From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E8BBC433F5 for ; Fri, 4 Mar 2022 22:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230015AbiCDW5z (ORCPT ); Fri, 4 Mar 2022 17:57:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229931AbiCDW5s (ORCPT ); Fri, 4 Mar 2022 17:57:48 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFC9122FD92 for ; Fri, 4 Mar 2022 14:56:57 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8FF7861E92 for ; Fri, 4 Mar 2022 22:56:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A34ECC340E9; Fri, 4 Mar 2022 22:56:56 +0000 (UTC) Date: Fri, 4 Mar 2022 17:56:55 -0500 From: Steven Rostedt To: lsf-pc@lists.linux-foundation.org Cc: linux-fsdevel@vger.kernel.org Subject: [LSF/MM/BPF TOPIC] Dynamic allocation of pseudo file systems Message-ID: <20220304175655.055dcdde@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org At the 2021 Linux Plumbers Tracing Microconference there was a discussionon creating just-in-time dentrys for pseudo file systems (the tracing one was about the events directory in tracefs). https://lpc.events/event/11/contributions/1085/attachments/855/1668/Eventfs_split_v15.pdf https://www.youtube.com/watch?v=jsxuVI7Wav0&list=PLVsQ_xZBEyN3wA8Ej4BUjudXFbXuxhnfc&t=7561s At the microconference there was also interest in extending this to other pseudo file systems like /sys and /proc. The rationale for this is due to the fact that the dentrys take up a lot of memory, and there's no reason to have them if nobody is looking at them. Having a way to create them at the time the user looks at/enters the directory would save quite a bit. But there may be issues. What happens if there's no memory to allocate? Our focus was on just working with the tracefs file system, but I would like to discuss how we could make this into a generic feature that any pseudo file system can use, and discuss what issues could arise by it, and how to mitigate those issues. Sorry, for the delay in posting. I understand that the deadline has just passed, but starting a new job had caused me to not pay attention and I missed it. Hopefully, you can still consider this. -- Steve