On Wed, Jun 30, 2021 at 01:41:32AM -0700, dai.ngo@xxxxxxxxxx wrote:
>
> On 6/29/21 6:35 PM, J. Bruce Fields wrote:
> >On Mon, Jun 28, 2021 at 09:40:56PM -0700, dai.ngo@xxxxxxxxxx wrote:
> >>On 6/28/21 4:39 PM, dai.ngo@xxxxxxxxxx wrote:
> >>>On 6/28/21 1:23 PM, J. Bruce Fields wrote:
> >>>>On Thu, Jun 03, 2021 at 02:14:38PM -0400, Dai Ngo wrote:
> >>>>>@@ -6875,7 +6947,12 @@ nfsd4_lock(struct svc_rqst *rqstp,
> >>>>>struct nfsd4_compound_state *cstate,
> >>>>> case -EAGAIN: /* conflock holds conflicting lock */
> >>>>> status = nfserr_denied;
> >>>>> dprintk("NFSD: nfsd4_lock: conflicting lock found!\n");
> >>>>>- nfs4_set_lock_denied(conflock, &lock->lk_denied);
> >>>>>+
> >>>>>+ /* try again if conflict with courtesy client */
> >>>>>+ if (nfs4_set_lock_denied(conflock, &lock->lk_denied)
> >>>>>== -EAGAIN && !retried) {
> >>>>>+ retried = true;
> >>>>>+ goto again;
> >>>>>+ }
> >>>>Ugh, apologies, this was my idea, but I just noticed it only
> >>>>handles conflicts
> >>>>from other NFSv4 clients. The conflicting lock could just as
> >>>>well come from
> >>>>NLM or a local process. So we need cooperation from the common
> >>>>locks.c code.
> >>>>
> >>>>I'm not sure what to suggest....
> >>One option is to use locks_copy_conflock/nfsd4_fl_get_owner to detect
> >>the lock being copied belongs to a courtesy client and schedule the
> >>laundromat to run to destroy the courtesy client. This option requires
> >>callers of vfs_lock_file to provide the 'conflock' argument.
> >I'm not sure I follow. What's the advantage of doing it this way?
>
> I'm not sure it's an advantage but I was trying to minimize changes to
> the fs code. The only change we need is to add the conflock argument
> to do_lock_file_wait to handle local lock conflicts.
Got it.
That's a clever but kind of unexpected use of lm_get_owner; I think it
could be confusing to a future reader. And I'd rather not require the
extra retry. A new lock callback is a complication, but at least it's
pretty obvious what it does.
> If you don't think we're going to get objection with the new callback,
> fl_expire_lock, then I will take that approach. We still need to add
> the conflock argument to do_lock_file_wait in this case.
Why is that?
--b.
