bcache: add reclaimed_journal_buckets to struct cache_set

Now we have counters for how many times jouranl is reclaimed, how many
times cached dirty btree nodes are flushed, but we don't know how many
jouranl buckets are really reclaimed.

This patch adds reclaimed_journal_buckets into struct cache_set, this
is an increasing only counter, to tell how many journal buckets are
reclaimed since cache set runs. From all these three counters (reclaim,
reclaimed_journal_buckets, flush_write), we can have idea how well
current journal space reclaim code works.

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

drivers/md/bcache/bcache.h

@@ -705,6 +705,7 @@ struct cache_set {
 	atomic_long_t		writeback_keys_failed;
 
 	atomic_long_t		reclaim;
+	atomic_long_t		reclaimed_journal_buckets;
 	atomic_long_t		flush_write;
 
 	enum			{

drivers/md/bcache/journal.c

@@ -614,6 +614,7 @@ static void journal_reclaim(struct cache_set *c)
 		k->ptr[n++] = MAKE_PTR(0,
 				  bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
 				  ca->sb.nr_this_dev);
+		atomic_long_inc(&c->reclaimed_journal_buckets);
 	}
 
 	if (n) {

drivers/md/bcache/sysfs.c

@@ -82,6 +82,7 @@ read_attribute(bset_tree_stats);
 read_attribute(state);
 read_attribute(cache_read_races);
 read_attribute(reclaim);
+read_attribute(reclaimed_journal_buckets);
 read_attribute(flush_write);
 read_attribute(writeback_keys_done);
 read_attribute(writeback_keys_failed);
@@ -705,6 +706,9 @@ SHOW(__bch_cache_set)
 	sysfs_print(reclaim,
 		    atomic_long_read(&c->reclaim));
 
+	sysfs_print(reclaimed_journal_buckets,
+		    atomic_long_read(&c->reclaimed_journal_buckets));
+
 	sysfs_print(flush_write,
 		    atomic_long_read(&c->flush_write));
 
@@ -931,6 +935,7 @@ static struct attribute *bch_cache_set_internal_files[] = {
 	&sysfs_bset_tree_stats,
 	&sysfs_cache_read_races,
 	&sysfs_reclaim,
+	&sysfs_reclaimed_journal_buckets,
 	&sysfs_flush_write,
 	&sysfs_writeback_keys_done,
 	&sysfs_writeback_keys_failed,