linux-kernel - Re: [PATCH] eventfs: Process deletion of dentry more thoroughly

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Date:   Wed, 1 Nov 2023 00:16:59 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ajay Kaher <akaher@...are.com>
Subject: Re: [PATCH] eventfs: Process deletion of dentry more thoroughly

On Wed, 1 Nov 2023 02:25:53 +0000
Al Viro <viro@...iv.linux.org.uk> wrote:

> On Tue, Oct 31, 2023 at 02:47:03PM -0400, Steven Rostedt wrote:
> > From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> > 
> > Looking at how dentry is removed via the tracefs system, I found that
> > eventfs does not do everything that it did under tracefs. The tracefs
> > removal of a dentry calls simple_recursive_removal() that does a lot more
> > than a simple d_invalidate().  
> 
> Umm...  Is there any reason not to use simple_recursive_removal() there?

Hmm, I may be able to (I'm still a newbie with understanding of the vfs).

I did it this way thinking that a dentry may exist in the children but not
at a higher level, but I don't think that can be the case. This creates
dentries and inodes dynamically when they are referenced. The eventfs_inode
maps to each directory (the files of a directory are created from the
information from the eventfs_inode).

My thought process for doing it this way was if a child created a dentry
but the parent did not. But I don't think that can happen, right? So all I
may need to do is to check if the ei->dentry exists for the ei that is
being deleted, and after marking it and all its children as "freed", I can
then call simple_recursive_removal() on the top ei->dentry if it exists, as
that will guarantee to get all the dentries of any of the children that
exist. Right?

-- Steve