Re: [BUG] -next lockdep invalid wait context

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2024-11-08 07:02:24 [-1000], Tejun Heo wrote:
> Hello,
Hi,

> > @@ -223,12 +226,11 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
> >  int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
> >  			  char *buf, size_t buflen)
> >  {
> > -	unsigned long flags;
> >  	int ret;
> >  
> > -	read_lock_irqsave(&kernfs_rename_lock, flags);
> > +	rcu_read_lock();
> >  	ret = kernfs_path_from_node_locked(to, from, buf, buflen);
> > -	read_unlock_irqrestore(&kernfs_rename_lock, flags);
> > +	rcu_read_unlock();
> >  	return ret;
> >  }
> 
> The _locked suffix looks awkward afterwards. Given that there's no
> restriction on how the function is called anymore, maybe we can just
> collapse _locked bodies into the callers?

Sure.

> ...
> > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> > index 87c79d076d6d7..733d89de40542 100644
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -199,8 +199,8 @@ struct kernfs_node {
> >  	 * never moved to a different parent, it is safe to access the
> >  	 * parent directly.
> >  	 */
> > -	struct kernfs_node	*parent;
> > -	const char		*name;
> > +	struct kernfs_node	__rcu *parent;
> > +	const char		__rcu *name;
> 
> ->parent doesn't have to be converted to RCU. As long as the node is
> accessible, the parent is guaranteed to be pinned and unchanged. We only
> need to RCUfy ->name.

I was uncertain about parent. But in that case, let me keep parent as-is
and just do name.
Thanks.

> Thanks.
> 

Sebastian