Re: [PATCH 1/2] mm/slab: Add kvfree_atomic() helper

Vlastimil Babka
2026-04-29T08:28:04Z

+Cc SLAB maintainers. Please use get_maintainers.pl next time.

On 4/28/26 18:14, Uladzislau Rezki (Sony) wrote:
> kvmalloc() now supports non-sleeping GFP flags, including
> the vmalloc fallback path. This means it may return vmalloc
> memory even for GFP_ATOMIC and GFP_NOWAIT allocations.
>
> Freeing such memory with kvfree() may then end up calling
> vfree(), which is not safe for non-sleeping contexts.
>
> Introduce kvfree_atomic() helper for such cases. It mirrors
> kvfree(), but uses vfree_atomic() for vmalloced memory.
>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

> ---
> include/linux/slab.h | 3 +++
> mm/slub.c | 16 ++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 15a60b501b95..2b5ab488e96b 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -1234,6 +1234,9 @@ void *kvrealloc_node_align_noprof(const void *p, size_t size, unsigned long alig
> extern void kvfree(const void *addr);
> DEFINE_FREE(kvfree, void *, if (!IS_ERR_OR_NULL(_T)) kvfree(_T))
>
> +extern void kvfree_atomic(const void *addr);
> +DEFINE_FREE(kvfree_atomic, void *, if (!IS_ERR_OR_NULL(_T)) kvfree_atomic(_T))
> +
> extern void kvfree_sensitive(const void *addr, size_t len);
>
> unsigned int kmem_cache_size(struct kmem_cache *s);
> diff --git a/mm/slub.c b/mm/slub.c
> index 2b2d33cc735c..b096677c8152 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -6802,6 +6802,22 @@ void kvfree(const void *addr)
> }
> EXPORT_SYMBOL(kvfree);
>
> +/**
> + * kvfree_atomic() - Free memory.
> + * @addr: Pointer to allocated memory.
> + *
> + * Same as kvfree(), but uses vfree_atomic() for vmalloc
> + * backed memory. Must not be called from NMI context.
> + */
> +void kvfree_atomic(const void *addr)
> +{
> + if (is_vmalloc_addr(addr))
> + vfree_atomic(addr);
> + else
> + kfree(addr);
> +}
> +EXPORT_SYMBOL(kvfree_atomic);
> +
> /**
> * kvfree_sensitive - Free a data object containing sensitive information.
> * @addr: address of the data object to be freed.