bcache: explicitly make cache_set only have single cache

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@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 4493ff5..3385f6a 100644 (file)
--- 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 5ff6e95..aa112c1 100644 (file)
--- 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 b4176b8..739cf29 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1674,7 +1674,7 @@ 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);
                }
 
@@ -2165,7 +2165,7 @@ static const char *register_cache_set(struct cache *ca)
 
        list_for_each_entry(c, &bch_cache_sets, list)
                if (!memcmp(c->sb.set_uuid, ca->sb.set_uuid, 16)) {
-                       if (c->cache[ca->sb.nr_this_dev])
+                       if (c->cache)
                                return "duplicate cache set member";
 
                        if (!can_attach_cache(ca, c))
@@ -2215,14 +2215,11 @@ found:
 
        kobject_get(&ca->kobj);
        ca->set = c;
-       ca->set->cache[ca->sb.nr_this_dev] = ca;
-       c->cache_by_alloc[c->caches_loaded++] = ca;
+       ca->set->cache = ca;
 
-       if (c->caches_loaded == c->sb.nr_in_set) {
-               err = "failed to run cache set";
-               if (run_cache_set(c) < 0)
-                       goto err;
-       }
+       err = "failed to run cache set";
+       if (run_cache_set(c) < 0)
+               goto err;
 
        return NULL;
 err:
@@ -2239,8 +2236,8 @@ void bch_cache_release(struct kobject *kobj)
        unsigned int i;
 
        if (ca->set) {
-               BUG_ON(ca->set->cache[ca->sb.nr_this_dev] != ca);
-               ca->set->cache[ca->sb.nr_this_dev] = NULL;
+               BUG_ON(ca->set->cache != ca);
+               ca->set->cache = NULL;
        }
 
        free_pages((unsigned long) ca->disk_buckets, ilog2(meta_bucket_pages(&ca->sb)));