linux-kernel - Re: [PATCH 3/7] bcachefs: Fix -Wformat in bch2_alloc_v4

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Message-ID: <20230913214600.y3eo3emayljnxfuy@google.com>
Date:   Wed, 13 Sep 2023 21:46:00 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     kent.overstreet@...ux.dev, bfoster@...hat.com,
        linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev
Subject: Re: [PATCH 3/7] bcachefs: Fix -Wformat in bch2_alloc_v4_invalid()

On Tue, Sep 12, 2023 at 12:15:40PM -0700, Nathan Chancellor wrote:
> When building bcachefs for 32-bit ARM, there is a compiler warning in
> bch2_alloc_v4_invalid() due to use of an incorrect format specifier:
>
>   fs/bcachefs/alloc_background.c:246:30: error: format specifies type 'unsigned long' but the argument has type 'unsigned int' [-Werror,-Wformat]
>     245 |                 prt_printf(err, "bad val size (%u > %lu)",
>         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         |                                                     %u
>     246 |                        alloc_v4_u64s(a.v), bkey_val_u64s(k.k));
>         |                        ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
>   fs/bcachefs/bkey.h:58:27: note: expanded from macro 'bkey_val_u64s'
>      58 | #define bkey_val_u64s(_k)       ((_k)->u64s - BKEY_U64s)
>         |                                 ^
>   fs/bcachefs/util.h:223:54: note: expanded from macro 'prt_printf'
>     223 | #define prt_printf(_out, ...)           bch2_prt_printf(_out, __VA_ARGS__)
>         |                                                               ^~~~~~~~~~~
>
> This expression is of type 'size_t'. On 64-bit architectures, size_t is
> 'unsigned long', so there is no warning when using %lu but on 32-bit
> architectures, size_t is 'unsigned int'. Use '%zu', the format specifier
> for 'size_t' to eliminate the warning.
>
> Fixes: 11be8e8db283 ("bcachefs: New on disk format: Backpointers")
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Justin Stitt <justinstitt@...gle.com>

> ---
>  fs/bcachefs/alloc_background.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/alloc_background.c b/fs/bcachefs/alloc_background.c
> index 540d94c0cceb..67e73864823c 100644
> --- a/fs/bcachefs/alloc_background.c
> +++ b/fs/bcachefs/alloc_background.c
> @@ -242,7 +242,7 @@ int bch2_alloc_v4_invalid(const struct bch_fs *c, struct bkey_s_c k,
>  	struct bkey_s_c_alloc_v4 a = bkey_s_c_to_alloc_v4(k);
>
>  	if (alloc_v4_u64s(a.v) > bkey_val_u64s(k.k)) {
> -		prt_printf(err, "bad val size (%u > %lu)",
> +		prt_printf(err, "bad val size (%u > %zu)",
>  		       alloc_v4_u64s(a.v), bkey_val_u64s(k.k));
>  		return -BCH_ERR_invalid_bkey;
>  	}
>
> --
> 2.42.0
>