Re: [PATCH v2 1/2] NFSD: keep track of the number of courtesy clients in the system

[dai.ngo@xxxxxxxxxx]

On 8/29/22 9:48 AM, Jeff Layton wrote:
> On Sun, 2022-08-28 at 17:47 -0700, Dai Ngo wrote:
> > Add counter nfs4_courtesy_client_count to nfsd_net to keep track
> > of the number of courtesy clients in the system.
> >
> > Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
> > ---
> >   fs/nfsd/netns.h     |  2 ++
> >   fs/nfsd/nfs4state.c | 20 +++++++++++++++-----
> >   2 files changed, 17 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> > index ffe17743cc74..2695dff1378a 100644
> > --- a/fs/nfsd/netns.h
> > +++ b/fs/nfsd/netns.h
> > @@ -192,6 +192,8 @@ struct nfsd_net {
> >   
> >   	atomic_t		nfs4_client_count;
> >   	int			nfs4_max_clients;
> > +
> > +	atomic_t		nfsd_courtesy_client_count;
> >   };
> >   
> >   /* Simple check to find out if a given net was properly initialized */
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index c5d199d7e6b4..3d8d7ebb5b91 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -169,7 +169,8 @@ static __be32 get_client_locked(struct nfs4_client *clp)
> >   	if (is_client_expired(clp))
> >   		return nfserr_expired;
> >   	atomic_inc(&clp->cl_rpc_users);
> > -	clp->cl_state = NFSD4_ACTIVE;
> > +	if (xchg(&clp->cl_state, NFSD4_ACTIVE) != NFSD4_ACTIVE)
> The xchg calls seem like overkill. The cl_state is protected by the
> nn->client_lock. Nothing else can race in and change it here.

I use the 'xchg' calls for convenience and readability and not for
protection in this case. But if you think this is overkill or
unnecessary then I remove it.

Fix in v2.

Thanks,
-Dai

> > +		atomic_add_unless(&nn->nfsd_courtesy_client_count, -1, 0);
> >   	return nfs_ok;
> >   }
> >   
> > @@ -190,7 +191,8 @@ renew_client_locked(struct nfs4_client *clp)
> >   
> >   	list_move_tail(&clp->cl_lru, &nn->client_lru);
> >   	clp->cl_time = ktime_get_boottime_seconds();
> > -	clp->cl_state = NFSD4_ACTIVE;
> > +	if (xchg(&clp->cl_state, NFSD4_ACTIVE) != NFSD4_ACTIVE)
> > +		atomic_add_unless(&nn->nfsd_courtesy_client_count, -1, 0);
> >   }
> >   
> >   static void put_client_renew_locked(struct nfs4_client *clp)
> > @@ -2233,6 +2235,8 @@ __destroy_client(struct nfs4_client *clp)
> >   	if (clp->cl_cb_conn.cb_xprt)
> >   		svc_xprt_put(clp->cl_cb_conn.cb_xprt);
> >   	atomic_add_unless(&nn->nfs4_client_count, -1, 0);
> > +	if (clp->cl_state != NFSD4_ACTIVE)
> > +		atomic_add_unless(&nn->nfsd_courtesy_client_count, -1, 0);
> >   	free_client(clp);
> >   	wake_up_all(&expiry_wq);
> >   }
> > @@ -4356,6 +4360,8 @@ void nfsd4_init_leases_net(struct nfsd_net *nn)
> >   	max_clients = (u64)si.totalram * si.mem_unit / (1024 * 1024 * 1024);
> >   	max_clients *= NFS4_CLIENTS_PER_GB;
> >   	nn->nfs4_max_clients = max_t(int, max_clients, NFS4_CLIENTS_PER_GB);
> > +
> > +	atomic_set(&nn->nfsd_courtesy_client_count, 0);
> >   }
> >   
> >   static void init_nfs4_replay(struct nfs4_replay *rp)
> > @@ -5864,7 +5870,7 @@ static void
> >   nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
> >   				struct laundry_time *lt)
> >   {
> > -	unsigned int maxreap, reapcnt = 0;
> > +	unsigned int oldstate, maxreap, reapcnt = 0;
> >   	struct list_head *pos, *next;
> >   	struct nfs4_client *clp;
> >   
> > @@ -5878,8 +5884,12 @@ nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
> >   			goto exp_client;
> >   		if (!state_expired(lt, clp->cl_time))
> >   			break;
> > -		if (!atomic_read(&clp->cl_rpc_users))
> > -			clp->cl_state = NFSD4_COURTESY;
> > +		oldstate = NFSD4_ACTIVE;
> > +		if (!atomic_read(&clp->cl_rpc_users)) {
> > +			oldstate = xchg(&clp->cl_state, NFSD4_COURTESY);
> > +			if (oldstate == NFSD4_ACTIVE)
> > +				atomic_inc(&nn->nfsd_courtesy_client_count);
> > +		}
> >   		if (!client_has_state(clp))
> >   			goto exp_client;
> >   		if (!nfs4_anylock_blockers(clp))