[Dnsmasq-discuss] [PATCH] dnsmasq: failed to create inotify for /etc/resolv.conf: No space left on device

[Petr Menšík]

Hello!

I have recently started to have issues when starting libvirt, which 
starts dnsmasq for DHCP and local machine DNS.

I have started seeing inotify sockets failures in multiple packages. But 
the thing is, I cannot start libvirt network now. I think inotify socket 
should not usually be cause of fatal error.

sudo virsh net-start default ends always with this failure. It usually 
helps to reboot the machine. I am not sure how to identify inotify usage 
on my machine.

Strange is this seems to be problem only of root user.

$ sudo inotifywatch /etc/resolv.conf
Establishing watches...
Failed to watch /etc/resolv.conf; upper limit on inotify watches reached!

$ inotifywatch /etc/resolv.conf
Establishing watches...
Finished establishing watches, now collecting statistics.

Strange is number of user watches should be somehow high:

$ cat /proc/sys/fs/inotify/max_user_watches
511013

So I started thinking, should be a failure to initialize inotify socket 
a fatal error? It seems to me warning would be all right.

dnsmasq supports running even without inotify support. I have created a 
modification to run even in that case, only emit warning. I think 
failure to observe resolv.conf changes should not be a fatal error, 
unless requested somehow more explicitly.

In attached change, I retry inotify creation with dropped privileges. It 
might help in my case and even for others. First time it fails only 
silently, because logging is not yet prepared. Only second time it also 
logs warnings.

Minor change is making more obvious difference between main inotify 
socket and inotify watch creation error.

Regards,
Petr

-- 
Petr Menšík
Senior Software Engineer, RHEL
Red Hat, https://www.redhat.com/
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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