linux-kernel - Re: [PATCH] loop: avoid out-of-range warning

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Date:   Mon, 27 Sep 2021 11:51:17 +0200
From:   Martijn Coenen <maco@...roid.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Dan Schatzberg <schatzberg.dan@...il.com>,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, llvm@...ts.linux.dev
Subject: Re: [PATCH] loop: avoid out-of-range warning

Thanks!

On Mon, Sep 27, 2021 at 11:43 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> clang warns that the sanity check for page size always succeeds
> when building with 64KB pages:
>
> drivers/block/loop.c:282:27: error: result of comparison of constant 65536 with expression of type 'unsigned short' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>         if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
>                            ~~~~~ ^ ~~~~~~~~~
>
> There is nothing wrong here, so just shut up the check by changing
> the type of the bsize argument.
>
> Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Martijkn Coenen <maco@...roid.com>

> ---
>  drivers/block/loop.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 7bf4686af774..51315a93b399 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -277,7 +277,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>   * @bsize: size to validate
>   */
>  static int
> -loop_validate_block_size(unsigned short bsize)
> +loop_validate_block_size(unsigned int bsize)
>  {
>         if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
>                 return -EINVAL;
> --
> 2.29.2
>