linux-kernel - Re: [PATCH] maple_tree: simplify mas_wr_node

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Message-ID: <20240823081618.GA23044@systemsresearch.io>
Date: Fri, 23 Aug 2024 08:16:18 +0000
From: Hao Li <haoli.tcs@...il.com>
To: Liam.Howlett@...cle.com
Cc: akpm@...ux-foundation.org, maple-tree@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] maple_tree: simplify mas_wr_node_walk for improved
 readability

Sorry, this patch misses a line. v2 has been sent.

On Fri, Aug 23, 2024 at 07:37:19AM +0000, Hao Li wrote:
> Refactor mas_wr_node_walk to make the code more clear and easier to
> understand. The main changes are:
> 
> 1. Replace the forward-iterating loop with a backward-iterating loop.
>    This simplifies the logic for determining the correct range
>    containing mas->index.
> 
> 2. Eliminate the ternary operator.
> 
> The new implementation maintains the same functionality as before, but
> with improved readability. The performance characteristics remain
> essentially the same, as we cannot predict which interval mas->index
> will fall into.
> 
> Signed-off-by: Hao Li <haoli.tcs@...il.com>
> ---
>  lib/maple_tree.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index fe1b01b29..a180f54f5 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -2213,16 +2213,14 @@ static inline void mas_wr_node_walk(struct ma_wr_state *wr_mas)
>  
>  	wr_mas->node = mas_mn(wr_mas->mas);
>  	wr_mas->pivots = ma_pivots(wr_mas->node, wr_mas->type);
> -	count = mas->end = ma_data_end(wr_mas->node, wr_mas->type,
> +	mas->end = ma_data_end(wr_mas->node, wr_mas->type,
>  				       wr_mas->pivots, mas->max);
> -	offset = mas->offset;
> -
> -	while (offset < count && mas->index > wr_mas->pivots[offset])
> -		offset++;
> -
> -	wr_mas->r_max = offset < count ? wr_mas->pivots[offset] : mas->max;
> -	wr_mas->r_min = mas_safe_min(mas, wr_mas->pivots, offset);
> -	wr_mas->offset_end = mas->offset = offset;
> +	wr_mas->r_max = mas->max;
> +	idx = mas->end - 1;
> +	while (idx >= mas->offset && wr_mas->pivots[idx] >= mas->index)
> +		wr_mas->r_max = wr_mas->pivots[idx--];
> +	wr_mas->offset_end = mas->offset = idx + 1;
> +	wr_mas->r_min = mas_safe_min(mas, wr_mas->pivots, mas->offset);
>  }
>  
>  /*
> -- 
> 2.21.0
>