[DRBD-user] Blocked I/O on /dev/drbd0

Julien Escario escario at azylog.net
Fri Nov 3 11:38:00 CET 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hello,
This is not the first I'm seeing what is probably a bug in a older version.
Upgrade is on the way but I need to unblock situation.

Symptoms :
All lvm (I'm using thin-lvm backend) and drbd related commands are blocked on
opening /dev/drbd0 :
# strace lvdisplay
[....]
stat("/dev/drbd0", {st_mode=S_IFBLK|0660, st_rdev=makedev(147, 0), ...}) = 0
open("/dev/drbd0", O_RDONLY|O_DIRECT|O_NOATIME

Same with all drbdsetup and lvm commands.

drbdmanage fail with communication error with the drbdmanaged process :
# drbdmanage n

Error: Cannot connect to the drbdmanaged process using DBus
The DBus subsystem returned the following error description:
org.freedesktop.DBus.Error.TimedOut: Activation of org.drbd.drbdmanaged timed out

So, more investigation :
# ps aux | grep " D"
[snip containing all drbd and lvm related commands launched to debug]
root     27352  0.0  0.0      0     0 ?        D    Jun15   0:03 [drbd_r_.drbdctr]
root     27353  0.0  0.0      0     0 ?        D    Jun15   0:00 [drbd_r_.drbdctr]
root     29648  0.0  0.0 110012 14472 ?        D     2016  93:30 /usr/bin/python
/usr/bin/dbus-drbdmanaged-service


So, as for as I understand, drbdmanaged opened exclusively the device and
doesn't give it back.

Am I right ?

Is there a way to unblock this without rebooting the whole node ? I tried
drbdmanage shutdown -q.

Kill directly the process ? Is it safe ?

Best regards,
Julien Escario



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