linux-kernel - Re: autofs multi-map regression

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Date:   Fri, 16 Jun 2017 22:39:52 +0200
From:   Dick Streefland <dick@...eefland.net>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: autofs multi-map regression

On Friday 2017-06-16 12:03, Eric W. Biederman wrote:
| Interesting...
| 
| Can you test this on a stock 4.11 kernel?
| 
| I definitely need a little bit more information to solve this.  That
| commit did not add any new error condidtions so I need to understand
| what state you are getting yourself into that is affected by this
| commit.
| 
| Is there a chance you can post /proc/self/mountinfo from when this is
| happening?

I've installed the mainline 4.11 kernel from:

  http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.11/

and this kernel works correctly!

So either this issue was fixed in the meantime, or it is something
specific to the Ubuntu kernel. I guess I should file a bug report
with Ubuntu then?

I've also looked at /proc/self/mountinfo before and directly after the
mount attempt. Here are the ext4 and autofs entries for the failing 4.4
kernel:

before:
23 0 8:2 / / rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
41 19 0:34 / /proc/sys/fs/binfmt_misc rw,relatime shared:24 - autofs systemd-1 rw,fd=34,pgrp=1,timeout=0,minproto=5,maxproto=5,direct
46 23 8:4 / /loc rw,nosuid,nodev,noatime shared:30 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl
202 23 0:44 / /net rw,relatime shared:160 - autofs /etc/auto.net rw,fd=6,pgrp=1724,timeout=120,minproto=5,maxproto=5,indirect

after:
23 0 8:2 / / rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
41 19 0:34 / /proc/sys/fs/binfmt_misc rw,relatime shared:24 - autofs systemd-1 rw,fd=34,pgrp=1,timeout=0,minproto=5,maxproto=5,direct
46 162 8:4 / /loc rw,nosuid,nodev,noatime shared:30 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl
202 23 0:44 / /net rw,relatime shared:160 - autofs /etc/auto.net rw,fd=6,pgrp=1724,timeout=120,minproto=5,maxproto=5,indirect
157 202 8:2 / /net/localhost rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
161 157 0:47 / /net/localhost/loc rw,relatime shared:119 - autofs /etc/auto.net rw,fd=6,pgrp=1724,timeout=120,minproto=5,maxproto=5,offset
162 23 0:47 / /loc rw,relatime shared:119 - autofs /etc/auto.net rw,fd=6,pgrp=1724,timeout=120,minproto=5,maxproto=5,offset

And here the info for the working mainline 4.11 kernel:

before:
23 0 8:2 / / rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
74 19 0:36 / /proc/sys/fs/binfmt_misc rw,relatime shared:56 - autofs systemd-1 rw,fd=35,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=12754
45 23 8:4 / /loc rw,nosuid,nodev,noatime shared:28 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl
208 23 0:46 / /net rw,relatime shared:164 - autofs /etc/auto.net rw,fd=6,pgrp=1545,timeout=120,minproto=5,maxproto=5,indirect,pipe_ino=26555

after:
23 0 8:2 / / rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
74 19 0:36 / /proc/sys/fs/binfmt_misc rw,relatime shared:56 - autofs systemd-1 rw,fd=35,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=12754
45 175 8:4 / /loc rw,nosuid,nodev,noatime shared:28 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl
208 23 0:46 / /net rw,relatime shared:164 - autofs /etc/auto.net rw,fd=6,pgrp=1545,timeout=120,minproto=5,maxproto=5,indirect,pipe_ino=26555
162 208 8:2 / /net/localhost rw,relatime shared:1 - ext4 /dev/sda2 rw,errors=remount-ro,data=ordered
166 162 0:48 / /net/localhost/loc rw,relatime shared:122 - autofs /etc/auto.net rw,fd=6,pgrp=1545,timeout=120,minproto=5,maxproto=5,offset,pipe_ino=26555
167 23 0:48 / /loc rw,relatime shared:122 - autofs /etc/auto.net rw,fd=6,pgrp=1545,timeout=120,minproto=5,maxproto=5,offset,pipe_ino=26555
174 166 8:4 / /net/localhost/loc rw,nosuid,nodev,noatime shared:28 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl
175 167 8:4 / /loc rw,nosuid,nodev,noatime shared:28 - ext4 /dev/sda4 rw,block_validity,delalloc,barrier,user_xattr,acl

-- 
Dick