We are using automounter to mount some of our lustre filesystems on workernodes around the cluster.
These filesystems get unmounted after a long period of inactivity.

The problem i'd like to point is not frequent but may affect other users as well.
In some cases, when fs gets unmounted, the related entry is not removed from /etc/mtab file.
This leads to the situation when automounter is unable to mount lustre again.

Part of strace log from automount daemon:

...
[pid 19154] execve("/sbin/mount.lustre", ["/sbin/mount.lustre", "10.8.1.101:/scratch", "/mnt/auto/scratch-lustre", "-f", "-o", "rw,nosuid,nodev,localflock"], [/* 14 vars */]) = 0

...
[pid 19154] write(2, "mount.lustre: according to /etc/mtab 10.8.1.101:/scratch is already mounted on /mnt/auto/scratch-lustre\n", 104) = 104
...

To make mounting possible again, the related entry needs to be removed from /etc/mtab
I am not sure which part of the lustre-automount pair is mis-behaving here.
Is it automounter not removing the entry from /etc/mtab or mount.lustre ifself not checking
mount status in /proc/mounts?

More details:

[root@n2-1-1 ~]# grep -e lustre /etc/mtab
10.8.1.101:/scratch /mnt/auto/scratch-lustre lustre rw,nosuid,nodev,localflock 0 0
10.8.1.101:/storage /mnt/auto/storage-lustre lustre rw,nosuid,nodev,localflock 0 0
172.16.193.1@o2ib:/scratch /mnt/lustre/scratch lustre rw,nosuid,nodev,user_xattr,flock,acl,user_xattr,flock,acl 0 0

[root@n2-1-1 ~]# grep -e lustre /proc/mounts
10.8.1.101@tcp:/storage /mnt/auto/storage-lustre lustre rw,nosuid,nodev,localflock,acl 0 0
172.16.193.1@o2ib:/scratch /mnt/lustre/scratch lustre rw,nosuid,nodev,flock,acl 0 0

Best Regards
–
Lukasz Flis
ACC Cyfronet