From patchwork Fri Nov 15 03:27:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 11244737 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AE73213BD for ; Fri, 15 Nov 2019 03:20:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97B57206F4 for ; Fri, 15 Nov 2019 03:20:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727276AbfKODUq (ORCPT ); Thu, 14 Nov 2019 22:20:46 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:6671 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726549AbfKODUl (ORCPT ); Thu, 14 Nov 2019 22:20:41 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 2D31FEB4961799FCF945; Fri, 15 Nov 2019 11:20:38 +0800 (CST) Received: from huawei.com (10.90.53.225) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Fri, 15 Nov 2019 11:20:29 +0800 From: yu kuai To: , , , , , , , , CC: , , , , , , Subject: [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class' Date: Fri, 15 Nov 2019 11:27:50 +0800 Message-ID: <1573788472-87426-2-git-send-email-yukuai3@huawei.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> References: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.90.53.225] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 'dentry_d_lock_class' can be used for spin_lock_nested in case lockdep confused about two different dentry take the 'd_lock'. However, a single 'DENTRY_D_LOCK_NESTED' may not be enough if more than two dentry are involed. So, and in 'DENTRY_D_LOCK_NESTED_2' Signed-off-by: yu kuai --- include/linux/dcache.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 10090f1..8eb84ef 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -129,7 +129,8 @@ struct dentry { enum dentry_d_lock_class { DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ - DENTRY_D_LOCK_NESTED + DENTRY_D_LOCK_NESTED, + DENTRY_D_LOCK_NESTED_2 }; struct dentry_operations { From patchwork Fri Nov 15 03:27:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 11244735 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9B7581393 for ; Fri, 15 Nov 2019 03:20:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D85620729 for ; Fri, 15 Nov 2019 03:20:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727202AbfKODUl (ORCPT ); Thu, 14 Nov 2019 22:20:41 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:6674 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727189AbfKODUk (ORCPT ); Thu, 14 Nov 2019 22:20:40 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 3B8F0C2FC6BF8129BBC7; Fri, 15 Nov 2019 11:20:38 +0800 (CST) Received: from huawei.com (10.90.53.225) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Fri, 15 Nov 2019 11:20:29 +0800 From: yu kuai To: , , , , , , , , CC: , , , , , , Subject: [PATCH 2/3] fs/libfs.c: use 'spin_lock_nested' when taking 'd_lock' for dentry in simple_empty Date: Fri, 15 Nov 2019 11:27:51 +0800 Message-ID: <1573788472-87426-3-git-send-email-yukuai3@huawei.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> References: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.90.53.225] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org simple_emtpty currently use 'spin_lock_nested' for 'child' to avoid confusion for lockdep. However, it's not used for 'dentry'. In that case, there will be a problem if the caller called 'simple_empty' with a parent's 'd_lock' held: spin_lock(&dentry->d_parent->d_lock) call simple_empty(dentry) spin_lock(&dentry->d_lock) --> lockdep will report this spin_lock_nested(child->d_lock, spin_lock_nested) spin_unlock(child_lock) spin_unlock($dentry->d_lock) return from simple_empty spin_unlock(&dentry->d_patrent->d_lock) So, use 'DENTRY_D_LOCK_NESTED' for 'dentry' and 'spin_lock_nested_2' for child. Signed-off-by: yu kuai --- fs/libfs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/libfs.c b/fs/libfs.c index 1463b03..62e9ba9 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -336,9 +336,9 @@ int simple_empty(struct dentry *dentry) struct dentry *child; int ret = 0; - spin_lock(&dentry->d_lock); + spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); list_for_each_entry(child, &dentry->d_subdirs, d_child) { - spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); + spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED_2); if (simple_positive(child)) { spin_unlock(&child->d_lock); goto out; From patchwork Fri Nov 15 03:27:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 11244739 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6FFAA13BD for ; Fri, 15 Nov 2019 03:20:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5074D206F4 for ; Fri, 15 Nov 2019 03:20:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727217AbfKODUl (ORCPT ); Thu, 14 Nov 2019 22:20:41 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:6673 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727192AbfKODUk (ORCPT ); Thu, 14 Nov 2019 22:20:40 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 34467167B78BBFEC3706; Fri, 15 Nov 2019 11:20:38 +0800 (CST) Received: from huawei.com (10.90.53.225) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Fri, 15 Nov 2019 11:20:30 +0800 From: yu kuai To: , , , , , , , , CC: , , , , , , Subject: [PATCH 3/3] debugfs: fix potential infinite loop in debugfs_remove_recursive Date: Fri, 15 Nov 2019 11:27:52 +0800 Message-ID: <1573788472-87426-4-git-send-email-yukuai3@huawei.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> References: <1573788472-87426-1-git-send-email-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.90.53.225] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org debugfs_remove_recursive uses list_empty to judge weather a dentry has any subdentry or not. This can lead to infinite loop when any subdir is in use. The problem was discoverd by the following steps in the console. 1. use debugfs_create_dir to create a dir and multiple subdirs(insmod); 2. cd to the subdir with depth not less than 2; 3. call debugfs_remove_recursive(rmmod). After removing the subdir, the infinite loop is triggered because debugfs_remove_recursive uses list_empty to judge if the current dir doesn't have any subdentry. However list_empty can't skip the subdentry that is not simple_positive(simple_positive() will return false). Fix the problem by using simple_empty instead of list_empty. Fixes: 776164c1faac ('debugfs: debugfs_remove_recursive() must not rely on list_empty(d_subdirs)') Reported-by: chenxiang66@hisilicon.com Signed-off-by: yu kuai --- fs/debugfs/inode.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index 7b975db..d64608276 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -773,8 +773,11 @@ void debugfs_remove_recursive(struct dentry *dentry) if (!simple_positive(child)) continue; - /* perhaps simple_empty(child) makes more sense */ - if (!list_empty(&child->d_subdirs)) { + /* + * use simple_empty to prevent infinite loop when any + * subdentry of child is in use + */ + if (!simple_empty(child)) { spin_unlock(&parent->d_lock); inode_unlock(d_inode(parent)); parent = child;