leases and F_NOTIFY in samba 3 & 4

[James Peach]

On Mon, 2006-04-10 at 15:17 -0500, Abhijith Das wrote:
> Hi List,
> 
> I understand that Samba uses F_SETLEASE, F_GETLEASE fcntls to implement 
> oplocks in linux. Atleast in Samba3.
> Does Samba4 also use linux kernel leases? How much of a performance 
> impact is it to run Samba with oplocks disabled?
> I'm about to implement lease support for GFS, but at the outset, there 
> seems to be a significant performance impact for the fs.

CXFS supports exclusive oplocks natively and I don't believe that the
implementation is especially expensive (except in the break case).
Originating on IRIX, it's a matter of stacking oplock-specific
behaviours at the head of the behaviour chain for a particular vnode.
It's terribly complex to debug the oplock break though.

Given the rate of change of the Samba 3 oplock implementation over the
last year or so, I'm not that sure that pushing it into the
kernel/cluster is a great idea.

-- 
James Peach | jpeach at samba.org