Re: [PATCH bpf-next v2] bpf: remove set but not used variable 'dst_known'

[Song Liu]

> On Apr 17, 2020, at 6:37 PM, Mao Wenan <maowenan@xxxxxxxxxx> wrote:
> 
> Fixes gcc '-Wunused-but-set-variable' warning:
> 
> kernel/bpf/verifier.c:5603:18: warning: variable âdst_knownâ
> set but not used [-Wunused-but-set-variable], delete this
> variable.
> 
> Signed-off-by: Mao Wenan <maowenan@xxxxxxxxxx>

Acked-by: Song Liu <songliubraving@xxxxxx>

With one nit below. 

> ---
> v2: remove fixes tag in commit log. 
> kernel/bpf/verifier.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 04c6630cc18f..c9f50969a689 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5600,7 +5600,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
> {
> 	struct bpf_reg_state *regs = cur_regs(env);
> 	u8 opcode = BPF_OP(insn->code);
> -	bool src_known, dst_known;
> +	bool src_known;

This is not a hard rule, but we prefer to keep variable definition in 
"reverse Christmas tree" order. Since we are on this function, let's 
reorder these definitions to something like:

        u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
        struct bpf_reg_state *regs = cur_regs(env);
        u8 opcode = BPF_OP(insn->code);
        u32 dst = insn->dst_reg;
        s64 smin_val, smax_val;
        u64 umin_val, umax_val;
        bool src_known;
        int ret;