netdev - [PATCH bpf-next 02/19] bpf: Remove migrate_{disable|enable} in ->map_for_each

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Message-Id: <20250106081900.1665573-3-houtao@huaweicloud.com>
Date: Mon,  6 Jan 2025 16:18:43 +0800
From: Hou Tao <houtao@...weicloud.com>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Hao Luo <haoluo@...gle.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Daniel Borkmann <daniel@...earbox.net>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	houtao1@...wei.com,
	xukuohai@...wei.com
Subject: [PATCH bpf-next 02/19] bpf: Remove migrate_{disable|enable} in ->map_for_each_callback

From: Hou Tao <houtao1@...wei.com>

BPF program may call bpf_for_each_map_elem(), and it will call
the ->map_for_each_callback callback of related bpf map. Considering the
running context of bpf program has already disabled migration, remove
the unnecessary migrate_{disable|enable} pair in the implementations of
->map_for_each_callback.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 kernel/bpf/arraymap.c |  6 ++----
 kernel/bpf/hashtab.c  | 11 +++++------
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 6cdbb4c33d31..eb28c0f219ee 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -735,13 +735,13 @@ static long bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback
 	u64 ret = 0;
 	void *val;
 
+	cant_migrate();
+
 	if (flags != 0)
 		return -EINVAL;
 
 	is_percpu = map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
 	array = container_of(map, struct bpf_array, map);
-	if (is_percpu)
-		migrate_disable();
 	for (i = 0; i < map->max_entries; i++) {
 		if (is_percpu)
 			val = this_cpu_ptr(array->pptrs[i]);
@@ -756,8 +756,6 @@ static long bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback
 			break;
 	}
 
-	if (is_percpu)
-		migrate_enable();
 	return num_elems;
 }
 
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 3ec941a0ea41..42af7fac61b9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2208,17 +2208,18 @@ static long bpf_for_each_hash_elem(struct bpf_map *map, bpf_callback_t callback_
 	bool is_percpu;
 	u64 ret = 0;
 
+	cant_migrate();
+
 	if (flags != 0)
 		return -EINVAL;
 
 	is_percpu = htab_is_percpu(htab);
 
 	roundup_key_size = round_up(map->key_size, 8);
-	/* disable migration so percpu value prepared here will be the
-	 * same as the one seen by the bpf program with bpf_map_lookup_elem().
+	/* migration has been disabled, so percpu value prepared here will be
+	 * the same as the one seen by the bpf program with
+	 * bpf_map_lookup_elem().
 	 */
-	if (is_percpu)
-		migrate_disable();
 	for (i = 0; i < htab->n_buckets; i++) {
 		b = &htab->buckets[i];
 		rcu_read_lock();
@@ -2244,8 +2245,6 @@ static long bpf_for_each_hash_elem(struct bpf_map *map, bpf_callback_t callback_
 		rcu_read_unlock();
 	}
 out:
-	if (is_percpu)
-		migrate_enable();
 	return num_elems;
 }
 
-- 
2.29.2