linux-kernel - Re: [PATCH 2/5] iio: adc: xilinx: use devm_krealloc() instead of kfree() + kcalloc()

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Message-ID: <CAHp75Vf-z8yba-QX4G51PRkMV9VKAczd_79sma96zHRf+bMD2w@mail.gmail.com>
Date:   Tue, 27 Oct 2020 12:30:41 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Michal Simek <michal.simek@...inx.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 2/5] iio: adc: xilinx: use devm_krealloc() instead of
 kfree() + kcalloc()

On Tue, Oct 27, 2020 at 12:04 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> On Tue, Oct 27, 2020 at 10:33 AM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> >
> > On Mon, Oct 26, 2020 at 4:03 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> > >
> > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > >
> > > We now have devm_krealloc() in the kernel Use it indstead of calling
> > > kfree() and kcalloc() separately.
> >
> > Which is completely lawful when size > previous_size (I mean, the
> > additional patch you sent previously seems not related to this).
> >
>
> Sure but devm_krealloc() is cleaner and adds the benefit of resource management.

I meant devm_krealloc(). It should work in this case without your
additional "fix" patch.

> > > -       kfree(xadc->data);
> > > -       xadc->data = kcalloc(n, sizeof(*xadc->data), GFP_KERNEL);
> > > +       xadc->data = devm_krealloc(indio_dev->dev.parent, xadc->data,
> > > +                                  n * sizeof(*xadc->data),
> >
> > I think you need to use something from overflow.h instead of explicit
> > multiplication here.
> >
>
> Or maybe add devm_krealloc_array() which would perform the checks
> behind the scenes?

Maybe. But what to do in the cases when you have struct with flexible
arrays, like
struct foo {
...
 type bar[];
};

?

And you do kzalloc(sizeof(foo)) followed by krealloc(). The above name
(krealloc_array) may be a bit ambiguous.

> > > +                                  GFP_KERNEL | __GFP_ZERO);

-- 
With Best Regards,
Andy Shevchenko