linux-kernel - Re: [PATCH] regmap: Use mas_walk() instead of mas

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Message-ID: <20230403201003.5eqmsq7k7igkhzhx@revolver>
Date:   Mon, 3 Apr 2023 16:10:03 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regmap: Use mas_walk() instead of mas_find()

* Mark Brown <broonie@...nel.org> [230403 16:00]:
> Liam recommends using mas_walk() instead of mas_find() for our use case so
> let's do that, it avoids some minor overhead associated with being able to
> restart the operation which we don't need since we do a simple search.
> 
> Suggested-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  drivers/base/regmap/regcache-maple.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/regmap/regcache-maple.c b/drivers/base/regmap/regcache-maple.c
> index 497cc708d277..5d1bc3691830 100644
> --- a/drivers/base/regmap/regcache-maple.c
> +++ b/drivers/base/regmap/regcache-maple.c
> @@ -22,7 +22,9 @@ static int regcache_maple_read(struct regmap *map,
>  
>  	rcu_read_lock();
>  
> -	entry = mas_find(&mas, reg);
> +	mas.index = reg;
> +	mas.last = reg;

You don't need to set mas.index/mas.last here.  You have done so with
MA_STATE(mas, mt, reg, reg); above with the last two arguments.

> +	entry = mas_walk(&mas);
>  	if (!entry) {
>  		rcu_read_unlock();
>  		return -ENOENT;
> @@ -47,7 +49,9 @@ static int regcache_maple_write(struct regmap *map, unsigned int reg,
>  
>  	rcu_read_lock();
>  
> -	entry = mas_find(&mas, reg);
> +	mas.index = reg;
> +	mas.last = reg;

Same here.

> +	entry = mas_walk(&mas);
>  	if (entry) {
>  		entry[reg - mas.index] = val;
>  		rcu_read_unlock();
> 
> ---
> base-commit: f033c26de5a5734625d2dd1dc196745fae186f1b
> change-id: 20230403-regmap-maple-walk-fine-982bbd2dcfe5
> 
> Best regards,
> -- 
> Mark Brown <broonie@...nel.org>
>