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_1 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 84B2FC432C3 for ; Fri, 15 Nov 2019 13:49:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68F2820733 for ; Fri, 15 Nov 2019 13:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727509AbfKONs4 (ORCPT ); Fri, 15 Nov 2019 08:48:56 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:60950 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727417AbfKONs4 (ORCPT ); Fri, 15 Nov 2019 08:48:56 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iVbxX-0001U0-6B; Fri, 15 Nov 2019 13:48:23 +0000 Date: Fri, 15 Nov 2019 13:48:23 +0000 From: Al Viro To: Steven Rostedt 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: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191115083813.65f5523c@gandalf.local.home> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Nov 15, 2019 at 08:38:13AM -0500, Steven Rostedt wrote: > On Fri, 15 Nov 2019 13:16:25 +0000 > Al Viro wrote: > > > I want to understand the overall situation. No argument, list_empty() > > in there is BS, for many reasons. But I wonder if trying to keep the > > current structure of the iterator _and_ the use of simple_rmdir()/simple_unlink() > > is the right approach. > > My guess is that debugfs was written to be as simple as possible. > Nothing too complex. And in doing so, may have issues as you are > pointing out. Just a way to allow communications between user space and > kernel space (as tracefs started out). > > 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.