Re: [PATCH 3/8] bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Wed May 20, 2026 at 7:50 PM EDT, Tejun Heo wrote:
> The existing kernel-side export of bpf_arena_alloc_pages is _non_sleepable
> only - it's used by the verifier to inline the kfunc when the call site is
> non-sleepable. There is no sleepable equivalent for kernel callers; the
> kfunc bpf_arena_alloc_pages itself is BPF-only.
>
> sched_ext needs sleepable kernel-side allocs for its arena pool init/grow
> paths. Add bpf_arena_alloc_pages_sleepable() mirroring the _non_sleepable
> wrapper but passing sleepable=true to arena_alloc_pages().
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>

> ---
>  include/linux/bpf.h |  8 ++++++++
>  kernel/bpf/arena.c  | 13 +++++++++++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 831996c411cf..64968ca6db51 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -679,6 +679,8 @@ int bpf_dynptr_from_file_sleepable(struct file *file, u32 flags,
>  void *bpf_arena_alloc_pages_non_sleepable(void *p__map, void *addr__ign, u32 page_cnt, int node_id,
>  					  u64 flags);
>  void bpf_arena_free_pages_non_sleepable(void *p__map, void *ptr__ign, u32 page_cnt);
> +void *bpf_arena_alloc_pages_sleepable(void *p__map, void *addr__ign, u32 page_cnt, int node_id,
> +				      u64 flags);
>  #else
>  static inline void *bpf_arena_alloc_pages_non_sleepable(void *p__map, void *addr__ign, u32 page_cnt,
>  							int node_id, u64 flags)
> @@ -689,6 +691,12 @@ static inline void *bpf_arena_alloc_pages_non_sleepable(void *p__map, void *addr
>  static inline void bpf_arena_free_pages_non_sleepable(void *p__map, void *ptr__ign, u32 page_cnt)
>  {
>  }
> +
> +static inline void *bpf_arena_alloc_pages_sleepable(void *p__map, void *addr__ign, u32 page_cnt,
> +						    int node_id, u64 flags)
> +{
> +	return NULL;
> +}
>  #endif
>  
>  extern const struct bpf_map_ops bpf_map_offload_ops;
> diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
> index 1c0b87ecc817..a811cf6170fa 100644
> --- a/kernel/bpf/arena.c
> +++ b/kernel/bpf/arena.c
> @@ -934,6 +934,19 @@ void *bpf_arena_alloc_pages_non_sleepable(void *p__map, void *addr__ign, u32 pag
>  
>  	return (void *)arena_alloc_pages(arena, (long)addr__ign, page_cnt, node_id, false);
>  }
> +
> +void *bpf_arena_alloc_pages_sleepable(void *p__map, void *addr__ign, u32 page_cnt,
> +				      int node_id, u64 flags)
> +{
> +	struct bpf_map *map = p__map;
> +	struct bpf_arena *arena = container_of(map, struct bpf_arena, map);
> +
> +	if (map->map_type != BPF_MAP_TYPE_ARENA || flags || !page_cnt)
> +		return NULL;
> +
> +	return (void *)arena_alloc_pages(arena, (long)addr__ign, page_cnt, node_id, true);
> +}
> +
>  __bpf_kfunc void bpf_arena_free_pages(void *p__map, void *ptr__ign, u32 page_cnt)
>  {
>  	struct bpf_map *map = p__map;