On 9/5/24 9:56 AM, Christian Brauner wrote:
> Use _Generic() to create a compatibility layer that type switches on the
> third argument to either call __kmem_cache_create() or
> __kmem_cache_create_args(). If NULL is passed for the struct
> kmem_cache_args argument use default args making porting for callers
> that don't care about additional arguments easy.
>
> Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> ---
> include/linux/slab.h | 29 ++++++++++++++++++++++++++---
> mm/slab_common.c | 10 +++++-----
> 2 files changed, 31 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index cb264dded324..f74ceb788ac1 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -261,9 +261,10 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
> unsigned int object_size,
> struct kmem_cache_args *args,
> slab_flags_t flags);
> -struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
> - unsigned int align, slab_flags_t flags,
> - void (*ctor)(void *));
> +
> +struct kmem_cache *__kmem_cache_create(const char *name, unsigned int size,
> + unsigned int align, slab_flags_t flags,
> + void (*ctor)(void *));
> struct kmem_cache *kmem_cache_create_usercopy(const char *name,
> unsigned int size, unsigned int align,
> slab_flags_t flags,
> @@ -272,6 +273,28 @@ struct kmem_cache *kmem_cache_create_usercopy(const char *name,
> struct kmem_cache *kmem_cache_create_rcu(const char *name, unsigned int size,
> unsigned int freeptr_offset,
> slab_flags_t flags);
> +
> +/* If NULL is passed for @args, use this variant with default arguments. */
> +static inline struct kmem_cache *
> +__kmem_cache_default_args(const char *name, unsigned int size,
> + struct kmem_cache_args *args,
> + slab_flags_t flags)
> +{
> + struct kmem_cache_args kmem_default_args = {};
> +
> + /* Make sure we don't get passed garbage. */
> + if (WARN_ON_ONCE(args))
> + return NULL;
I'm changing to return ERR_PTR(-EINVAL); locally
although it's not too important
> +
> + return __kmem_cache_create_args(name, size, &kmem_default_args, flags);
> +}
> +
> +#define kmem_cache_create(__name, __object_size, __args, ...) \
> + _Generic((__args), \
> + struct kmem_cache_args *: __kmem_cache_create_args, \
> + void *: __kmem_cache_default_args, \
> + default: __kmem_cache_create)(__name, __object_size, __args, __VA_ARGS__)
> +
> void kmem_cache_destroy(struct kmem_cache *s);
> int kmem_cache_shrink(struct kmem_cache *s);
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 19ae3dd6e36f..418459927670 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -383,7 +383,7 @@ kmem_cache_create_usercopy(const char *name, unsigned int size,
> EXPORT_SYMBOL(kmem_cache_create_usercopy);
>
> /**
> - * kmem_cache_create - Create a cache.
> + * __kmem_cache_create - Create a cache.
> * @name: A string which is used in /proc/slabinfo to identify this cache.
> * @size: The size of objects to be created in this cache.
> * @align: The required alignment for the objects.
> @@ -407,9 +407,9 @@ EXPORT_SYMBOL(kmem_cache_create_usercopy);
> *
> * Return: a pointer to the cache on success, NULL on failure.
> */
> -struct kmem_cache *
> -kmem_cache_create(const char *name, unsigned int size, unsigned int align,
> - slab_flags_t flags, void (*ctor)(void *))
> +struct kmem_cache *__kmem_cache_create(const char *name, unsigned int size,
> + unsigned int align, slab_flags_t flags,
> + void (*ctor)(void *))
> {
> struct kmem_cache_args kmem_args = {
> .align = align,
> @@ -418,7 +418,7 @@ kmem_cache_create(const char *name, unsigned int size, unsigned int align,
>
> return __kmem_cache_create_args(name, size, &kmem_args, flags);
> }
> -EXPORT_SYMBOL(kmem_cache_create);
> +EXPORT_SYMBOL(__kmem_cache_create);
>
> /**
> * kmem_cache_create_rcu - Create a SLAB_TYPESAFE_BY_RCU cache.
>
