From patchwork Tue Mar 31 00:54:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Kent X-Patchwork-Id: 11466567 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 D67EC913 for ; Tue, 31 Mar 2020 00:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE55420748 for ; Tue, 31 Mar 2020 00:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729777AbgCaAyh (ORCPT ); Mon, 30 Mar 2020 20:54:37 -0400 Received: from icp-osb-irony-out4.external.iinet.net.au ([203.59.1.220]:54880 "EHLO icp-osb-irony-out4.external.iinet.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729358AbgCaAyh (ORCPT ); Mon, 30 Mar 2020 20:54:37 -0400 X-SMTP-MATCH: 0 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2DKBAA4lIJe/+im0XZgBh4BCxyBcAuCKYFAIRIqhBqPTgEBAQMGgRKKIIUUhRWFKRSBZwoBAQEBAQEBAQEbGQECBAEBhEQCgjIkNgcOAhABAQEFAQEBAQEFAwFthQpYhXEGIwRSEBgNAhgOAgJHEAYThX4krXh/MxoCiimBDiqMMRp5gQeBRAOBNoFmhDQKgyKCXgSNc4MDhw9FgQCXG4JGlxUdj0IDjCctpnGFfwQugVhNLgqDJ1AYnH83MIEGAQGNJl8BAQ X-IPAS-Result: A2DKBAA4lIJe/+im0XZgBh4BCxyBcAuCKYFAIRIqhBqPTgEBAQMGgRKKIIUUhRWFKRSBZwoBAQEBAQEBAQEbGQECBAEBhEQCgjIkNgcOAhABAQEFAQEBAQEFAwFthQpYhXEGIwRSEBgNAhgOAgJHEAYThX4krXh/MxoCiimBDiqMMRp5gQeBRAOBNoFmhDQKgyKCXgSNc4MDhw9FgQCXG4JGlxUdj0IDjCctpnGFfwQugVhNLgqDJ1AYnH83MIEGAQGNJl8BAQ X-IronPort-AV: E=Sophos;i="5.72,326,1580745600"; d="scan'208";a="238809243" Received: from unknown (HELO mickey.themaw.net) ([118.209.166.232]) by icp-osb-irony-out4.iinet.net.au with ESMTP; 31 Mar 2020 08:54:31 +0800 Subject: [PATCH v2 4/4] autofs: add comment about autofs_mountpoint_changed() From: Ian Kent To: Al Viro Cc: autofs mailing list , linux-fsdevel , Kernel Mailing List Date: Tue, 31 Mar 2020 08:54:31 +0800 Message-ID: <158561607160.23197.3228166849408166685.stgit@mickey.themaw.net> In-Reply-To: <158561511964.23197.716188410829525903.stgit@mickey.themaw.net> References: <158561511964.23197.716188410829525903.stgit@mickey.themaw.net> User-Agent: StGit/unknown-version MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org The function autofs_mountpoint_changed() is unusual, add a comment about two cases for which it is used. Signed-off-by: Ian Kent --- fs/autofs/root.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/fs/autofs/root.c b/fs/autofs/root.c index b3f748e4df08..5efb7fa1ce2b 100644 --- a/fs/autofs/root.c +++ b/fs/autofs/root.c @@ -280,9 +280,24 @@ static struct dentry *autofs_mountpoint_changed(struct path *path) struct dentry *dentry = path->dentry; struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb); - /* - * If this is an indirect mount the dentry could have gone away - * as a result of an expire and a new one created. + /* If this is an indirect mount the dentry could have gone away + * and a new one created. + * + * This is unusual and I can't remember the case for which it + * was originally added now. But an example of how this can + * happen is an autofs indirect mount that has the "browse" + * option set and also has the "symlink" option in the autofs + * map entry. In this case the daemon will remove the browse + * directory and create a symlink as the mount (pointing to a + * local path) leaving the struct path stale. + * + * Another not so obvious case is when a mount in an autofs + * indirect mount that uses the "nobrowse" option is being + * expired and the mount has been umounted but the mount point + * directory remains when a stat family system call is made. + * In this case the mount point is removed (by the daemon) and + * a new mount triggered leading to a stale dentry in the struct + * path of the waiting process. */ if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) { struct dentry *parent = dentry->d_parent;