* autofs multi-map regression
@ 2017-06-16 10:14 Dick Streefland
2017-06-16 17:03 ` Eric W. Biederman
2017-06-16 20:57 ` Eric W. Biederman
0 siblings, 2 replies; 6+ messages in thread
From: Dick Streefland @ 2017-06-16 10:14 UTC (permalink / raw)
To: linux-kernel; +Cc: Eric W. Biederman
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 <ebiederm@xmission.com>
Date: Fri Jan 20 18:28:35 2017 +1300
mnt: Tuck mounts under others instead of creating shadow/side mounts.
--
Dick
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: autofs multi-map regression 2017-06-16 10:14 autofs multi-map regression Dick Streefland @ 2017-06-16 17:03 ` Eric W. Biederman 2017-06-16 20:39 ` Dick Streefland 2017-06-16 20:57 ` Eric W. Biederman 1 sibling, 1 reply; 6+ messages in thread From: Eric W. Biederman @ 2017-06-16 17:03 UTC (permalink / raw) To: Dick Streefland; +Cc: linux-kernel Dick Streefland <dick@streefland.net> 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 <ebiederm@xmission.com> > Date: Fri Jan 20 18:28:35 2017 +1300 > > mnt: Tuck mounts under others instead of creating shadow/side mounts. 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? Eric ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: autofs multi-map regression 2017-06-16 17:03 ` Eric W. Biederman @ 2017-06-16 20:39 ` Dick Streefland 2017-06-16 21:08 ` Eric W. Biederman 0 siblings, 1 reply; 6+ messages in thread From: Dick Streefland @ 2017-06-16 20:39 UTC (permalink / raw) To: Eric W. Biederman; +Cc: linux-kernel 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: autofs multi-map regression 2017-06-16 20:39 ` Dick Streefland @ 2017-06-16 21:08 ` Eric W. Biederman 0 siblings, 0 replies; 6+ messages in thread From: Eric W. Biederman @ 2017-06-16 21:08 UTC (permalink / raw) To: Dick Streefland; +Cc: linux-kernel Dick Streefland <dick@streefland.net> writes: > 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? Please. > 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: Thank you. I am definitely out of my depth on the autofs portion of this. As things are working with 4.11 and failing with my test of 4.4 with a much older kernel. I will leave this with you and the ubuntu folks to sort out. Good Luck, Eric > 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: autofs multi-map regression 2017-06-16 10:14 autofs multi-map regression Dick Streefland 2017-06-16 17:03 ` Eric W. Biederman @ 2017-06-16 20:57 ` Eric W. Biederman 2017-06-16 21:41 ` Dick Streefland 1 sibling, 1 reply; 6+ messages in thread From: Eric W. Biederman @ 2017-06-16 20:57 UTC (permalink / raw) To: Dick Streefland; +Cc: linux-kernel Dick Streefland <dick@streefland.net> 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 <ebiederm@xmission.com> > 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: autofs multi-map regression 2017-06-16 20:57 ` Eric W. Biederman @ 2017-06-16 21:41 ` Dick Streefland 0 siblings, 0 replies; 6+ messages in thread From: Dick Streefland @ 2017-06-16 21:41 UTC (permalink / raw) To: Eric W. Biederman; +Cc: linux-kernel On Friday 2017-06-16 15:57, Eric W. Biederman wrote: | 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. I have a second partition mounted on /loc, that is the reason for the multi-map autofs setup. With a separate mount on /loc, you won't see the errors with the old kernel. Fact is that my setup worked for a long time, and that it stopped working after the backport of commit 1064f874 to the ubuntu 4.4 kernel. -- Dick ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-06-16 21:41 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-06-16 10:14 autofs multi-map regression Dick Streefland 2017-06-16 17:03 ` Eric W. Biederman 2017-06-16 20:39 ` Dick Streefland 2017-06-16 21:08 ` Eric W. Biederman 2017-06-16 20:57 ` Eric W. Biederman 2017-06-16 21:41 ` Dick Streefland
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