Bug#827077: linux: autofs mounts hang after real mount is unmounted

[Felipe Sateler]

Control: forcemerge 826512 -1

On 16 June 2016 at 10:46, Julian Andres Klode <jak at debian.org> wrote:
>> On Sun, Jun 12, 2016 at 01:31:34AM +0200, Julian Andres Klode wrote:
>> > Package: src:linux
>> > Version: 4.6.1-1
>> > Severity: normal
>> >
>> > Hi, my system mounts /boot/efi using autofs, so it is automatically unmounted
>> > after not being used (for safety reasons). The settings are (from /proc/mounts):
>> >
>> > systemd-1 /boot/efi autofs rw,relatime,fd=29,pgrp=1,timeout=10,minproto=5,maxproto=5,direct,pipe_ino=10578 0 0
>> > /dev/sdb1 /boot/efi vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro 0 0
>> >
>> > At first, accessing /boot works normally. But once /boot/efi (vfat) is unmounted, the automount
>> > mount causes processes accessing it to hang (see the dmesg below). Even manually mounting the vfat
>> > partition does not unhang those processes and new processes still hang.
>> >
>> > This affects ls --color /boot for example, which just hangs when doing lstat("/boot/efi").
>> >
>> > This works successfully in 4.5.5-1, and I have not seen the bug in 4.6.0-{rc7,trunk} (but I might
>> > not have looked at /boot in those versions).
>>
>> Hmm, I just reproduced it in 4.5.5-1. Unmounting the autofs thing makes things work
>> again. I wonder what's really causing this.
>>
>> It definitely used to work at some point. Maybe it's actually a systemd issue? I'm not
>> exactly sure how autofs works and who actually mounts the vfat and hangs doing so
>> (kernel or systemd?).
>
> It's a bug in systemd 230. Arch applies the following commit to fix it:
>
>   # automount: handle expire_tokens when the mount unit changes its state (#3434)
>   0a62f81045dd810c8f1223cccbac4d706ea2cb45

As discussed on IRC, it appears this is the same as #826512. Merging.

-- 

Saludos,
Felipe Sateler