Re [patch RFC] mm/slab: introduce KZALLOC_FREE() cleanup-ed allocation macro

From: Przemek Kitszel
Date: Thu Mar 21 2024 - 12:27:04 EST


> From: Jiri Pirko <jiri@xxxxxxxxxx>
>
> With introduction of __free() macro using cleanup infrastructure, it
> will very likely become quite common to see following pattern:
> type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
>
> To follow the CLASS() flow from cleanup.h, introduce a simple macro
> KZALLOC_FREE() to wrap this over and allow the same flow.
>
> Show an example usage in gpio-sim driver.
>
> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
> ---
> drivers/gpio/gpio-sim.c | 3 +--
> include/linux/slab.h | 3 +++
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
> index c4106e37e6db..997237b3d80c 100644
> --- a/drivers/gpio/gpio-sim.c
> +++ b/drivers/gpio/gpio-sim.c
> @@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
> {
> int id;
>
> - struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
> - GFP_KERNEL);
> + KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
> if (!dev)
> return ERR_PTR(-ENOMEM);
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index b5f5ee8308d0..baee6acd58d3 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
> return kmalloc(size, flags | __GFP_ZERO);
> }
>
> +#define KZALLOC_FREE(_type, var, _gfp_t) \
> + _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
> +

Nice, but I would rather see this wrapper in the cleanup.h file, that have all
of the rest of related stuff.

On top of that, I want to propose also a wrapper that is simpler in that it
does not allocate but just assigns null, with that in mind `_FREE` part of your
proposed name does not sound right.

Most of the similar functions that define or declare something are named
DEFINE_STH...

(Please CC me on any future version, I have to go, sorry).

> /**
> * kzalloc_node - allocate zeroed memory from a particular memory node.
> * @size: how many bytes of memory are required.
> --
> 2.44.0
>
>