linux-kernel - Re: [PATCH 1/9] dm integrity: fix out-of-range warning

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Message-ID: <CAFhGd8ortE-ahJD+BDss7qbW-=Hn2_L_r2OZfa0V87mG2KV3+g@mail.gmail.com>
Date: Thu, 28 Mar 2024 14:58:08 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: linux-kernel@...r.kernel.org, Alasdair Kergon <agk@...hat.com>, 
	Mike Snitzer <snitzer@...nel.org>, Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...ts.linux.dev, 
	Nathan Chancellor <nathan@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Eric Biggers <ebiggers@...gle.com>, llvm@...ts.linux.dev
Subject: Re: [PATCH 1/9] dm integrity: fix out-of-range warning

On Thu, Mar 28, 2024 at 7:31 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> Depending on the value of CONFIG_HZ, clang compares about a pointless
> comparison:
>
> drivers/md/dm-integrity.c:4085:12: error: result of comparison of constant 42949672950 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>                         if (val >= (uint64_t)UINT_MAX * 1000 / HZ) {
>
> As the check remains useful for other configurations, shut up the
> warning by adding a second type cast to uint64_t.

Yeah, nice.

>
> Fixes: 468dfca38b1a ("dm integrity: add a bitmap mode")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Justin Stitt <justinstitt@...gle.com>

> ---
>  drivers/md/dm-integrity.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
> index 37b9f8f1ae1a..7f3dc8ee6ab8 100644
> --- a/drivers/md/dm-integrity.c
> +++ b/drivers/md/dm-integrity.c
> @@ -4221,7 +4221,7 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned int argc, char **argv
>                 } else if (sscanf(opt_string, "sectors_per_bit:%llu%c", &llval, &dummy) == 1) {
>                         log2_sectors_per_bitmap_bit = !llval ? 0 : __ilog2_u64(llval);
>                 } else if (sscanf(opt_string, "bitmap_flush_interval:%u%c", &val, &dummy) == 1) {
> -                       if (val >= (uint64_t)UINT_MAX * 1000 / HZ) {
> +                       if ((uint64_t)val >= (uint64_t)UINT_MAX * 1000 / HZ) {
>                                 r = -EINVAL;
>                                 ti->error = "Invalid bitmap_flush_interval argument";
>                                 goto bad;
> --
> 2.39.2
>