Re: [PATCH] Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs

[Li Zefan <lizf@cn.fujitsu.com>]

>>> Subject: [PATCH] Add missing blk_trace_remove_sysfs to be in pair with
>>> blk_trace_init_sysfs
>>> From: Zdenek Kabelac <zkabelac@redhat.com>
>>>
>>> Adds missing blk_trace_remove_sysfs() to be in pair with
>>> blk_trace_init_sysfs() introduced in commit
>>> 1d54ad6da9192fed5dd3b60224d9f2dfea0dcd82.
>>>
>>> Problem was noticed via kmemleak backtrace when some sysfs entries
>>> were note properly destroyed during  device removal:
>>>
>> Thanks for reporting and fixing this!
>>
>>> @@ -465,6 +466,7 @@ void blk_unregister_queue(struct gendisk *disk)
>>>
>>>               kobject_uevent(&q->kobj, KOBJ_REMOVE);
>>>               kobject_del(&q->kobj);
>>> +             blk_trace_remove_sysfs(disk_to_dev(disk));
>> This should be moved outside of 'if'.
>>
> 
> I was not really sure about the proper place - if it could be placed
> before if() or after the if(){} - as I've not checked in depth

Just use the reverse order against blk_register_queue() should be fine.

> connection between kobj and sysfs. It's somewhat unclear why all the
> kobject operation are only within this if(){} block - so I've thought
> there is some reason...
> IMHO only elv_unregister_queue() should be probably in the if(){} block.
> 

Seems it's a bug to put kobject_put(dev->kobj) in the if block.

I created a stacked device (mdadm) and kmemleak still reported leaks
even after I fixed the blktrace issue. And then I moved kobejct_put()
outside the if, no more leaks reports.

> Feel free to update/fix.
>