bcache: move closure debug file into debug directory

In current code closure debug file is outside of debug directory
and when unloading module there is lack of removing operation
for closure debug file, so it will cause creating error when trying
to reload  module.

This patch move closure debug file into "bcache" debug direcory
so that the file can get deleted properly.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Tang Junhui <tang.junhui@zte.com.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index af89408..028f7b3 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c
@@ -17,7 +17,7 @@
 #include <linux/random.h>
 #include <linux/seq_file.h>
 
-static struct dentry *debug;
+struct dentry *bcache_debug;
 
 #ifdef CONFIG_BCACHE_DEBUG
 
@@ -232,11 +232,11 @@ static const struct file_operations cache_set_debug_ops = {
 
 void bch_debug_init_cache_set(struct cache_set *c)
 {
-	if (!IS_ERR_OR_NULL(debug)) {
+	if (!IS_ERR_OR_NULL(bcache_debug)) {
 		char name[50];
 		snprintf(name, 50, "bcache-%pU", c->sb.set_uuid);
 
-		c->debug = debugfs_create_file(name, 0400, debug, c,
+		c->debug = debugfs_create_file(name, 0400, bcache_debug, c,
 					       &cache_set_debug_ops);
 	}
 }
@@ -245,13 +245,13 @@ void bch_debug_init_cache_set(struct cache_set *c)
 
 void bch_debug_exit(void)
 {
-	if (!IS_ERR_OR_NULL(debug))
-		debugfs_remove_recursive(debug);
+	if (!IS_ERR_OR_NULL(bcache_debug))
+		debugfs_remove_recursive(bcache_debug);
 }
 
 int __init bch_debug_init(struct kobject *kobj)
 {
-	debug = debugfs_create_dir("bcache", NULL);
+	bcache_debug = debugfs_create_dir("bcache", NULL);
 
-	return IS_ERR_OR_NULL(debug);
+	return IS_ERR_OR_NULL(bcache_debug);
 }