From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751812AbdFPVFD (ORCPT ); Fri, 16 Jun 2017 17:05:03 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:44980 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854AbdFPVFC (ORCPT ); Fri, 16 Jun 2017 17:05:02 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Dick Streefland Cc: linux-kernel@vger.kernel.org References: <20170616101440.GA1480@neos> Date: Fri, 16 Jun 2017 15:57:58 -0500 In-Reply-To: <20170616101440.GA1480@neos> (Dick Streefland's message of "Fri, 16 Jun 2017 12:14:41 +0200") Message-ID: <87r2yjr6p5.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1dLyQI-0005Zh-NM;;;mid=<87r2yjr6p5.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=67.3.213.87;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+XkxAtLXKo3UCkd6NqWEVUgxdow/fvvJI= X-SA-Exim-Connect-IP: 67.3.213.87 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4995] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.1 XMSolicitRefs_0 Weightloss drug * 0.5 XM_Body_Dirty_Words Contains a dirty word X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Dick Streefland X-Spam-Relay-Country: X-Spam-Timing: total 5733 ms - load_scoreonly_sql: 0.03 (0.0%), signal_user_changed: 2.4 (0.0%), b_tie_ro: 1.70 (0.0%), parse: 0.71 (0.0%), extract_message_metadata: 17 (0.3%), get_uri_detail_list: 1.73 (0.0%), tests_pri_-1000: 9 (0.1%), tests_pri_-950: 1.11 (0.0%), tests_pri_-900: 0.96 (0.0%), tests_pri_-400: 18 (0.3%), check_bayes: 17 (0.3%), b_tokenize: 6 (0.1%), b_tok_get_all: 5 (0.1%), b_comp_prob: 1.84 (0.0%), b_tok_touch_all: 2.4 (0.0%), b_finish: 0.58 (0.0%), tests_pri_0: 166 (2.9%), check_dkim_signature: 0.45 (0.0%), check_dkim_adsp: 2.8 (0.0%), tests_pri_500: 5515 (96.2%), poll_dns_idle: 5508 (96.1%), rewrite_mail: 0.00 (0.0%) Subject: Re: autofs multi-map regression X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dick Streefland writes: > After a recent upgrade of a Ubuntu xenial machine, a particular > autofs multi-map mount setup stopped working. A simplified example is: > > :::::::::::::: > auto.master > :::::::::::::: > /net /etc/auto.net > :::::::::::::: > auto.net > :::::::::::::: > localhost / :/ /loc :/loc > > Accessing /net/localhost/loc should trigger two nested bind mounts on > /net/localhost and /net/localhost/loc, but with the new kernel, it fails > with ELOOP: > > $ ls /net/localhost/loc > ls: cannot open directory '/net/localhost/loc': Too many levels of symbolic links > > The problem is related to the upgrade of the Ubuntu xenial kernel from > 4.4.0-38.57 to 4.4.0-78.99. I bisected the regression to commit > 731ac92843877f3633325203abc942193c1e9001, which is a Ubuntu backport > of this upstream kernel commit: > > commit 1064f874abc0d05eeed8993815f584d847b72486 > Author: Eric W. Biederman > Date: Fri Jan 20 18:28:35 2017 +1300 > > mnt: Tuck mounts under others instead of creating shadow/side mounts. I don't believe this is a kernel change. I dug up an old VM and I was able to reproduce this issue simply by installing autofs, and your auto.master and auto.net files. # uname -a Linux ubuntu-16 4.4.0-24-generic #43-Ubuntu SMP Wed Jun 8 19:27:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux # ls /net/ localhost # ls /net/localhost/loc ls: cannot open directory '/net/localhost/loc': Too many levels of symbolic links # ls /loc ls: cannot open directory '/loc/': Too many levels of symbolic links I suspect there is configuration somewhere in your autofs configuration. I don't speak autofs well enough to debug the issue at this point. But I can conclusively say it was not the kernel commit you pointed at, as I see the issue you are reporting and I don't have that commit in the kernel under test. Eric