <andi@...as.de> wrote:
> On Tue, Sep 06, 2016 at 10:55:11AM +0800, Baolin Wang wrote:
>> In order to clean up the mmc_erase() function and do some optimization
>> for erase size alignment, factor out the guts of erase size alignment
>> into mmc_align_erase_size() function.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>> Tested-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>  drivers/mmc/core/core.c |   60 +++++++++++++++++++++++++++++------------------
>>  1 file changed, 37 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 7d7209d..5f93eef 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -2202,6 +2202,37 @@ out:
>>       return err;
>>  }
>>
>> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
>> +                                      unsigned int *from,
>> +                                      unsigned int *to,
>> +                                      unsigned int nr)
>> +{
>> +     unsigned int from_new = *from, nr_new = nr, rem;
>> +
>> +     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
>> @@ -2234,31 +2265,14 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>>       }
>>
>>       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;
>> +             nr = mmc_align_erase_size(card, &from, &to, nr);
>> +             if (nr == 0)
>> +                     return 0;
>> +     } else {
>> +             /* 'from' and 'to' are inclusive */
>> +             to -= 1;
>>       }
>>
>> -     if (nr == 0)
>> -             return 0;
>> -
>> -     to = from + nr;
>> -
>> -     if (to <= from)
>> -             return -EINVAL;
>
> Hmm, this is swallowing -EINVAL behaviour
> i.e., now possibly violating protocol?

I didn't see what situation will make variable 'to' is less than
'from' since I think variable 'nr' is always larger than 0, right? If
so, we should remove this useless checking. Thanks.

>
> (this may easily be ok - haven't done an extensive review -
> but since the commit has that characteristic change,
> the commit message should contain that detail)
>
> Thanks for the cleanup work & HTH,
>
> Andreas Mohr



-- 
Baolin.wang
Best Regards