Re: [RFC PATCH V2] tracing: Check f_dentry before accessingevent_file/call in inode->i_private

From: Oleg Nesterov
Date: Wed Jul 17 2013 - 10:57:27 EST


On 07/17, Masami Hiramatsu wrote:
>
> (2013/07/16 3:16), Oleg Nesterov wrote:
> > On 07/09, Masami Hiramatsu wrote:
> >>
> >> To avoid this, when opening events/*/*/enable, we have to ensure
> >> the dentry of the file is not unlinked yet, under event_mutex
> >> is locked.
> >
> > Probably this can work, but I am starting to think that this ref
> > count becomes toooooo complex....
>
> Oleg, I agree that is a bit complex way to fix but it can fix.
>
> However, I think we should fix bugs first, because there are bugs.
> I don't like to leave a bug in the kernel as it is, while we re-
> start discussing new approach...

And I am trying to fix the same problems, just _I think_ there is
another and simpler approach.

> So, I'd like to suggest you getting these fixes into ftrace as
> first-aid treatment, and discuss your new series.

Well, perhaps you are right... But this TRACE_EVENT_FL_REF_MASK code
is new too, it is not that we only need a small fixlets to finish it.

So I think that it makes sense to discuss the alternatives before we
decide what exactly we should do.

Oleg.

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