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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96A7EC432C3 for ; Fri, 15 Nov 2019 13:58:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 690912073B for ; Fri, 15 Nov 2019 13:58:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727728AbfKON6J (ORCPT ); Fri, 15 Nov 2019 08:58:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:39068 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727412AbfKON6J (ORCPT ); Fri, 15 Nov 2019 08:58:09 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E61C20733; Fri, 15 Nov 2019 13:58:07 +0000 (UTC) Date: Fri, 15 Nov 2019 08:58:05 -0500 From: Steven Rostedt To: Al Viro Cc: Greg KH , yu kuai , rafael@kernel.org, oleg@redhat.com, mchehab+samsung@kernel.org, corbet@lwn.net, tytso@mit.edu, jmorris@namei.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, zhengbin13@huawei.com, yi.zhang@huawei.com, chenxiang66@hisilicon.com, xiexiuqi@huawei.com Subject: Re: [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class' Message-ID: <20191115085805.008870cb@gandalf.local.home> In-Reply-To: <20191115134823.GQ26530@ZenIV.linux.org.uk> References: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> <1573788472-87426-2-git-send-email-yukuai3@huawei.com> <20191115032759.GA795729@kroah.com> <20191115041243.GN26530@ZenIV.linux.org.uk> <20191115072011.GA1203354@kroah.com> <20191115131625.GO26530@ZenIV.linux.org.uk> <20191115083813.65f5523c@gandalf.local.home> <20191115134823.GQ26530@ZenIV.linux.org.uk> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 15 Nov 2019 13:48:23 +0000 Al Viro wrote: > > BTW, what do you mean by "can debugfs_remove_recursive() rely upon the > > lack of attempts to create new entries inside the subtree it's trying > > to kill?" > > Is it possible for something to call e.g. debugfs_create_dir() (or any > similar primitive) with parent inside the subtree that has been > passed to debugfs_remove_recursive() call that is still in progress? > > If debugfs needs to cope with that, debugfs_remove_recursive() needs > considerably heavier locking, to start with. I don't know about debugfs, but at least tracefs (which cut and pasted from debugfs) does not allow that. At least in theory it doesn't allow that (and if it does, it's a bug in the locking at the higher levels). And perhaps debugfs shouldn't allow that either. As it is only suppose to be a light weight way to interact with the kernel, hence the name "debugfs". Yu, do you have a test case for the "infinite loop" case? -- Steve