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

[Adrian Hunter]

On 6/09/2016 9:26 a.m., Baolin Wang wrote:
> Hi Andreas,
>
> On 6 September 2016 at 12:34, Andreas Mohr <andi@xxxxxxxx> 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@xxxxxxxxxx>
> > > Tested-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> > > ---
> > >   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.

> > (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