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 <redacted>
---
  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);
  		}