[PATCH bpf v3 1/9] bpf: Remove unnecessary check when updating LPM trie

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From: Hou Tao <houtao1@xxxxxxxxxx>

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>
---
 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 9b60eda0f727..73fd593d3745 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -364,8 +364,7 @@ static long 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);
-- 
2.29.2





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