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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 52C85C48BD1 for ; Fri, 11 Jun 2021 12:50:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BE55613D3 for ; Fri, 11 Jun 2021 12:50:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231266AbhFKMwy (ORCPT ); Fri, 11 Jun 2021 08:52:54 -0400 Received: from mail-vs1-f42.google.com ([209.85.217.42]:34424 "EHLO mail-vs1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230233AbhFKMww (ORCPT ); Fri, 11 Jun 2021 08:52:52 -0400 Received: by mail-vs1-f42.google.com with SMTP id q2so3689314vsr.1 for ; Fri, 11 Jun 2021 05:50:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zbkj6T3T04z4JtJ0EN+yh0xReBYxOd5BeJrygN3ZyFY=; b=ZfzqvA87eAWrqj09uQ4GZgIXoBXccSg3LsgcMTGU218ej3xJW33GsxTxpHsa+Nmd+g TgP6Gi73TFHtlWaexLEsM/qBkIZ1AAaaKm4CHcjCmd6upG/IJkwmGUyahkzQspo+GD8c GouQVLzFTXA6ABz44/LJySj42I1eSqG5qBcLk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zbkj6T3T04z4JtJ0EN+yh0xReBYxOd5BeJrygN3ZyFY=; b=t8se4kvCcLdX/Yqg6fMwXpziFDRpdDGoPLlB0iQnpb130gZ7S+8CF68wr0IXDOOtkv uLtzi1qkXMIZz/UoUX8h4xMh5GHrU9ByNaIh14kuA0ouTexvlzCdLMCOboF9DTK3PudR l+i5Ocv7lzTghi6MK6pEK79XJLNFGtyOMkySPi2ldSmjUa7KAJyAbrFiFsCtMn0WPoM9 a1Jr6KH/ok5ZkGUVjBN9rYqHePqgkGpDaI5uMtsmmP47l3PbHZEebPoPEJBcfxk6NcRH QOhxEDnSRspLnz9UHNT+v33DG5dFQM1wtuS1zLnLvT1iDAL2Ok87csI2PS9beqbIkMVu h1dw== X-Gm-Message-State: AOAM531cqcYHx9Xv/osBUQKqGmRAoR+m9NDu6dfZSGRURYDCQCCks7dN 9Fqx4vlFbuF8oDKToC/NW6uIqzf/xiklmxlY1jABdA== X-Google-Smtp-Source: ABdhPJw0DFrogEnGKXGUiNWZJkVClfZ9iOeK7L+TRdy022jkFc4LsDLAOKTMDsQKzgM8449FfUWM88Z7NtNavVP17ag= X-Received: by 2002:a67:ffcc:: with SMTP id w12mr9555466vsq.47.1623415794229; Fri, 11 Jun 2021 05:49:54 -0700 (PDT) MIME-Version: 1.0 References: <162322846765.361452.17051755721944717990.stgit@web.messagingengine.com> <162322859985.361452.14110524195807923374.stgit@web.messagingengine.com> In-Reply-To: <162322859985.361452.14110524195807923374.stgit@web.messagingengine.com> From: Miklos Szeredi Date: Fri, 11 Jun 2021 14:49:43 +0200 Message-ID: Subject: Re: [PATCH v6 2/7] kernfs: add a revision to identify directory node changes To: Ian Kent Cc: Greg Kroah-Hartman , Tejun Heo , Eric Sandeen , Fox Chen , Brice Goglin , Al Viro , Rick Lindsley , David Howells , Marcelo Tosatti , "Eric W. Biederman" , Carlos Maiolino , linux-fsdevel , Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Jun 2021 at 10:50, Ian Kent wrote: > > 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 > --- > fs/kernfs/dir.c | 2 ++ > fs/kernfs/kernfs-internal.h | 23 +++++++++++++++++++++++ > include/linux/kernfs.h | 5 +++++ > 3 files changed, 30 insertions(+) > > diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c > index 33166ec90a112..b3d1bc0f317d0 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 ccc3b44f6306f..b4e7579e04799 100644 > --- a/fs/kernfs/kernfs-internal.h > +++ b/fs/kernfs/kernfs-internal.h > @@ -81,6 +81,29 @@ 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 *kn, > + struct dentry *dentry) > +{ > + if (kernfs_type(kn) == KERNFS_DIR) > + dentry->d_time = kn->dir.rev; > +} > + > +static inline void kernfs_inc_rev(struct kernfs_node *kn) > +{ > + if (kernfs_type(kn) == KERNFS_DIR) > + kn->dir.rev++; > +} > + > +static inline bool kernfs_dir_changed(struct kernfs_node *kn, > + struct dentry *dentry) > +{ > + if (kernfs_type(kn) == KERNFS_DIR) { Aren't these always be called on a KERNFS_DIR node? You could just reduce that to a WARN_ON, or remove the conditions altogether then. Thanks, Miklos