samba - May 2019 - Weird Samba/CIFS behavior: client hangs

Hi there!

I have a very weird behavior in samba. I have been using a samba server
for sharing a folder to a cifs mount client for many years. Since last
update, everything still works fine, but when i open a photo subfolder
with a specific software (gwenview) and try to load thumbnails, the
whole mount stops responding.

On the client, i have the "server not responding after 120 seconds"
message. On the server, i can't see anything weird on the logs.

Restarting the server solves brings the client back to life (after a few
seconds), then it hangs again after loading 15-20 thumbs.

I have checked disks and network and found no problems. Access to files
is very fast, as long as i access: by example, i can md5sum all the
files in that folder and get a very good throughput. The problem seems
to appear only when that software is loading thumbs.

My mount in fstab is:
//server/Dati /mnt/dati cifs
rw,nouser,auto,credentials=/etc/samba/credentials,iocharset=utf8,soft,_netdev,comment=systemd.automount,user_xattr,file_mode=0600,dir_mode=0700,vers=1.0
0 0

Maybe something related to opening many files at once? Any ideas?

Thanks

Gabriele

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