[RFC PATCH 3/9] bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers

[Tejun Heo <tj@kernel.org>]

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>
---
 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 0136a108d083..af54705611d7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -678,6 +678,8 @@ 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)
@@ -688,6 +690,12 @@ 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 4e480c2f3786..73e43617761c 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -947,6 +947,19 @@ 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;
-- 
2.53.0