Re: [PATCH v2 02/12] bcache: explicitly make cache_set only have single cache

[Hannes Reinecke <hare@xxxxxxx>]

On 8/22/20 1:45 PM, Coly Li wrote:
> Currently although the bcache code has a framework for multiple caches
> in a cache set, but indeed the multiple caches never completed and users
> use md raid1 for multiple copies of the cached data.
>
> This patch does the following change in struct cache_set, to explicitly
> make a cache_set only have single cache,
> - Change pointer array "*cache[MAX_CACHES_PER_SET]" to a single pointer
>    "*cache".
> - Remove pointer array "*cache_by_alloc[MAX_CACHES_PER_SET]".
> - Remove "caches_loaded".
>
> Now the code looks as exactly what it does in practic: only one cache is
> used in the cache set.
>
> Signed-off-by: Coly Li <colyli@xxxxxxx>
> ---
>   drivers/md/bcache/alloc.c  |  2 +-
>   drivers/md/bcache/bcache.h |  8 +++-----
>   drivers/md/bcache/super.c  | 19 ++++++++-----------
>   3 files changed, 12 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
> index 4493ff57476d..3385f6add6df 100644
> --- a/drivers/md/bcache/alloc.c
> +++ b/drivers/md/bcache/alloc.c
> @@ -501,7 +501,7 @@ int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
>   
>   	bkey_init(k);
>   
> -	ca = c->cache_by_alloc[0];
> +	ca = c->cache;
>   	b = bch_bucket_alloc(ca, reserve, wait);
>   	if (b == -1)
>   		goto err;
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index 5ff6e9573935..aa112c1adba1 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -519,9 +519,7 @@ struct cache_set {
>   
>   	struct cache_sb		sb;
>   
> -	struct cache		*cache[MAX_CACHES_PER_SET];
> -	struct cache		*cache_by_alloc[MAX_CACHES_PER_SET];
> -	int			caches_loaded;
> +	struct cache		*cache;
>   
>   	struct bcache_device	**devices;
>   	unsigned int		devices_max_used;
> @@ -808,7 +806,7 @@ static inline struct cache *PTR_CACHE(struct cache_set *c,
>   				      const struct bkey *k,
>   				      unsigned int ptr)
>   {
> -	return c->cache[PTR_DEV(k, ptr)];
> +	return c->cache;
>   }
>   
>   static inline size_t PTR_BUCKET_NR(struct cache_set *c,
> @@ -890,7 +888,7 @@ do {									\
>   /* Looping macros */
>   
>   #define for_each_cache(ca, cs, iter)					\
> -	for (iter = 0; ca = cs->cache[iter], iter < (cs)->sb.nr_in_set; iter++)
> +	for (iter = 0; ca = cs->cache, iter < 1; iter++)
>   
>   #define for_each_bucket(b, ca)						\
>   	for (b = (ca)->buckets + (ca)->sb.first_bucket;			\
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 7057ec48f3d1..e9ccfa17beb8 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1675,7 +1675,7 @@ static void cache_set_free(struct closure *cl)
>   	for_each_cache(ca, c, i)
>   		if (ca) {
>   			ca->set = NULL;
> -			c->cache[ca->sb.nr_this_dev] = NULL;
> +			c->cache = NULL;
>   			kobject_put(&ca->kobj);
>   		}
>   
Please kill 'for_each_cache()', too, and replace it by an if clause.

Cheers,

Hannes
--
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@xxxxxxx                               +49 911 74053 688
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