linux-kernel - Re: [PATCH] block/merge: remove unnecessary min() with UINT

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Message-ID: <20250215115144.6a10dad8@pumpkin>
Date: Sat, 15 Feb 2025 11:51:44 +0000
From: David Laight <david.laight.linux@...il.com>
To: Caleb Sander Mateos <csander@...estorage.com>
Cc: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block/merge: remove unnecessary min() with UINT_MAX

On Fri, 14 Feb 2025 12:36:36 -0700
Caleb Sander Mateos <csander@...estorage.com> wrote:

> In bvec_split_segs(), max_bytes is an unsigned, so it must be less than
> or equal to UINT_MAX. Remove the unnecessary min().
> 
> Prior to commit 67927d220150 ("block/merge: count bytes instead of
> sectors"), the min() was with UINT_MAX >> 9, so it did have an effect.
> 
> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
> ---
>  block/blk-merge.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 15cd231d560c..39b738c0e4c9 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -268,11 +268,11 @@ static inline unsigned get_max_segment_size(const struct queue_limits *lim,
>   */
>  static bool bvec_split_segs(const struct queue_limits *lim,
>  		const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes,
>  		unsigned max_segs, unsigned max_bytes)
>  {
> -	unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
> +	unsigned max_len = max_bytes - *bytes;

More interestingly, what stops *bytes being larger than max_bytes?

	David

>  	unsigned len = min(bv->bv_len, max_len);
>  	unsigned total_len = 0;
>  	unsigned seg_size = 0;
>  
>  	while (len && *nsegs < max_segs) {