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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 3B6BAC43467 for ; Thu, 8 Oct 2020 20:03:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6CF022226 for ; Thu, 8 Oct 2020 20:03:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729822AbgJHUDh (ORCPT ); Thu, 8 Oct 2020 16:03:37 -0400 Received: from sandeen.net ([63.231.237.45]:47186 "EHLO sandeen.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729877AbgJHUDh (ORCPT ); Thu, 8 Oct 2020 16:03:37 -0400 Received: from liberator.sandeen.net (liberator.sandeen.net [10.0.0.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by sandeen.net (Postfix) with ESMTPSA id D720F48C706; Thu, 8 Oct 2020 15:02:34 -0500 (CDT) To: Ian Kent , xfs References: <160212194125.16851.17467120219710843339.stgit@mickey.themaw.net> From: Eric Sandeen Subject: Re: [PATCH] xfsprogs: ignore autofs mount table entries Message-ID: Date: Thu, 8 Oct 2020 15:03:35 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <160212194125.16851.17467120219710843339.stgit@mickey.themaw.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 10/7/20 8:52 PM, Ian Kent wrote: > Some of the xfsprogs utilities read the mount table via. getmntent(3). > > The mount table may contain (almost always these days since /etc/mtab is > symlinked to /proc/self/mounts) autofs mount entries. During processing > of the mount table entries statfs(2) can be called on mount point paths > which will trigger an automount if those entries are direct or offset > autofs mount triggers (indirect autofs mounts aren't affected). > > This can be a problem when there are a lot of autofs direct or offset > mounts because real mounts will be triggered when statfs(2) is called. > This can be particularly bad if the triggered mounts are NFS mounts and > the server is unavailable leading to lengthy boot times or worse. > > Simply ignoring autofs mount entries during getmentent(3) traversals > avoids the statfs() call that triggers these mounts. If there are > automounted mounts (real mounts) at the time of reading the mount table > these will still be seen in the list so they will be included if that > actually matters to the reader. > > Recent glibc getmntent(3) can ignore autofs mounts but that requires the > autofs user to configure autofs to use the "ignore" pseudo mount option > for autofs mounts. But this isn't yet the autofs default (to prevent > unexpected side effects) so that can't be used. > > The autofs direct and offset automount triggers are pseudo file system > mounts and are more or less useless in terms on file system information > so excluding them doesn't sacrifice useful file system information > either. > > Consequently excluding autofs mounts shouldn't have any adverse side > effects. (usually this'd go below the "---") > Changes since v1: > - drop hunk from fsr/xfs_fsr.c. > > Signed-off-by: Ian Kent > --- > libfrog/linux.c | 2 ++ > libfrog/paths.c | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/libfrog/linux.c b/libfrog/linux.c > index 40a839d1..a45d99ab 100644 > --- a/libfrog/linux.c > +++ b/libfrog/linux.c > @@ -73,6 +73,8 @@ platform_check_mount(char *name, char *block, struct stat *s, int flags) > * servers. So first, a simple check: does the "dev" start with "/" ? > */ > while ((mnt = getmntent(f)) != NULL) { > + if (!strcmp(mnt->mnt_type, "autofs")) > + continue; I may change the order of this test and the next, just so it continues to align with the comment above. Shouldn't make any difference, right? Otherwise: Reviewed-by: Eric Sandeen > if (mnt->mnt_fsname[0] != '/') > continue; > if (stat(mnt->mnt_dir, &mst) < 0) > diff --git a/libfrog/paths.c b/libfrog/paths.c > index 32737223..d6793764 100644 > --- a/libfrog/paths.c > +++ b/libfrog/paths.c > @@ -389,6 +389,8 @@ fs_table_initialise_mounts( > return errno; > > while ((mnt = getmntent(mtp)) != NULL) { > + if (!strcmp(mnt->mnt_type, "autofs")) > + continue; > if (!realpath(mnt->mnt_dir, rmnt_dir)) > continue; > if (!realpath(mnt->mnt_fsname, rmnt_fsname)) > >