[PATCH v2 bpf-next 6/7] bpf: Allows per-cpu maps and map-in-map in sleepable programs

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

Since sleepable programs are now executing under migrate_disable
the per-cpu maps are safe to use.
The map-in-map were ok to use in sleepable from the time sleepable
progs were introduced.

Note that non-preallocated maps are still not safe, since there is
no rcu_read_lock yet in sleepable programs and dynamically allocated
map elements are relying on rcu protection. The sleepable programs
have rcu_read_lock_trace instead. That limitation will be addresses
in the future.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/hashtab.c  | 4 ++--
 kernel/bpf/verifier.c | 7 ++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c1ac7f964bc9..d63912e73ad9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1148,7 +1148,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 		/* unknown flags */
 		return -EINVAL;
 
-	WARN_ON_ONCE(!rcu_read_lock_held());
+	WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());
 
 	key_size = map->key_size;
 
@@ -1202,7 +1202,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
 		/* unknown flags */
 		return -EINVAL;
 
-	WARN_ON_ONCE(!rcu_read_lock_held());
+	WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());
 
 	key_size = map->key_size;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4189edb41b73..9561f2af7710 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10020,9 +10020,14 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		case BPF_MAP_TYPE_HASH:
 		case BPF_MAP_TYPE_LRU_HASH:
 		case BPF_MAP_TYPE_ARRAY:
+		case BPF_MAP_TYPE_PERCPU_HASH:
+		case BPF_MAP_TYPE_PERCPU_ARRAY:
+		case BPF_MAP_TYPE_LRU_PERCPU_HASH:
+		case BPF_MAP_TYPE_ARRAY_OF_MAPS:
+		case BPF_MAP_TYPE_HASH_OF_MAPS:
 			if (!is_preallocated_map(map)) {
 				verbose(env,
-					"Sleepable programs can only use preallocated hash maps\n");
+					"Sleepable programs can only use preallocated maps\n");
 				return -EINVAL;
 			}
 			break;
-- 
2.24.1