Re: [PATCH v6 2/9] nfsd: fully unhash delegations when revoking them

[Jeff Layton <jeff.layton@primarydata.com>]

On Tue, 29 Jul 2014 10:53:31 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Fri, Jul 25, 2014 at 07:34:20AM -0400, Jeff Layton wrote:
> > @@ -698,11 +699,10 @@ static void revoke_delegation(struct nfs4_delegation *dp)
> >  	struct nfs4_client *clp = dp->dl_stid.sc_client;
> >  
> >  	if (clp->cl_minorversion == 0)
> > -		destroy_delegation(dp);
> > +		destroy_revoked_delegation(dp);
> 
> I don't understand this one--in the NFSv4.0 case, when is the delegation
> unhashed?
> 
> (And, apologies if that's a repeat question.  I remember wondering about
> this before but can't find mail in the archives....)
> 
> --b.
> 

It's unhashed by the laundromat (or the fault injection code). The
deltas that change that are later in this patch, but it doesn't have
much context so it's a little tricky to spot. Here's the relevant code
chunk from nfs4_laundromat:

---------------[snip]-----------------
        spin_lock(&state_lock);
        list_for_each_safe(pos, next, &nn->del_recall_lru) {
                dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
                if (net_generic(dp->dl_stid.sc_client->net, nfsd_net_id) != nn)
                        continue;
                if (time_after((unsigned long)dp->dl_time, (unsigned long)cutoff)) {
                        t = dp->dl_time - cutoff;
                        new_timeo = min(new_timeo, t);
                        break;
                }
                unhash_delegation_locked(dp);
                list_add(&dp->dl_recall_lru, &reaplist);
        }
        spin_unlock(&state_lock);
        list_for_each_safe(pos, next, &reaplist) {
                dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
                revoke_delegation(dp);
        }
---------------[snip]-----------------

...so the laundromat walks the nn->del_recall_lru list, unhashes any
delegation that has expired and gathers them up onto the list. Then, it
calls revoke_delegation on each outside of the lock.

As a side note, that net_generic comparison there looks bogus to me.
How could you ever end up with an entry from a different namespace on
this list? I left it in for now since it didn't seem relevant (or
terribly expensive), but I suspect that it can be removed (or turned
into a WARN or something).

> >  	else {
> > -		unhash_delegation(dp);
> >  		dp->dl_stid.sc_type = NFS4_REVOKED_DELEG_STID;
> > -		list_add(&dp->dl_recall_lru, &clp->cl_revoked);
> > +		list_move(&dp->dl_recall_lru, &clp->cl_revoked);
> >  	}
> >  }
> >  
> > @@ -1458,15 +1458,14 @@ destroy_client(struct nfs4_client *clp)
> >  	spin_lock(&state_lock);
> >  	while (!list_empty(&clp->cl_delegations)) {
> >  		dp = list_entry(clp->cl_delegations.next, struct
> > nfs4_delegation, dl_perclnt);
> > -		list_del_init(&dp->dl_perclnt);
> > -		/* Ensure that deleg break won't try to requeue it
> > */
> > -		++dp->dl_time;
> > -		list_move(&dp->dl_recall_lru, &reaplist);
> > +		unhash_delegation_locked(dp);
> > +		list_add(&dp->dl_recall_lru, &reaplist);
> >  	}
> >  	spin_unlock(&state_lock);
> >  	while (!list_empty(&reaplist)) {
> >  		dp = list_entry(reaplist.next, struct
> > nfs4_delegation, dl_recall_lru);
> > -		destroy_delegation(dp);
> > +		list_del_init(&dp->dl_recall_lru);
> > +		nfs4_put_delegation(dp);
> >  	}
> >  	list_splice_init(&clp->cl_revoked, &reaplist);
> >  	while (!list_empty(&reaplist)) {
> > @@ -3662,7 +3661,7 @@ nfs4_open_delegation(struct net *net, struct
> > svc_fh *fh, open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
> >  	return;
> >  out_free:
> > -	destroy_delegation(dp);
> > +	nfs4_put_delegation(dp);
> >  out_no_deleg:
> >  	open->op_delegate_type = NFS4_OPEN_DELEGATE_NONE;
> >  	if (open->op_claim_type == NFS4_OPEN_CLAIM_PREVIOUS &&
> > @@ -3900,7 +3899,8 @@ nfs4_laundromat(struct nfsd_net *nn)
> >  			new_timeo = min(new_timeo, t);
> >  			break;
> >  		}
> > -		list_move(&dp->dl_recall_lru, &reaplist);
> > +		unhash_delegation_locked(dp);
> > +		list_add(&dp->dl_recall_lru, &reaplist);
> >  	}
> >  	spin_unlock(&state_lock);
> >  	list_for_each_safe(pos, next, &reaplist) {
> > @@ -5382,12 +5382,8 @@ static u64 nfsd_find_all_delegations(struct
> > nfs4_client *clp, u64 max, if (dp->dl_time != 0)
> >  				continue;
> >  
> > -			/*
> > -			 * Increment dl_time to ensure that
> > delegation breaks
> > -			 * don't monkey with it now that we are.
> > -			 */
> > -			++dp->dl_time;
> > -			list_move(&dp->dl_recall_lru, victims);
> > +			unhash_delegation_locked(dp);
> > +			list_add(&dp->dl_recall_lru, victims);
> >  		}
> >  		if (++count == max)
> >  			break;
> > @@ -5642,12 +5638,14 @@ nfs4_state_shutdown_net(struct net *net)
> >  	spin_lock(&state_lock);
> >  	list_for_each_safe(pos, next, &nn->del_recall_lru) {
> >  		dp = list_entry (pos, struct nfs4_delegation,
> > dl_recall_lru);
> > -		list_move(&dp->dl_recall_lru, &reaplist);
> > +		unhash_delegation_locked(dp);
> > +		list_add(&dp->dl_recall_lru, &reaplist);
> >  	}
> >  	spin_unlock(&state_lock);
> >  	list_for_each_safe(pos, next, &reaplist) {
> >  		dp = list_entry (pos, struct nfs4_delegation,
> > dl_recall_lru);
> > -		destroy_delegation(dp);
> > +		list_del_init(&dp->dl_recall_lru);
> > +		nfs4_put_delegation(dp);
> >  	}
> >  
> >  	nfsd4_client_tracking_exit(net);
> > -- 
> > 1.9.3
> > 


-- 
Jeff Layton <jlayton@primarydata.com>