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

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Message-ID: <CAHk-=wiNY3W1QKveFnH=dJtRNW7kA1Nbn6Ua49EbM6AC+Rx8wg@mail.gmail.com>
Date: Tue, 30 Jan 2024 08:55:51 -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 08:49, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> - On removal, I got rid of the SRCU callback and the work queue.
>   Instead, I find the dentry of the current eventfs_inode that is being
>   deleted by walking the ei->parent until I find the events inode that has
>   a dentry. I then use that to do a lookup walking back down to the
>   eventfs_inode I want to delete. This gives me the dentry that I can call
>   d_invalidate() on.

Yes, that works.

However, I have a patch that is *much* smaller and simpler, and
doesn't need that walk.

The VFS layer already has a good interface for "should I still use
this dentry", which is needed for various network filesystems etc that
want to time out caches (or check explicitly whether the file still
exists etc): it's the dentry d_revalidate() check.

Let me just reboot into it to test that I got all the cases.

It makes the code even more obvious, and avoids all the complexity.

           Linus