[Samba] Large Delays in Samba Responses

[Matthew Jurgens]

 From time to time I get applications that use data on a Samba share 
locking up for long periods. Sometimes minutes.

I am using a Windows 10 client and Samba 4.12.5 on Fedora 32

smb.conf is pretty simple:

/[global]//
//   log file = /var/log/samba/%m.log//
//   writeable = yes//
//   workgroup = HOME//
//   hosts allow = 192.168.2.0/24 //
//   security = user//
//   passdb backend = tdbsam//
//   unix extensions = no//
//   load printers = no//
//   wide links = yes//
//   # trying disabling oplocks to see if that stops my hanging/delay 
problems//
//   oplocks = no//
//   socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=65536 
SO_SNDBUF=65536 SO_KEEPALIVE//
//
//   # needed for DDWRT routers//
//   ntlm auth = yes/

with shares like:

/[minecraft]//
//        path = /opt/msm//
//        create mask = 0765//
//        comment = Minecraft/


Changing oplocks did not help.

I've done some packet captures and they all look similar to this one:

https://www.edcint.co.nz/tmp/samba_ss01.jpg

Here you can see long delays where nothing is happening on the network, 
and the server is not resource constrained. While this is happening 
applications that are trying to use files on the share lock up. In the 
screenshot shown, there was some operations on an "opencv" file which 
was not even open or being touched by the application that was hanging. 
In fact, it would have been days ago since I last used the file in a 
different application.

smbstatus at the time did not list this file at all.

I had this problem years ago and it just disappeared and it was fine for 
years, now it is back and don't know what it is.

Any ideas? Any troubleshooting steps I can take?



The raw packet capture is available here, if needed:

https://www.edcint.co.nz/tmp/win0b.snoop