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

[Jeremy Allison]

On Tue, Jan 24, 2023 at 08:29:17PM +0300, Michael Tokarev via samba wrote:
>24.01.2023 20:22, Ralph Boehme via samba wrote:
>>What Samba version is this? This:
>>
>>>LEASE()
>>
>>... looks broken: the handle oplock/lease state claims to be a 
>>lease, which means the client didn't request an oplock but a lease 
>>which should not have happened in the first place, because the 
>>global leases capabiltiy is not signaled by the server when kernel 
>>oplocks are enabled.
>>
>>I assume this is 4.17? That saw substantial changes in the core open 
>>handling, I'm worried that some of the subtle oplock/lease handling 
>>was broken by those changes.
>
>Yes this is 4.17[.4], the current stable (debian build of it).
>
>I assumed LEASE() is okay because it is in fact SMB1 oplock, not a lease,
>again as per your prior explanations.  As I wrote before, this LEASE()
>appeared here (instead of LEASE(RH) etc) when I enabled kernel oplocks
>(for this share anyway).

What are the settings in your smb.conf ?

The 4.17 code does (in source3/smbd/open.c):

2727         if (oplock_request == LEASE_OPLOCK) {
2728                 if (lease == NULL) {
2729                         /*
2730                          * The SMB2 layer should have checked this
2731                          */
2732                         return NT_STATUS_INTERNAL_ERROR;
2733                 }
2734 
2735                 granted = lease->lease_state;
2736 
2737                 if (lp_kernel_oplocks(SNUM(fsp->conn))) {
2738                         DEBUG(10, ("No lease granted because kernel oplocks are enabled\n"));
2739                         granted = SMB2_LEASE_NONE;
2740                 }

so you end up with oplock_request == LEASE_OPLOCK, granted=SMB2_LEASE_NONE.

then further down is:

2781         if (oplock_request == LEASE_OPLOCK) {
2782                 if (state.got_oplock) {
2783                         granted &= ~SMB2_LEASE_HANDLE;
2784                 }
2785 
2786                 fsp->oplock_type = LEASE_OPLOCK;
2787 
2788                 status = grant_fsp_lease(fsp, lck, lease, granted);
2789                 if (!NT_STATUS_IS_OK(status)) {
2790                         return status;
2791 
2792                 }
2793 
2794                 DBG_DEBUG("lease_state=%d\n", fsp->lease->lease.lease_state);
2795         } else {

which means you end up with LEASE_OPLOCK, granted=SMB2_LEASE_NONE
which is what you see with smbstatus.

If you turn on kernel oplocks = yes, I think you must also
set smb2 leases = no in order for this to work.