Hi Michael and Jens When I do back port of bcache patches, I find commit 539d39eb2708 ("bcache: fix wrong return value in bch_debug_init()") has extra part from the original patch which Junhui Tanng posted. The patch posted by Junhui Tang was, From: Tang Junhui <tang.junhui@xxxxxxxxxx> in bch_debug_init(), ret is always 0, and the return value is useless, change it to return 0 if be success after calling debugfs_create_dir(), else return a non-zero value. Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx> --- drivers/md/bcache/debug.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c index c7a02c4..2bb0b28 --- a/drivers/md/bcache/debug.c +++ b/drivers/md/bcache/debug.c @@ -251,8 +251,7 @@ void bch_debug_exit(void) int __init bch_debug_init(struct kobject *kobj) { - int ret = 0; - debug = debugfs_create_dir("bcache", NULL); - return ret; + + return IS_ERR_OR_NULL(debug); } But the patch merged in 4.16 has extra part of writeback stuffs. I guess maybe some two patches combined together unwittingly. Michael, could you please give me some hint ? Should we remove the extra part of this patch, or we should split them into two patches ? Thanks. Coly Li