Re: [PATCH 4/5] kernfs: implement kernfs_path_len()

[Tejun Heo <tj@kernel.org>]

Hello, Nioklay.

I restored the cc list.  Please use reply-to-all.

On Wed, Jul 08, 2015 at 11:08:43AM +0300, Nikolay Borisov wrote:
> > +size_t kernfs_path_len(struct kernfs_node *kn)
> > +{
> > +	size_t len = 0;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&kernfs_rename_lock, flags);
> > +
> > +	do {
> > +		len += strlen(kn->name) + 1;
> > +		kn = kn->parent;
> > +	} while (kn && kn->parent);
> > +
> > +	spin_unlock_irqrestore(&kernfs_rename_lock, flags);
> > +
> > +	return len;
> > +}
> > +
> 
> Can you explain the reason why you need to disable the irqs while
> executing this function? Presumably it has to do with the context of its
> usage - tracepoints but I wasn't able to find any information about the
> implications of interrupts being enabled while in a trace point?

It doesn't have much to do with the specific usage.
kernfs_rename_lock is irq-safe because we want to be able to call
functions like kernfs_name() and kernfs_path() regardless of the
current context.

Thanks.

-- 
tejun