Re: [PATCH 2/2] drivers: core: Remove glue dirs from sysfs earlier

[Benjamin Herrenschmidt]

On Sat, 2018-06-30 at 11:04 +1000, Benjamin Herrenschmidt wrote:
> I had a look (see my other email). It's non-trivial. We can still look
> into it, but from what I gathered of how sysfs works, it's based on
> kernfs which doesn't have the kobjects nor access to the reference
> count, and is the holder of the names rbtree.
> 
> So we'd need to find a way to convey that "in-use" information down to
> kernfs (I thought maybe adding an optional pointer to a kref ? but
> then, it's still somewhat racy ...)
> 
> Additionally, we would need a few more pairs of eyes to make sure that
> sticking duplicates in that rbtree isn't going to break some corner
> case in there.

Just to clarify, I will look into it, but it will take more time so I'm
keen on having the low hanging fixes in now.

Also in general, I dislike the idea of leaving things in sysfs with a
refcount of 0. That "late" cleanup in kobject_release() looks to me
more like a band-aid than a feature.

I'd be almost tempted to stick a WARN_ON in there and see who gets hit
but I worry it's going send me down one of those rabbit holes and my
time is limited these days ;-)

Cheers,
Ben.