netdev - [PATCH bpf-next 2/7] bpf: Bail out early in __htab_map_lookup_and_delete

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Message-Id: <20250107085559.3081563-3-houtao@huaweicloud.com>
Date: Tue,  7 Jan 2025 16:55:54 +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>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	houtao1@...wei.com,
	xukuohai@...wei.com
Subject: [PATCH bpf-next 2/7] bpf: Bail out early in __htab_map_lookup_and_delete_elem()

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

Use goto statement to bail out early when the target element is not
found, instead of using a large else branch to handle the more likely
case. This change doesn't affect functionality and simply make the code
cleaner.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 kernel/bpf/hashtab.c | 51 ++++++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 8fecf21c132a..59eb117908c5 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1641,37 +1641,38 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
 	l = lookup_elem_raw(head, hash, key, key_size);
 	if (!l) {
 		ret = -ENOENT;
-	} else {
-		if (is_percpu) {
-			u32 roundup_value_size = round_up(map->value_size, 8);
-			void __percpu *pptr;
-			int off = 0, cpu;
+		goto out_unlock;
+	}
 
-			pptr = htab_elem_get_ptr(l, key_size);
-			for_each_possible_cpu(cpu) {
-				copy_map_value_long(&htab->map, value + off, per_cpu_ptr(pptr, cpu));
-				check_and_init_map_value(&htab->map, value + off);
-				off += roundup_value_size;
-			}
-		} else {
-			u32 roundup_key_size = round_up(map->key_size, 8);
+	if (is_percpu) {
+		u32 roundup_value_size = round_up(map->value_size, 8);
+		void __percpu *pptr;
+		int off = 0, cpu;
 
-			if (flags & BPF_F_LOCK)
-				copy_map_value_locked(map, value, l->key +
-						      roundup_key_size,
-						      true);
-			else
-				copy_map_value(map, value, l->key +
-					       roundup_key_size);
-			/* Zeroing special fields in the temp buffer */
-			check_and_init_map_value(map, value);
+		pptr = htab_elem_get_ptr(l, key_size);
+		for_each_possible_cpu(cpu) {
+			copy_map_value_long(&htab->map, value + off, per_cpu_ptr(pptr, cpu));
+			check_and_init_map_value(&htab->map, value + off);
+			off += roundup_value_size;
 		}
+	} else {
+		u32 roundup_key_size = round_up(map->key_size, 8);
 
-		hlist_nulls_del_rcu(&l->hash_node);
-		if (!is_lru_map)
-			free_htab_elem(htab, l);
+		if (flags & BPF_F_LOCK)
+			copy_map_value_locked(map, value, l->key +
+					      roundup_key_size,
+					      true);
+		else
+			copy_map_value(map, value, l->key +
+				       roundup_key_size);
+		/* Zeroing special fields in the temp buffer */
+		check_and_init_map_value(map, value);
 	}
+	hlist_nulls_del_rcu(&l->hash_node);
+	if (!is_lru_map)
+		free_htab_elem(htab, l);
 
+out_unlock:
 	htab_unlock_bucket(htab, b, hash, bflags);
 
 	if (is_lru_map && l)
-- 
2.29.2