linux-kernel - Re: [PATCH 2/2] bcache: Convert to lock_cmp

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Message-ID: <20230510130151.GL4253@hirez.programming.kicks-ass.net>
Date:   Wed, 10 May 2023 15:01:51 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     linux-kernel@...r.kernel.org, Coly Li <colyli@...e.de>
Subject: Re: [PATCH 2/2] bcache: Convert to lock_cmp_fn

On Tue, May 09, 2023 at 03:58:47PM -0400, Kent Overstreet wrote:
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: Coly Li <colyli@...e.de>
> ---
>  drivers/md/bcache/btree.c | 23 ++++++++++++++++++++++-
>  drivers/md/bcache/btree.h |  4 ++--
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index 147c493a98..569f48958b 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -559,6 +559,27 @@ static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
>  	}
>  }
>  
> +#define cmp_int(l, r)		((l > r) - (l < r))
> +
> +#ifdef CONFIG_PROVE_LOCKING
> +static int btree_lock_cmp_fn(const struct lockdep_map *_a,
> +			     const struct lockdep_map *_b)
> +{
> +	const struct btree *a = container_of(_a, struct btree, lock.dep_map);
> +	const struct btree *b = container_of(_b, struct btree, lock.dep_map);
> +
> +	return -cmp_int(a->level, b->level) ?: bkey_cmp(&a->key, &b->key);
> +}
> +
> +static void btree_lock_print_fn(const struct lockdep_map *map)
> +{
> +	const struct btree *b = container_of(map, struct btree, lock.dep_map);
> +
> +	printk(KERN_CONT " l=%u %llu:%llu", b->level,
> +	       KEY_INODE(&b->key), KEY_OFFSET(&b->key));
> +}
> +#endif
> +
>  static struct btree *mca_bucket_alloc(struct cache_set *c,
>  				      struct bkey *k, gfp_t gfp)
>  {
> @@ -572,7 +593,7 @@ static struct btree *mca_bucket_alloc(struct cache_set *c,
>  		return NULL;
>  
>  	init_rwsem(&b->lock);
> -	lockdep_set_novalidate_class(&b->lock);
> +	lock_set_cmp_fn(&b->lock, btree_lock_cmp_fn, btree_lock_print_fn);
>  	mutex_init(&b->write_lock);
>  	lockdep_set_novalidate_class(&b->write_lock);

I can't help but notice you've got yet another novalidate_class usage
here. What does it take to get rid of that?