Re: [PATCH 6/7] kernfs: Allow kernfs nodes to be deactivated and re-activated

Tejun Heo
2022-08-23T20:41:56Z

Hello,

On Tue, Aug 23, 2022 at 01:49:07PM +0800, Chengming Zhou wrote:
> > - if (pos->flags & KERNFS_ACTIVATED)
> > + if (kernfs_active(pos) || (kn->flags & KERNFS_REMOVING))
>
> May I ask a question, what's the difference between kernfs_active() and KERNFS_ACTIVATED?
>
> KERNFS_ACTIVATED is always set when kernfs_activate() and never clear, so I think it means:
>
> 1. !KERNFS_ACTIVATED : allocated but not activated
> 2. KERNFS_ACTIVATED && !kernfs_active() : make deactivated by kernfs_deactivate_locked()
>
> I see most code check kernfs_active(), but two places check KERNFS_ACTIVATED, I'm not sure where
> should check KERNFS_ACTIVATED, or is there any chance we can remove KERNFS_ACTIVATED?

Yeah, ACTIVATED means taht created but never activated while kernfs_active()
means currently active. I tried to substitute all ACTIVATED tests with
kernfs_active() and remove the former but I wasn't sure about changing
kernfs_add_one() behavior.

I think it's too confusing to combine the initial activated state with
user-requested show/hide state and causes other problems like
kernfs_activate() used to activate newly created files unhiding files
explicitly deactivated. Lemme separate out show/hide state into something
separate so that the distinction is clear.

Thanks.

--
tejun