[Samba] fuser calls create zombie processes on samba file server

[Gérard GUEVEL]

Hello,

 

I want to relate a Samba client issue which could hide a Samba server issue.

 

For my own, three machines are involved :

A Samba version 4.18.6-Debian Active Directory DC server.

A Samba version 4.13.13-Debian Domain Member FILE server.

An Ubuntu 20.04.6 LTS BENCH server with a CIFS share mounted on FILE server.

 

A BENCH application run many threads which have to check the opened files
each

second using a python fuser call. After about 5 hours, the FILE server
claims that

too many files are opened and the max open files limit (16384) is reached.

The FILE server does not crash but remains exhausted to serve all other
clients.

 

We found that if a first fuser call is running while a second one is
launched then

the first opened process is never closed on the FILE server. So each second,

we create a zombie Samba process and reach the OS limit after about 5
heures.   

 

Our workaround is to flock (mutex) the fuser call to avoid server
conflicting calls.

I don’t understand why concurrent fuser calls can corrupt the server.

 

Thanks for any explaination.

Gerard GUEVEL