[PATCH v1 02/14] bcache: explicitly make cache_set only have single cache

colyli
2020-08-15T22:24:01Z

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>
---
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);
}

@@ -2166,7 +2166,7 @@ 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))
@@ -2216,14 +2216,11 @@ static const char *register_cache_set(struct cache *ca)

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:
@@ -2240,8 +2237,8 @@ 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)));
--
2.26.2