From: "J. Bruce Fields" <bfields@fieldses.org>
To: Scott Mayhew <smayhew@redhat.com>
Cc: jlayton@kernel.org, linux-nfs@vger.kernel.org
Subject: Re: [PATCH v2 3/3] nfsd: keep a tally of RECLAIM_COMPLETE operations when using nfsdcld
Date: Wed, 19 Dec 2018 17:21:47 -0500 [thread overview]
Message-ID: <20181219222147.GA31570@fieldses.org> (raw)
In-Reply-To: <20181219220545.GS27213@coeurl.usersys.redhat.com>
On Wed, Dec 19, 2018 at 05:05:45PM -0500, Scott Mayhew wrote:
> On Wed, 19 Dec 2018, J. Bruce Fields wrote:
>
> > On Tue, Dec 18, 2018 at 09:29:26AM -0500, Scott Mayhew wrote:
> > > + if (!nfsd4_find_reclaim_client(clp->cl_name, nn))
> > > + return;
> > > + if (atomic_inc_return(&nn->nr_reclaim_complete) ==
> > > + nn->reclaim_str_hashtbl_size) {
> > > + printk(KERN_INFO "NFSD: all clients done reclaiming, ending NFSv4 grace period (net %x)\n",
> > > + clp->net->ns.inum);
> > > + nfsd4_end_grace(nn);
> > > + }
> > > +}
> > > +
> > > +static void dec_reclaim_complete(struct nfs4_client *clp)
> > > +{
> > > + struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
> > > +
> > > + if (!nn->track_reclaim_completes)
> > > + return;
> > > + if (!test_bit(NFSD4_CLIENT_RECLAIM_COMPLETE, &clp->cl_flags))
> > > + return;
> > > + if (nfsd4_find_reclaim_client(clp->cl_name, nn))
> > > + atomic_dec(&nn->nr_reclaim_complete);
> > > +}
> > > +
> > > static void expire_client(struct nfs4_client *clp)
> > > {
> > > unhash_client(clp);
> > > nfsd4_client_record_remove(clp);
> > > + dec_reclaim_complete(clp);
> > > __destroy_client(clp);
> > > }
> >
> > This doesn't look right to me. If a client reclaims and then
> > immediately calls DESTROY_CLIENTID or something--that should still count
> > as a reclaim, and that shouldn't prevent us from ending the grace period
> > early.
> >
> > I think dec_reclaim_complete is unnecessary.
>
> What if a client sends a RECLAIM_COMPLETE, then reboots and sends an
> EXCHANGE_ID, CREATE_SESSION, and RECLAIM_COMPLETE while the server is
> still in grace? The count would be too high then and the server could
> exit grace before all the clients have reclaimed. I actually added
> that at Jeff's suggestion because he was seeing it with nfs-ganesha.
Oh boy.
(Thinks.)
Once it issues a DESTROY_CLIENTID or an EXCHANGE_ID that removes the
previous client instance's state, it's got no locks to reclaim any more.
(It can't have gotten any *new* ones, since we're still in the grace
period.)
It's effectively a brand new client. Only reclaiming clients should
bump that counter.
We certainly shouldn't be waiting for it to RECLAIM_COMPLETE to end the
grace period, that client just doesn't matter any more.
I think?
--b.
next prev parent reply other threads:[~2018-12-19 22:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 14:29 [PATCH v2 0/3] un-deprecate nfsdcld Scott Mayhew
2018-12-18 14:29 ` [PATCH v2 1/3] nfsd: make nfs4_client_reclaim use an xdr_netobj instead of a fixed char array Scott Mayhew
2018-12-18 14:29 ` [PATCH v2 2/3] nfsd: un-deprecate nfsdcld Scott Mayhew
2018-12-19 21:23 ` Jeff Layton
2018-12-19 22:11 ` Scott Mayhew
2018-12-20 0:19 ` Jeff Layton
2018-12-20 1:59 ` J. Bruce Fields
2018-12-20 15:24 ` Jeff Layton
2018-12-18 14:29 ` [PATCH v2 3/3] nfsd: keep a tally of RECLAIM_COMPLETE operations when using nfsdcld Scott Mayhew
2018-12-19 17:46 ` J. Bruce Fields
2018-12-19 21:57 ` Scott Mayhew
2018-12-19 18:28 ` J. Bruce Fields
2018-12-19 22:01 ` Scott Mayhew
2018-12-19 18:36 ` J. Bruce Fields
2018-12-19 22:05 ` Scott Mayhew
2018-12-19 22:21 ` J. Bruce Fields [this message]
2018-12-19 22:43 ` J. Bruce Fields
2018-12-20 16:36 ` Scott Mayhew
2018-12-20 17:32 ` Jeff Layton
2018-12-20 17:29 ` Jeff Layton
2018-12-20 18:05 ` J. Bruce Fields
2018-12-20 18:26 ` Jeff Layton
2018-12-20 19:02 ` J. Bruce Fields
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