DBase File locking issues (PR#20441)

[Jeremy Allison]

tridge at linuxcare.com wrote:
> 
> > >   locking not supported? returning True
> >
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > This above is old crufty code that is no longer needed; it was
> > used for systems that didn't have fcntl locks. We now check
> > for these at compile time and refuse to run. I'm removing
> > this asap.
> 
> be careful. This code was for systems that support locks on some
> filesystems but not others. For example, many Linux systems don't
> support fcntl locks at all on NFS fileystems. If you compile on ext2
> then run Samba on NFS removing that code will cause Samba to fail
> completely. That is quite a common setup.

Hmmmm. The problem is that this code masks real problems with
locking. I can see your point though, but then allowing locking
to just completely fail on a filesystem is risking file corruption.
I suppose it's one of these things that has been there a while,
and we need to make a decision on backwards compatibility or
correctness.

> At the very least we would need to add docs advising users to use
> "locking = no" on filesystems that don't support fcntl locks, but I'd
> prefer to automate that with a runtime test.

That's going to be hard to do as we don't know if the
filesystem Samba is being configured on is NFS or not.

Jeremy.

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