Re: Linux 4.0.6 breaks my disk/lvm/filesystem setup

[Christian Hesse]

Hello everybody,

I kind of nailed the issue. Adding CC to Greg for kdbus and to Herbert for
the bad commit. Details are below.

Christian Hesse <list@xxxxxxxx> on Tue, 2015/06/23 10:14:
> with Linux 4.0.5 everything was perfectly fine, Linux 4.0.6 breaks the setup
> on one of my systems: Only three of my logical volumes are available,
> systemd reports:
> 
> lvm2-pvscan@254:3.service: State 'stop-sigterm' timed out. Killing.
> 
> Followed by a lot of failed dependencies. The setup looks like this:
> 
> NAME                MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
> sda                   8:0    0 953,9G  0 disk  
> |-sda1                8:1    0     1M  0 part  
> |-sda2                8:2    0   256M  0 part  /boot/efi
> |-sda3                8:3    0   7,8G  0 part  
> | |-vg-iso          254:0    0     4G  0 lvm   /srv/iso
> | |-vg-persist      254:1    0     2G  0 lvm   /srv/iso/persist
> | `-vg-boot         254:2    0   128M  0 lvm   /boot
> |-sda4                8:4    0 913,9G  0 part  
> | `-cvg             254:3    0 913,9G  0 crypt 
> |   |-cvg-swap      254:4    0     4G  0 lvm   [SWAP]
> |   |-cvg-root      254:5    0    40G  0 lvm   /
> |   |-cvg-log       254:6    0     1G  0 lvm   /var/log
> |   |-cvg-home      254:7    0   500G  0 lvm   /home
> |   |-cvg-vbox_win7 254:8    0    32G  0 lvm   
> |   |-cvg-vbox_win8 254:9    0    32G  0 lvm   
> |   |-cvg-git       254:10   0    12G  0 lvm   /srv/git
> |   `-cvg-chroots   254:11   0    16G  0 lvm   /var/lib/archbuild
> `-sda5                8:5    0    32G  0 part
> 
> Another system is just fine, the only difference is a logical volume with
> btrfs (cvg-chroots). Possibly the btrfs fixes are involved?

I am running Linux 4.0.x with kdbus from Greg's char-misc tree kdbus branch
[0] merged, last commit is b69af624a0 ("kdbus: optimize if statements in
kdbus_conn_disconnect()"). Everything works fine with Linux 4.0.5 but breaks
with 4.0.6 on one of my systems.

I bisected the problem and found this to be the bad commit [1]:

  From cf8befcc1a5538b035d478424efcc2d50e66928e Mon Sep 17 00:00:00 2001
  From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
  Date: Sat, 16 May 2015 21:16:28 +0800
  Subject: netlink: Disable insertions/removals during rehash

  [ Upstream commit: Not applicable ]

  The current rhashtable rehash code is buggy and can't deal with
  parallel insertions/removals without corrupting the hash table.

  This patch disables it by partially reverting
  c5adde9468b0714a051eac7f9666f23eb10b61f7 ("netlink: eliminate
  nl_sk_hash_lock").

I can fix my system by booting with kdbus=0 to disable kdbus or by reverting
this single commit. Looks like anything deadlocks... Any idea?

[0] https://git.kernel.org/cgit/linux/kernel/git/gregkh/char-misc.git/?h=kdbus
[1]
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=cf8befcc
-- 
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