samba - Jan 2023 - oplocks, kernel oplocks, kernel share modes, .. - how it all works?

On Tue, Jan 24, 2023 at 09:51:01PM +0000, Rowland Penny via samba
wrote:
>
>So, are we back to what I said originally ? that it is a BAD idea to 
>locally modify anything in a Samba share and it should only be 
>modified by Samba or from a SMB client ?
It is... inadvisable to do local modifications. Having said that
the "kernel oplocks" parameter (when set in the [global] section only)
on Linux will allow this to be done safely w.r.t. file-level caching
at the cost of falling back to the old oplock model rather than the
modern SMB2 leases.

It will depend on applications being used that understand each
others locking and simultaneous open semantics in order to be
safe though.

So yeah. Advanced option, only use if you *really* know what
you're doing and understand the risks involved.

I think Michael is asking the right questions to get to something
that will work for him. And after all, the purpose of this
list is to help people to use Samba to do really dangerous
things :-) :-) :-).

On 24/01/2023 21:57, Jeremy Allison wrote:
> On Tue, Jan 24, 2023 at 09:51:01PM +0000, Rowland Penny via samba wrote:
>>
>> So, are we back to what I said originally ? that it is a BAD idea to 
>> locally modify anything in a Samba share and it should only be 
>> modified by Samba or from a SMB client ?
> 
> It is... inadvisable to do local modifications. Having said that
> the "kernel oplocks" parameter (when set in the [global] section
only)
> on Linux will allow this to be done safely w.r.t. file-level caching
> at the cost of falling back to the old oplock model rather than the
> modern SMB2 leases.
> 
> It will depend on applications being used that understand each
> others locking and simultaneous open semantics in order to be
> safe though.
> 
> So yeah. Advanced option, only use if you *really* know what
> you're doing and understand the risks involved.
> 
> I think Michael is asking the right questions to get to something
> that will work for him. And after all, the purpose of this
> list is to help people to use Samba to do really dangerous
> things :-) :-) :-).
Whilst I can fully understand what you are trying to say, I still think 
that it is a bad idea to locally modify files on a Samba share. I also 
think that what Michael requires is a good thing, it just isn't really 
possible at this time, perhaps Samba could be enhanced to do it, so it 
might be an idea to open a bug report so it doesn't get forgotten. The 
major problem will be in getting external programs to work with the 
Samba files and that will not be easy.

Rowland