linux-kernel - Re: [PATCH] block: t10-pi: fix -Wswitch warning

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Date:   Thu, 19 Sep 2019 09:21:14 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        linux-block@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Nathan Chancellor <natechancellor@...il.com>, kbuild-all@...org
Subject: Re: [PATCH] block: t10-pi: fix -Wswitch warning

On Thu, Sep 19, 2019 at 6:57 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> Changing the switch() statement to symbolic constants made
> the compiler (at least clang-9, did not check gcc) notice that
> there is one enum value that is not handled here:
>
> block/t10-pi.c:62:11: error: enumeration value 'T10_PI_TYPE0_PROTECTION' not handled in switch [-Werror,-Wswitch]
>
> Add another case for the missing value and do nothing there
> based on the assumption that the code was working correctly
> already.
>
> Fixes: 9b2061b1a262 ("block: use symbolic constants for t10_pi type")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reported-by: kbuild test robot <lkp@...el.com>
https://groups.google.com/forum/#!topic/clang-built-linux/awgY7hmSCCM
Hard to say what's the right thing to do here, there's not a lot of
other switches on this variable.  That enum value barely even shows up
in the kernel.  Since this is no functional change:
Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>
Thanks for sending the patch.

> ---
>  block/t10-pi.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/block/t10-pi.c b/block/t10-pi.c
> index 0c0120a672f9..055fac923946 100644
> --- a/block/t10-pi.c
> +++ b/block/t10-pi.c
> @@ -60,6 +60,8 @@ static blk_status_t t10_pi_verify(struct blk_integrity_iter *iter,
>                 __be16 csum;
>
>                 switch (type) {
> +               case T10_PI_TYPE0_PROTECTION:
> +                       break;
>                 case T10_PI_TYPE1_PROTECTION:
>                 case T10_PI_TYPE2_PROTECTION:
>                         if (pi->app_tag == T10_PI_APP_ESCAPE)
> --
-- 
Thanks,
~Nick Desaulniers