linux-kernel - Re: [PATCH] block: use int type to store negative value

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Message-ID: <b6c44c7c-282f-4f1c-aeb4-af0b39bfae78@oracle.com>
Date: Tue, 2 Sep 2025 17:11:02 +0100
From: John Garry <john.g.garry@...cle.com>
To: Qianfeng Rong <rongqianfeng@...o.com>, Jens Axboe <axboe@...nel.dk>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: use int type to store negative value

On 02/09/2025 14:09, Qianfeng Rong wrote:

maybe be more exact in the subject, like "block: use int to store 
blk_stack_limits() return value"

> Change the 'ret' variable in blk_stack_limits() from unsigned int to int,
> as it needs to store negative value -1.
> 
> Storing the negative error codes in unsigned type, or performing equality
> comparisons (e.g., ret == -1), doesn't cause an issue at runtime [1] but
> can be confusing.  Additionally, assigning negative error codes to unsigned
> type may trigger a GCC warning when the -Wsign-conversion flag is enabled.
> 
> No effect on runtime.
> 
> Link: https://urldefense.com/v3/__https://lore.kernel.org/all/x3wogjf6vgpkisdhg3abzrx7v7zktmdnfmqeih5kosszmagqfs@oh3qxrgzkikf/__;!!ACWV5N9M2RV99hQ!JfWLPo_X7bYZL3xujNcmSob_sFzfvnOmFwzTQ-buSgEyxB4Rx04CZsZmcwf8CSAME6ySlTkSsgsc2EWpNVX-LC_C$  #1
> Signed-off-by: Qianfeng Rong <rongqianfeng@...o.com>

Reviewed-by: John Garry <john.g.garry@...cle.com>

> ---
>   block/blk-settings.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index d6438e6c276d..693bc8d20acf 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -763,7 +763,8 @@ static void blk_stack_atomic_writes_limits(struct queue_limits *t,
>   int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
>   		     sector_t start)
>   {
> -	unsigned int top, bottom, alignment, ret = 0;
> +	unsigned int top, bottom, alignment;
> +	int ret = 0;
>   
>   	t->features |= (b->features & BLK_FEAT_INHERIT_MASK);
>