linux-kernel - Re: [PATCH v3] nfs: remove incorrect fallthrough label

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Date:   Thu, 24 Sep 2020 10:19:08 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>
Cc:     "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        Joe Perches <joe@...ches.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Hongxiang Lou <louhongxiang@...wei.com>,
        linux-nfs@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v3] nfs: remove incorrect fallthrough label

Hello maintainers,
Would you mind please picking up this patch?  KernelCI has been
erroring for over a week without it.

On Thu, Sep 17, 2020 at 2:45 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> There is no case after the default from which to fallthrough to. Clang
> will error in this case (unhelpfully without context, see link below)
> and GCC will with -Wswitch-unreachable.
>
> The previous commit should have just replaced the comment with a break
> statement.
>
> If we consider implicit fallthrough to be a design mistake of C, then
> all case statements should be terminated with one of the following
> statements:
> * break
> * continue
> * return
> * fallthrough
> * goto
> * (call of function with __attribute__(__noreturn__))
>
> Fixes: 2a1390c95a69 ("nfs: Convert to use the preferred fallthrough macro")
> Link: https://bugs.llvm.org/show_bug.cgi?id=47539
> Acked-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>
> Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
> Suggested-by: Joe Perches <joe@...ches.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> Changes v3:
> * update the commit message as per Joe.
> * collect tags.
>
> Changes v2:
> * add break rather than no terminating statement as per Joe.
> * add Joe's suggested by tag.
> * add blurb about acceptable terminal statements.
>
>  fs/nfs/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index d20326ee0475..eb2401079b04 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -889,7 +889,7 @@ static struct nfs_server *nfs_try_mount_request(struct fs_context *fc)
>                 default:
>                         if (rpcauth_get_gssinfo(flavor, &info) != 0)
>                                 continue;
> -                       fallthrough;
> +                       break;
>                 }
>                 dfprintk(MOUNT, "NFS: attempting to use auth flavor %u\n", flavor);
>                 ctx->selected_flavor = flavor;
> --
> 2.28.0.681.g6f77f65b4e-goog
>


-- 
Thanks,
~Nick Desaulniers