bcache: return 0 from bch_debug_init() if CONFIG_DEBUG_FS=n

Commit 539d39e ("bcache: fix wrong return value in bch_debug_init()")
returns the return value of debugfs_create_dir() to bcache_init(). When
CONFIG_DEBUG_FS=n, bch_debug_init() always returns 1 and makes
bcache_init() failedi.

This patch makes bch_debug_init() always returns 0 if CONFIG_DEBUG_FS=n,
so bcache can continue to work for the kernels which don't have debugfs
enanbled.

Changelog:
v4: Add Acked-by from Kent Overstreet.
v3: Use IS_ENABLED(CONFIG_DEBUG_FS) to replace #ifdef DEBUG_FS.
v2: Remove a warning information
v1: Initial version.

Fixes: Commit 539d39e ("bcache: fix wrong return value in bch_debug_init()")
Cc: [email protected]
Signed-off-by: Coly Li <[email protected]>
Reported-by: Massimo B. <[email protected]>
Reported-by: Kai Krakow <[email protected]>
Tested-by: Kai Krakow <[email protected]>
Acked-by: Kent Overstreet <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: Coly Li

drivers/md/bcache/debug.c

@@ -250,7 +250,9 @@ void bch_debug_exit(void)
 
 int __init bch_debug_init(struct kobject *kobj)
 {
-	bcache_debug = debugfs_create_dir("bcache", NULL);
+	if (!IS_ENABLED(CONFIG_DEBUG_FS))
+		return 0;
 
+	bcache_debug = debugfs_create_dir("bcache", NULL);
 	return IS_ERR_OR_NULL(bcache_debug);
 }