On Mon, Oct 30, 2017 at 02:10:16PM +0100, Jan Kara wrote:

On Fri 27-10-17 01:36:14, weiping zhang wrote:

quoted

In order to make error handle more cleaner we call bdi_debug_register
before set state to WB_registered, that we can avoid call bdi_unregister
in release_bdi().

Signed-off-by: weiping zhang <redacted>
---
 mm/backing-dev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e9d6a1ede12b..54396d53f471 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c

@@ -893,10 +893,13 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 	if (IS_ERR(dev))
 		return PTR_ERR(dev);
 
+	if (bdi_debug_register(bdi, dev_name(dev))) {
+		device_destroy(bdi_class, dev->devt);
+		return -ENOMEM;
+	}
 	cgwb_bdi_register(bdi);
 	bdi->dev = dev;
 
-	bdi_debug_register(bdi, dev_name(dev));
 	set_bit(WB_registered, &bdi->wb.state);
 
 	spin_lock_bh(&bdi_lock);

@@ -916,6 +919,8 @@ int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
 	va_start(args, fmt);
 	ret = bdi_register_va(bdi, fmt, args);
 	va_end(args);
+	if (ret)
+		bdi_put(bdi);

Why do you drop bdi reference here in case of error? We didn't do it
previously if bdi_register_va() failed for other reasons...

At first I want add cleanup, because
device_add_disk->bdi_register_owner->bdi_register doen't do clanup. But
I notice that mtd_bdi_init also call bdi_register and do cleanup, so
this bdi_put() is wrong. I'll remove it at V2. Thanks a lot.

--
weiping