[1/2] pinctrl: pinconf-generic: resize the pin config array directly

  pinconf_generic_parse_dt_config() allocates memory that is large enough
to contain all the config parameters. Then, kmemdup() copies the found
configs to the memory with the exact size.

There is no need to allocate memory twice; you can directly resize the
initial memory using krealloc_array().

I also changed kcalloc() to kmalloc_array() to keep the consistency with
krealloc_array(). This change has no impact because you do not need to
zero out the 'cfg' array.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 drivers/pinctrl/pinconf-generic.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)
  

On Tue, Nov 21, 2023 at 7:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> pinconf_generic_parse_dt_config() allocates memory that is large enough
> to contain all the config parameters. Then, kmemdup() copies the found
> configs to the memory with the exact size.
>
> There is no need to allocate memory twice; you can directly resize the
> initial memory using krealloc_array().
>
> I also changed kcalloc() to kmalloc_array() to keep the consistency with
> krealloc_array(). This change has no impact because you do not need to
> zero out the 'cfg' array.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>



Sorry, I retract this patch set.

krealloc() does not save any memory
when the new_size is smaller than the current size.













> ---
>
>  drivers/pinctrl/pinconf-generic.c | 25 ++++++++-----------------
>  1 file changed, 8 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/pinctrl/pinconf-generic.c b/drivers/pinctrl/pinconf-generic.c
> index 8313cb5f3b3c..ba4fe2466e78 100644
> --- a/drivers/pinctrl/pinconf-generic.c
> +++ b/drivers/pinctrl/pinconf-generic.c
> @@ -247,7 +247,6 @@ int pinconf_generic_parse_dt_config(struct device_node *np,
>  {
>         unsigned long *cfg;
>         unsigned int max_cfg, ncfg = 0;
> -       int ret;
>
>         if (!np)
>                 return -EINVAL;
> @@ -256,7 +255,7 @@ int pinconf_generic_parse_dt_config(struct device_node *np,
>         max_cfg = ARRAY_SIZE(dt_params);
>         if (pctldev)
>                 max_cfg += pctldev->desc->num_custom_params;
> -       cfg = kcalloc(max_cfg, sizeof(*cfg), GFP_KERNEL);
> +       cfg = kmalloc_array(max_cfg, sizeof(*cfg), GFP_KERNEL);
>         if (!cfg)
>                 return -ENOMEM;
>
> @@ -266,30 +265,22 @@ int pinconf_generic_parse_dt_config(struct device_node *np,
>                 parse_dt_cfg(np, pctldev->desc->custom_params,
>                              pctldev->desc->num_custom_params, cfg, &ncfg);
>
> -       ret = 0;
> -
>         /* no configs found at all */
>         if (ncfg == 0) {
> +               kfree(cfg);
>                 *configs = NULL;
>                 *nconfigs = 0;
> -               goto out;
> +               return 0;
>         }
>
> -       /*
> -        * Now limit the number of configs to the real number of
> -        * found properties.
> -        */
> -       *configs = kmemdup(cfg, ncfg * sizeof(unsigned long), GFP_KERNEL);
> -       if (!*configs) {
> -               ret = -ENOMEM;
> -               goto out;
> -       }
> +       /* Now resize the array to store the real number of found properties. */
> +       *configs = krealloc_array(cfg, ncfg, sizeof(unsigned long), GFP_KERNEL);
> +       if (!*configs)
> +               return -ENOMEM;
>
>         *nconfigs = ncfg;
>
> -out:
> -       kfree(cfg);
> -       return ret;
> +       return 0;
>  }
>  EXPORT_SYMBOL_GPL(pinconf_generic_parse_dt_config);
>
> --
> 2.40.1
>
  

Hi Masahiro,

On Tue, Nov 21, 2023 at 11:21 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> On Tue, Nov 21, 2023 at 7:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > pinconf_generic_parse_dt_config() allocates memory that is large enough
> > to contain all the config parameters. Then, kmemdup() copies the found
> > configs to the memory with the exact size.
> >
> > There is no need to allocate memory twice; you can directly resize the
> > initial memory using krealloc_array().
> >
> > I also changed kcalloc() to kmalloc_array() to keep the consistency with
> > krealloc_array(). This change has no impact because you do not need to
> > zero out the 'cfg' array.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
> Sorry, I retract this patch set.
>
> krealloc() does not save any memory
> when the new_size is smaller than the current size.

But the first part where you switch to kmalloc_array() is still a nice change.

The fact that we use kmemdup to be able to also shrink the allocation is a
bit of an oddity I guess, but let's run this patch by Andy Shevchenko, and
ask what he thinks about simply introducing kmemdup_array() or if he
has other ideas for this.

Yours,
Linus Walleij
  

On Fri, Nov 24, 2023 at 11:06:50AM +0100, Linus Walleij wrote:
> On Tue, Nov 21, 2023 at 11:21 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > On Tue, Nov 21, 2023 at 7:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > >
> > > pinconf_generic_parse_dt_config() allocates memory that is large enough
> > > to contain all the config parameters. Then, kmemdup() copies the found
> > > configs to the memory with the exact size.
> > >
> > > There is no need to allocate memory twice; you can directly resize the
> > > initial memory using krealloc_array().
> > >
> > > I also changed kcalloc() to kmalloc_array() to keep the consistency with
> > > krealloc_array(). This change has no impact because you do not need to
> > > zero out the 'cfg' array.
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >
> > Sorry, I retract this patch set.
> >
> > krealloc() does not save any memory
> > when the new_size is smaller than the current size.
> 
> But the first part where you switch to kmalloc_array() is still a nice change.
> 
> The fact that we use kmemdup to be able to also shrink the allocation is a
> bit of an oddity I guess, but let's run this patch by Andy Shevchenko, and
> ask what he thinks about simply introducing kmemdup_array() or if he
> has other ideas for this.

https://lore.kernel.org/all/20231017052322.2636-2-kkartik@nvidia.com/
  

On Fri, Nov 24, 2023 at 8:25 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Fri, Nov 24, 2023 at 11:06:50AM +0100, Linus Walleij wrote:
> > On Tue, Nov 21, 2023 at 11:21 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > > On Tue, Nov 21, 2023 at 7:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > > >
> > > > pinconf_generic_parse_dt_config() allocates memory that is large enough
> > > > to contain all the config parameters. Then, kmemdup() copies the found
> > > > configs to the memory with the exact size.
> > > >
> > > > There is no need to allocate memory twice; you can directly resize the
> > > > initial memory using krealloc_array().
> > > >
> > > > I also changed kcalloc() to kmalloc_array() to keep the consistency with
> > > > krealloc_array(). This change has no impact because you do not need to
> > > > zero out the 'cfg' array.
> > > >
> > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > >
> > > Sorry, I retract this patch set.
> > >
> > > krealloc() does not save any memory
> > > when the new_size is smaller than the current size.
> >
> > But the first part where you switch to kmalloc_array() is still a nice change.
> >
> > The fact that we use kmemdup to be able to also shrink the allocation is a
> > bit of an oddity I guess, but let's run this patch by Andy Shevchenko, and
> > ask what he thinks about simply introducing kmemdup_array() or if he
> > has other ideas for this.
>
> https://lore.kernel.org/all/20231017052322.2636-2-kkartik@nvidia.com/


Ok, I will come back when kmemdup_array() is upstreamed.



> --
> With Best Regards,
> Andy Shevchenko
>
>