On 06/27/2016 02:26 AM, Ian Kent wrote:
How is autofs configured.
If --disable-mount-locking is not used then any mount can block all other
mounts, if it is used then there can be mtab corruption if still using a text
based mtab.
I use --disable-mount-locking.
I always use --disable-mount-locking and nowadays the mtab is usually a symlink
into the proc file system so corruption isn't a problem.
/etc/mtab is actually not a symlink on my systems.
Anyway, I have more details for you as the issue appeared today and I
could investigate some more. This is on a server that only mounts one
single NFS server (http12), so the multi-servers blocking issue is
irrelevant here.
A few minutes before the "deadlock" occurred, /nfs/http12 was unmounted
by autofs, I assume because it was idle. I have TIMEOUT=600. That
explains why the issue appears much more frequently on a server which is
way less busy (and usually in the middle of the night): the NFS server
needs to be idle enough to be unmounted.
However, I still had many /home/userX mounted (by autofs), which point
to /nfs/http12/userX. Shouldn't autofs not unmount /nfs/http12 when at
least one /home/userX is mounted? To be clear, here's an extract from my
/proc/mounts BEFORE the NFS server is unmounted by autofs:
http12:/ /nfs/http12 nfs4
rw,nosuid,noatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,soft,proto=tcp6,timeo=1000,retrans=2,sec=sys,clientaddr=2a00:42:1:50:1::1,local_lock=none,addr=2a00:42:1:20:1::1
0
0
http12://user1 /home/user1 nfs4
rw,nosuid,noatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,soft,proto=tcp6,timeo=1000,retrans=2,sec=sys,clientaddr=2a00:42:1:50:1::1,local_lock=none,addr=2a00:42:1:20:
1::1 0 0
http12://user2 /home/user2 nfs4
rw,nosuid,noatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,soft,proto=tcp6,timeo=1000,retrans=2,sec=sys,clientaddr=2a00:42:1:50:1::1,local_lock=none,addr=2a00:42:1:2
0:1::1 0 0
Also, I couldn't find any blocked mount process that would explain the
"deadlock". I had a 'ps aux|grep mount' done every 10 seconds:
Mon Jun 27 05:00:00 CEST 2016
root 3437 0.0 0.0 218676 5500 ? Ssl Jun24 0:26
/usr/sbin/automount --pid-file /var/run/autofs.pid
Mon Jun 27 05:00:10 CEST 2016
root 3437 0.0 0.0 218676 5500 ? Ssl Jun24 0:27
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618146 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618214 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618215 0.0 0.0 0 0 ? Z 05:00 0:00
[umount] <defunct>
root 2618224 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618227 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618230 0.0 0.0 0 0 ? Z 05:00 0:00
[umount] <defunct>
root 2618240 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618248 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618250 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618252 0.1 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
Mon Jun 27 05:00:20 CEST 2016
root 3437 0.0 0.0 218676 5500 ? Ssl Jun24 0:27
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618146 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618214 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618224 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618227 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618240 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618248 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618250 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618252 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618701 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
root 2618702 0.0 0.0 218676 2168 ? S 05:00 0:00
/usr/sbin/automount --pid-file /var/run/autofs.pid
And it remained in that state afterwards. I don't know if the defunct
umount are suspicious, I guess not.
One last thing: a manual umount of /home/userY was done by a script at
6:26 (/home/userY was NOT mounted though), and it remained blocked. I'm
not sure if it's a consequence of autofs being blocked or something else.
--
Cyril B.
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