[PATCH] maple_tree: simplify mas_wr_node_walk for improved readability

[PATCH] maple_tree: simplify mas_wr_node_walk for improved readability

[Hao Li]

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@gmail.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

Re: [PATCH] maple_tree: simplify mas_wr_node_walk for improved readability

[Hao Li]

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@gmail.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
>