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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF0A0C433F5 for ; Mon, 4 Oct 2021 06:15:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AAF036136F for ; Mon, 4 Oct 2021 06:15:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232701AbhJDGQt (ORCPT ); Mon, 4 Oct 2021 02:16:49 -0400 Received: from zeniv-ca.linux.org.uk ([142.44.231.140]:33082 "EHLO zeniv-ca.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232131AbhJDGQs (ORCPT ); Mon, 4 Oct 2021 02:16:48 -0400 Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mXHDQ-009pZz-IU; Mon, 04 Oct 2021 06:12:44 +0000 Date: Mon, 4 Oct 2021 06:12:44 +0000 From: Al Viro To: Greg Kroah-Hartman Cc: Ian Kent , Tejun Heo , Hou Tao , David Howells , Miklos Szeredi , Rick Lindsley , Carlos Maiolino , linux-fsdevel , Kernel Mailing List Subject: Re: [REPOST,UPDATED PATCH] kernfs: don't create a negative dentry if inactive node exists Message-ID: References: <163330943316.19450.15056895533949392922.stgit@mickey.themaw.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 04, 2021 at 08:03:55AM +0200, Greg Kroah-Hartman wrote: > On Mon, Oct 04, 2021 at 01:07:46AM +0000, Al Viro wrote: > > On Mon, Oct 04, 2021 at 09:03:53AM +0800, Ian Kent wrote: > > > It's been reported that doing stress test for module insertion and > > > removal can result in an ENOENT from libkmod for a valid module. > > > > > > In kernfs_iop_lookup() a negative dentry is created if there's no kernfs > > > node associated with the dentry or the node is inactive. > > > > > > But inactive kernfs nodes are meant to be invisible to the VFS and > > > creating a negative dentry for these can have unexpected side effects > > > when the node transitions to an active state. > > > > > > The point of creating negative dentries is to avoid the expensive > > > alloc/free cycle that occurs if there are frequent lookups for kernfs > > > attributes that don't exist. So kernfs nodes that are not yet active > > > should not result in a negative dentry being created so when they > > > transition to an active state VFS lookups can create an associated > > > dentry is a natural way. > > > > > > It's also been reported that https://github.com/osandov/blktests.git > > > test block/001 hangs during the test. It was suggested that recent > > > changes to blktests might have caused it but applying this patch > > > resolved the problem without change to blktests. > > > > Looks sane, but which tree should it go through? I can pick it, but I've > > no idea if anybody already has kernfs work in their trees... > > I can take it, kernfs patches normally go through my tree, can I get an > acked-by? ACKed-by: Al Viro