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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,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 D658FC433C1 for ; Sun, 28 Mar 2021 15:50:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E39061974 for ; Sun, 28 Mar 2021 15:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230196AbhC1PtX (ORCPT ); Sun, 28 Mar 2021 11:49:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229593AbhC1PtK (ORCPT ); Sun, 28 Mar 2021 11:49:10 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50DADC061756; Sun, 28 Mar 2021 08:49:10 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: tonyk) with ESMTPSA id 9D0AA1F4629A Subject: Re: [PATCH 1/3] fs/dcache: Add d_clear_dir_neg_dentries() To: Matthew Wilcox Cc: Alexander Viro , Theodore Ts'o , Andreas Dilger , Jaegeuk Kim , Chao Yu , krisman@collabora.com, kernel@collabora.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Daniel Rosenberg , Chao Yu References: <20210328144356.12866-1-andrealmeid@collabora.com> <20210328144356.12866-2-andrealmeid@collabora.com> <20210328150715.GA33249@casper.infradead.org> From: =?UTF-8?Q?Andr=c3=a9_Almeida?= Message-ID: <74ca03a0-1975-8b9f-f9af-c15946580904@collabora.com> Date: Sun, 28 Mar 2021 12:49:01 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210328150715.GA33249@casper.infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Às 12:07 de 28/03/21, Matthew Wilcox escreveu: > On Sun, Mar 28, 2021 at 11:43:54AM -0300, André Almeida wrote: >> +/** >> + * d_clear_dir_neg_dentries - Remove negative dentries in an inode >> + * @dir: Directory to clear negative dentries >> + * >> + * For directories with negative dentries that are becoming case-insensitive >> + * dirs, we need to remove all those negative dentries, otherwise they will >> + * become dangling dentries. During the creation of a new file, if a d_hash >> + * collision happens and the names match in a case-insensitive, the name of >> + * the file will be the name defined at the negative dentry, that can be >> + * different from the specified by the user. To prevent this from happening, we >> + * need to remove all dentries in a directory. Given that the directory must be >> + * empty before we call this function we are sure that all dentries there will >> + * be negative. >> + */ > > This is quite the landmine of a function. It _assumes_ that the directory > is empty, and clears all dentries in it. > >> +void d_clear_dir_neg_dentries(struct inode *dir) >> +{ >> + struct dentry *alias, *dentry; >> + >> + hlist_for_each_entry(alias, &dir->i_dentry, d_u.d_alias) { >> + list_for_each_entry(dentry, &alias->d_subdirs, d_child) { >> + d_drop(dentry); >> + dput(dentry); >> + } > > I would be happier if it included a check for negativity. d_is_negative() > or maybe this newfangled d_really_is_negative() (i haven't stayed up > to speed on the precise difference between the two) > Makes sense. And given that this only makes sense if the directory is empty, if it founds a non-negative dentry, it should return some error right? >> + } >> +} >> +EXPORT_SYMBOL(d_clear_dir_neg_dentries); > > I'd rather see this _GPL for such an internal thing. >