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

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On 8/15/20 6:10 AM, 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;

Maybe drop variable 'ca' altogether?

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;			\

I guess 'for_each_cache' can be killed, too.

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)));

Cheers,

Hannes
--
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@xxxxxxx                               +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer



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