[PATCH] Increase SMB/CIFS file attribute cache time

[Matt Corallo]

On 8/19/22 6:02 AM, Fiona Ebner wrote:
> Hi,
> 
> On 16.08.22 05:16, Matt Corallo wrote:
>> For those using SMB for long-distance remote backups, the default
>> cache setting of 1 second for file attributes causes the GUI
>> "backup" tabs to time-out long before they finishing loading.
> 
> I'm not saying increasing the timeout can't be worth it, but I haven't
> seen many reports about the default being too low. There is a patch in
> the works [0] allowing to set custom options in the storage
> configuration for CIFS which would allow changing the timeout only for
> setups that actually require it.
> 
> [0]: https://lists.proxmox.com/pipermail/pve-devel/2022-July/053645.html

Heh, I may simply be the only crazy person trying to use SMB to do backups with a 150ms RTT.

Its possible there's something about samba that's making the latency cause Proxmox to hang, but I 
combed through samba and mount options rather carefully and the only change which impacted my 
ability to list backups on Proxmox was this one.

If I understand the mount.cifs manpage correctly, this is only about caching attributes, so even if 
a file is removed on one host that will show up quickly, its only if one machine is editing 
permissions that it could cause issue (but I don't think proxmox cares about/touches the file 
permissions on backups, no?). I thus figured it was pretty safe, but certainly if there's no reason 
to support this, a custom mount options knob would solve the issue for me.

Thanks,
Matt