linux-kernel - Re: [PATCH 5/6] eventfs: get rid of dentry pointers without refcounts

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Message-ID: <CAHk-=wg69FE2826EokkCbSKHZvCG-cM5t=9SMFLcfpNu8Yvwqw@mail.gmail.com>
Date: Tue, 30 Jan 2024 21:57:26 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] eventfs: get rid of dentry pointers without refcounts

On Tue, 30 Jan 2024 at 21:33, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> With even the last patch included, without the d_invalidate() I get errors
> with simply doing:
>
>  # cd /sys/kernel/tracing
>  # mkdir instances/foo
>  # ls instances/foo/events
>  # rmdir instances/foo
>
> As the rmdir calls tracefs_remove() that calls simple_recursive_removal()
> that then walks into the "events" directory. Without that d_invalidate, it
> walks beyond just the top directory and then splats on the dentries that
> are cached.

Ugh.

This is only an issue for that "events" dir, right? The one that has a
proper refcount on the dentry in 'ei->events_dir'?

Because yes, then doing d_invalidate() looks like the right thing.

           Linus