From patchwork Fri Jul 16 09:28:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Kent X-Patchwork-Id: 12381809 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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 8ACFAC07E95 for ; Fri, 16 Jul 2021 09:37:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6BE00613D8 for ; Fri, 16 Jul 2021 09:37:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233772AbhGPJk1 (ORCPT ); Fri, 16 Jul 2021 05:40:27 -0400 Received: from icp-osb-irony-out9.external.iinet.net.au ([203.59.1.226]:22594 "EHLO icp-osb-irony-out9.external.iinet.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229833AbhGPJk0 (ORCPT ); Fri, 16 Jul 2021 05:40:26 -0400 X-Greylist: delayed 556 seconds by postgrey-1.27 at vger.kernel.org; Fri, 16 Jul 2021 05:40:26 EDT X-SMTP-MATCH: 0 IronPort-HdrOrdr: A9a23:TyZQ4a2U2q0zHeqTam8V0QqjBLIkLtp133Aq2lEZdPRUGvb3qynIpoV+6faUskd1ZJhOo7290cW7LU80lqQFg7X5X43SOzUO0VHAROoJ0WKL+UyHJ8SUzI5gPMlbHJSWcOeAbmSS9vya3DWF X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2AdBwA6UPFg/y2ELHlQCh4BAQsSDEAJgUULAoN2bIQCRpATAQEBAQEBBowphW9fiikUgWgLAQEBAQEBAQEBSgQBAYRUAoJ8ASU0CQ4CBBUBAQEFAQEBAQEGAwGBDoV1QwEMAYV1BiMEUhAYDQIRBw4CAkcQBgEShVMlp2d/MxoCZYpDgRAqAYcIgmiDeiccfYEQgUgDgy2DfRpsgliCZASDGIEPNHyBD5UMAUaKGVudDIMunmQXlU8DkHWWCKcOghRNLgqDJFAZjjkWjjo3LzgCBgoBAQMJgnKHIieCHgEB X-IPAS-Result: A2AdBwA6UPFg/y2ELHlQCh4BAQsSDEAJgUULAoN2bIQCRpATAQEBAQEBBowphW9fiikUgWgLAQEBAQEBAQEBSgQBAYRUAoJ8ASU0CQ4CBBUBAQEFAQEBAQEGAwGBDoV1QwEMAYV1BiMEUhAYDQIRBw4CAkcQBgEShVMlp2d/MxoCZYpDgRAqAYcIgmiDeiccfYEQgUgDgy2DfRpsgliCZASDGIEPNHyBD5UMAUaKGVudDIMunmQXlU8DkHWWCKcOghRNLgqDJFAZjjkWjjo3LzgCBgoBAQMJgnKHIieCHgEB X-IronPort-AV: E=Sophos;i="5.84,244,1620662400"; d="scan'208";a="329873560" Received: from unknown (HELO web.messagingengine.com) ([121.44.132.45]) by icp-osb-irony-out9.iinet.net.au with ESMTP; 16 Jul 2021 17:28:19 +0800 Subject: [PATCH v8 1/5] kernfs: add a revision to identify directory node changes From: Ian Kent To: Greg Kroah-Hartman , Tejun Heo Cc: Eric Sandeen , Fox Chen , Brice Goglin , Al Viro , Rick Lindsley , David Howells , Miklos Szeredi , Marcelo Tosatti , "Eric W. Biederman" , Carlos Maiolino , linux-fsdevel , Kernel Mailing List Date: Fri, 16 Jul 2021 17:28:18 +0800 Message-ID: <162642769895.63632.8356662784964509867.stgit@web.messagingengine.com> In-Reply-To: <162642752894.63632.5596341704463755308.stgit@web.messagingengine.com> References: <162642752894.63632.5596341704463755308.stgit@web.messagingengine.com> User-Agent: StGit/0.23 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a revision counter to kernfs directory nodes so it can be used to detect if a directory node has changed during negative dentry revalidation. There's an assumption that sizeof(unsigned long) <= sizeof(pointer) on all architectures and as far as I know that assumption holds. So adding a revision counter to the struct kernfs_elem_dir variant of the kernfs_node type union won't increase the size of the kernfs_node struct. This is because struct kernfs_elem_dir is at least sizeof(pointer) smaller than the largest union variant. It's tempting to make the revision counter a u64 but that would increase the size of kernfs_node on archs where sizeof(pointer) is smaller than the revision counter. Signed-off-by: Ian Kent Reviewed-by: Miklos Szeredi --- fs/kernfs/dir.c | 2 ++ fs/kernfs/kernfs-internal.h | 19 +++++++++++++++++++ include/linux/kernfs.h | 5 +++++ 3 files changed, 26 insertions(+) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 33166ec90a11..b3d1bc0f317d 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -372,6 +372,7 @@ static int kernfs_link_sibling(struct kernfs_node *kn) /* successfully added, account subdir number */ if (kernfs_type(kn) == KERNFS_DIR) kn->parent->dir.subdirs++; + kernfs_inc_rev(kn->parent); return 0; } @@ -394,6 +395,7 @@ static bool kernfs_unlink_sibling(struct kernfs_node *kn) if (kernfs_type(kn) == KERNFS_DIR) kn->parent->dir.subdirs--; + kernfs_inc_rev(kn->parent); rb_erase(&kn->rb, &kn->parent->dir.children); RB_CLEAR_NODE(&kn->rb); diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index ccc3b44f6306..c2ae58f3b202 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -81,6 +81,25 @@ static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry) return d_inode(dentry)->i_private; } +static inline void kernfs_set_rev(struct kernfs_node *parent, + struct dentry *dentry) +{ + dentry->d_time = parent->dir.rev; +} + +static inline void kernfs_inc_rev(struct kernfs_node *parent) +{ + parent->dir.rev++; +} + +static inline bool kernfs_dir_changed(struct kernfs_node *parent, + struct dentry *dentry) +{ + if (parent->dir.rev != dentry->d_time) + return true; + return false; +} + extern const struct super_operations kernfs_sops; extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache; diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 9e8ca8743c26..d68b4ad09573 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -98,6 +98,11 @@ struct kernfs_elem_dir { * better directly in kernfs_node but is here to save space. */ struct kernfs_root *root; + /* + * Monotonic revision counter, used to identify if a directory + * node has changed during negative dentry revalidation. + */ + unsigned long rev; }; struct kernfs_elem_symlink {