linux-kernel - Re: [PATCH] bpf: Convert to use the preferred fallthrough macro

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Date:   Fri, 14 Aug 2020 09:55:11 -0700
From:   Yonghong Song <yhs@...com>
To:     Miaohe Lin <linmiaohe@...wei.com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <kafai@...com>, <songliubraving@...com>,
        <andriin@...com>, <john.fastabend@...il.com>,
        <kpsingh@...omium.org>, <davem@...emloft.net>, <kuba@...nel.org>,
        <hawk@...nel.org>
CC:     <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: Convert to use the preferred fallthrough macro



On 8/14/20 2:16 AM, Miaohe Lin wrote:
> Convert the uses of fallthrough comments to fallthrough macro.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

This is not a bug fix but rather an enhancement so not sure whether
this should push to bpf tree or wait until bpf-next.

It may be worthwhile to mention Commit 294f69e662d1 
("compiler_attributes.h: Add 'fallthrough' pseudo keyword for 
switch/case use") so people can understand why this patch is
needed.

With above suggestions,
Acked-by: Yonghong Song <yhs@...com>

> ---
>   kernel/bpf/cgroup.c   | 2 +-
>   kernel/bpf/cpumap.c   | 2 +-
>   kernel/bpf/syscall.c  | 2 +-
>   kernel/bpf/verifier.c | 6 +++---
>   4 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 83ff127ef7ae..e21de4f1754c 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -1794,7 +1794,7 @@ static bool cg_sockopt_is_valid_access(int off, int size,
>   			return prog->expected_attach_type ==
>   				BPF_CGROUP_GETSOCKOPT;
>   		case offsetof(struct bpf_sockopt, optname):
> -			/* fallthrough */
> +			fallthrough;
>   		case offsetof(struct bpf_sockopt, level):
>   			if (size != size_default)
>   				return false;
> diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
> index f1c46529929b..6386b7bb98f2 100644
> --- a/kernel/bpf/cpumap.c
> +++ b/kernel/bpf/cpumap.c
> @@ -279,7 +279,7 @@ static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
>   			break;
>   		default:
>   			bpf_warn_invalid_xdp_action(act);
> -			/* fallthrough */
> +			fallthrough;
>   		case XDP_DROP:
>   			xdp_return_frame(xdpf);
>   			stats->drop++;
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 86299a292214..1bf960aa615c 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2029,7 +2029,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
>   	case BPF_PROG_TYPE_EXT:
>   		if (expected_attach_type)
>   			return -EINVAL;
> -		/* fallthrough */
> +		fallthrough;
>   	default:
>   		return 0;
>   	}
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index ef938f17b944..1e7f34663f86 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2639,7 +2639,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
>   	case BPF_PROG_TYPE_CGROUP_SKB:
>   		if (t == BPF_WRITE)
>   			return false;
> -		/* fallthrough */
> +		fallthrough;
>   
>   	/* Program types with direct read + write access go here! */
>   	case BPF_PROG_TYPE_SCHED_CLS:
> @@ -5236,7 +5236,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
>   				off_reg == dst_reg ? dst : src);
>   			return -EACCES;
>   		}
> -		/* fall-through */
> +		fallthrough;
>   	default:
>   		break;
>   	}
> @@ -10988,7 +10988,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
>   	default:
>   		if (!prog_extension)
>   			return -EINVAL;
> -		/* fallthrough */
> +		fallthrough;
>   	case BPF_MODIFY_RETURN:
>   	case BPF_LSM_MAC:
>   	case BPF_TRACE_FENTRY:
>