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

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Date:   Tue, 6 Sep 2016 16:27:25 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Andreas Mohr <andi@...as.de>, Ulf Hansson <ulf.hansson@...aro.org>,
        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

On 6 September 2016 at 15:52, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 6/09/2016 9:26 a.m., Baolin Wang wrote:
>>
>> 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.
>
>
> It is checking overflows.

Yes, you are right, my mistake. I will add this checking in next version.

>
>>
>>>
>>> (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
>>
>>
>>
>>
> --
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-- 
Baolin.wang
Best Regards