[Samba] oplocks, kernel oplocks, kernel share modes, .. - how it all works?

[Rowland Penny]

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