linux-kernel - Re: [PATCH 1/5] maple_tree: Allow external locks to be configured with their map

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Message-ID: <ZsePxD2FtYcBIaD5@casper.infradead.org>
Date: Thu, 22 Aug 2024 20:21:40 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Mark Brown <broonie@...nel.org>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
	maple-tree@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] maple_tree: Allow external locks to be configured
 with their map

On Thu, Aug 22, 2024 at 08:13:35PM +0100, Mark Brown wrote:
> Currently the maple tree code allows external locks to be configured by
> passing the lock itself. This is generally helpful and convenient but is

No, it's a really bad idea.  Stop doing it.  Use the internal lock.
It's a temporary hack we put in and I'm really regretting allowing it.

> not ideal for situations like the regmap maple tree cache where we support
> configurable locking at the regmap level and don't have the lock type when
> we are configuring the maple tree. Add a helper that allows us to pass the
> dep map directly to help with these situations. Since such code is already
> peering at the lockdep internals enough to be looking at the map no stub
> is provided.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  include/linux/maple_tree.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
> index a53ad4dabd7e..bdc6b133abdc 100644
> --- a/include/linux/maple_tree.h
> +++ b/include/linux/maple_tree.h
> @@ -193,6 +193,9 @@ typedef struct lockdep_map *lockdep_map_p;
>  #define mt_set_external_lock(mt, lock)					\
>  	(mt)->ma_external_lock = &(lock)->dep_map
>  
> +#define mt_set_external_lock_dep_map(mt, dep_map)			\
> +	(mt)->ma_external_lock = dep_map
> +
>  #define mt_on_stack(mt)			(mt).ma_external_lock = NULL
>  #else
>  typedef struct { /* nothing */ } lockdep_map_p;
> 
> -- 
> 2.39.2
> 
> 
> -- 
> maple-tree mailing list
> maple-tree@...ts.infradead.org
> https://lists.infradead.org/mailman/listinfo/maple-tree

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