[systemd-devel] Possible race condition with LVM activation during boot

[suscricions at gmail.com]

El Thu, 07 Feb 2019 22:51:17 +0100
Martin Wilck <mwilck at suse.de> escribió:

> On Thu, 2019-02-07 at 19:13 +0100, suscricions at gmail.com wrote:
> > El Thu, 7 Feb 2019 11:18:40 +0100
> > 
> > There's been a reply in Arch Linux forums and at least I can apply
> > some
> > contingency measures. If it happens again I will provide more info
> > following your advice.  
> 
> The log shows clearly that the device was available first:
> 
> feb 06 12:07:09 systemd[1]: Starting File System Check
> on /dev/disk/by-uuid/cabdab31-983b-401f-be30-dda0ae462080... feb 06
> 12:07:09 systemd-fsck[520]: multimedia: limpio, 1051/953984 ficheros,
> 193506294/244189184 bloques feb 06 12:07:09 systemd[1]: Started File
> System Check
> on /dev/disk/by-uuid/cabdab31-983b-401f-be30-dda0ae462080.
> 
> That wouldn't be possible without the device being visible to the
> system. Shortly after you get
> 
> feb 06 12:07:09 mount[544]: mount: /mnt/multimedia: el dispositivo
> especial /dev/disk/by-uuid/cabdab31-983b-401f-be30-dda0ae462080 no
> existe.
> 
> ... So the device that had already been visible must have disappeared
> temporarily. After the mount failure, we see messages about the LV
> becoming active:
> 
> [...]
> feb 06 12:07:09 lvm[483]:   1 logical volume(s) in volume group
> "storage" now active [...]
> feb 06 12:07:09 lvm[494]:   1 logical volume(s) in volume group
> "storage" now active
> 
> There are two "lvm pvscan" processes (483 and 494) that may be
> interfering with each other and/or with the "mount" process. These
> processes are running on 8:17 (/dev/sdb1) and 254:1. I couldn't
> figure out from your logs what this latter device might be. 
> 
> Wild guess: the pvscan processes working on the VG while it's already
> visible are causing the device to get offline for a short time span,
> and if the mount is attempted in that time window, the error occurs.
> 
> There's another lvm process (340) started earlier by the lvm2-monitor
> unit ("Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or
> progress polling."). Immediately after termination of this process,
> the device seems to be detected by systemd and the above fsck/mount
> sequence begins, while the pvscan processes are still running. "lvm2-
> monitor.service" runs "vgchange --monitor y". It almost looks as if
> this had caused the devices to be visible by systemd, but that would
> be wrong AFAICT.
> 
> Can you reproduce this with "udev.log-priority=debug"?
> 
> Regards,
> Martin
> 
> 
> 

Hi Martin,

Do you want me to send the log of a clean boot with udev priority in
debug? I've tried to paste it on termbin.com but it's too big. When
gzipped it's around 140 KB. Maybe I can just paste it as binary hehe.

You tell me.


Best.