linux-kernel - Re: [linus:master] [eventfs] 852e46e239: BUG:unable_to_handle_page_fault_for

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Message-ID: <CAHk-=whe_qeQVrz9=pVjCNVva8+OOJjmrpCj5CiHW3QStUf+6w@mail.gmail.com>
Date: Tue, 30 Jan 2024 08:51:25 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: kernel test robot <oliver.sang@...el.com>, oe-lkp@...ts.linux.dev, lkp@...el.com, 
	linux-kernel@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Christian Brauner <brauner@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, 
	Ajay Kaher <ajay.kaher@...adcom.com>, linux-trace-kernel@...r.kernel.org
Subject: Re: [linus:master] [eventfs] 852e46e239: BUG:unable_to_handle_page_fault_for_address

On Tue, 30 Jan 2024 at 06:39, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 30 Jan 2024 01:12:05 -0800
> >
> > I suspect the solution is to make eventfs_create_dir() do the same as
> > the events directory case does, and actually pin the directory dentry
> > and save it off.
>
> I rather not have the create do that because that happens for every event
> directory.

I wasn't thinking straight yesterday - the real fix is to just do a
"d_revalidate()". It's literally why that thing exists: check whether
a dentry is still valid.

In fact, that trivially gets rid of the 'events' subdirectory issues
too, so we can stop doing that horrendous simple_recursive_removal()
too.

Let me reboot into the trivial fix. I just needed to think about this
the right way.

None of this is anything that the VFS layer has any problems with.

               Linus