[PATCH 6.1 15/16] bpf: Remove unnecessary check when updating LPM trie

[Alexey Nepomnyashih]

From: Hou Tao <houtao1@xxxxxxxxxx>

commit 156c977c539e87e173f505b23989d7b0ec0bc7d8 upstream.

When "node->prefixlen == matchlen" is true, it means that the node is
fully matched. If "node->prefixlen == key->prefixlen" is false, it means
the prefix length of key is greater than the prefix length of node,
otherwise, matchlen will not be equal with node->prefixlen. However, it
also implies that the prefix length of node must be less than
max_prefixlen.

Therefore, "node->prefixlen == trie->max_prefixlen" will always be false
when the check of "node->prefixlen == key->prefixlen" returns false.
Remove this unnecessary comparison.

Reviewed-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241206110622.1161752-2-houtao@xxxxxxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Alexey Nepomnyashih <sdl@xxxxxxxx>
---
 kernel/bpf/lpm_trie.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index fd6e31e72290..6c96241f49a4 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -358,8 +358,7 @@ static int trie_update_elem(struct bpf_map *map,
 		matchlen = longest_prefix_match(trie, node, key);
 
 		if (node->prefixlen != matchlen ||
-		    node->prefixlen == key->prefixlen ||
-		    node->prefixlen == trie->max_prefixlen)
+		    node->prefixlen == key->prefixlen)
 			break;
 
 		next_bit = extract_bit(key->data, node->prefixlen);
-- 
2.43.0