[PATCH bpf-next v2 08/22] bpf: Remove dead code through the patch list

[Qiliang Yuan]

bpf_opt_remove_dead_code() removes every range of instructions that the
verifier never reached with verifier_remove_insns().

Each removal moves the tail of the program and of its aux data and
walks all of it, so a program with many unreached ranges pays
O(prog->len) for each of them.

Queue the removal of each unreached instruction with
bpf_patch_list_del() and commit them once.

Signed-off-by: Qiliang Yuan <odys.yuan@xxxxxxxxx>
---
 kernel/bpf/fixups.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c
index 1a1a374a076b1..95f4fe5d607e6 100644
--- a/kernel/bpf/fixups.c
+++ b/kernel/bpf/fixups.c
@@ -1018,21 +1018,14 @@ int bpf_opt_remove_dead_code(struct bpf_verifier_env *env)
 	keep_funcs_with_addr_taken(env);
 
 	for (i = 0; i < insn_cnt; i++) {
-		int j;
-
-		j = 0;
-		while (i + j < insn_cnt && !aux_data[i + j].seen)
-			j++;
-		if (!j)
+		if (aux_data[i].seen)
 			continue;
-
-		err = verifier_remove_insns(env, i, j);
+		err = bpf_patch_list_del(env, i);
 		if (err)
 			return err;
-		insn_cnt = env->prog->len;
 	}
 
-	return 0;
+	return bpf_patch_list_commit(env);
 }
 
 int bpf_opt_remove_nops(struct bpf_verifier_env *env)

-- 
2.43.0