NFSD: add courteous server support for thread with only delegation

This patch provides courteous server support for delegation only.
Only expired client with delegation but no conflict and no open
or lock state is allowed to be in COURTESY state.

Delegation conflict with COURTESY/EXPIRABLE client is resolved by
setting it to EXPIRABLE, queue work for the laundromat and return
delay to the caller. Conflict is resolved when the laudromat runs
and expires the EXIRABLE client while the NFS client retries the
OPEN request. Local thread request that gets conflict is doing the
retry in _break_lease.

Client in COURTESY or EXPIRABLE state is allowed to reconnect and
continues to have access to its state. Access to the nfs4_client by
the reconnecting thread and the laundromat is serialized via the
client_lock.

Reviewed-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 67 insertions, 15 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 234e852fcdfa..24b51e822175 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -125,6 +125,8 @@ static void free_session(struct nfsd4_session *);
 static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
 static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
 
+static struct workqueue_struct *laundry_wq;
+
 static bool is_session_dead(struct nfsd4_session *ses)
 {
 	return ses->se_flags & NFS4_SESSION_DEAD;
@@ -152,6 +154,7 @@ 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;
 	return nfs_ok;
 }
 
@@ -172,6 +175,7 @@ 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;
 }
 
 static void put_client_renew_locked(struct nfs4_client *clp)
@@ -1090,6 +1094,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 	get_clnt_odstate(odstate);
 	dp->dl_type = NFS4_OPEN_DELEGATE_READ;
 	dp->dl_retries = 1;
+	dp->dl_recalled = false;
 	nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
 		      &nfsd4_cb_recall_ops, NFSPROC4_CLNT_CB_RECALL);
 	get_nfs4_file(fp);
@@ -2004,6 +2009,8 @@ static struct nfs4_client *alloc_client(struct xdr_netobj name)
 	idr_init(&clp->cl_stateids);
 	atomic_set(&clp->cl_rpc_users, 0);
 	clp->cl_cb_state = NFSD4_CB_UNKNOWN;
+	clp->cl_state = NFSD4_ACTIVE;
+	atomic_set(&clp->cl_delegs_in_recall, 0);
 	INIT_LIST_HEAD(&clp->cl_idhash);
 	INIT_LIST_HEAD(&clp->cl_openowners);
 	INIT_LIST_HEAD(&clp->cl_delegations);
@@ -4694,9 +4701,18 @@ nfsd_break_deleg_cb(struct file_lock *fl)
 	bool ret = false;
 	struct nfs4_delegation *dp = (struct nfs4_delegation *)fl->fl_owner;
 	struct nfs4_file *fp = dp->dl_stid.sc_file;
+	struct nfs4_client *clp = dp->dl_stid.sc_client;
+	struct nfsd_net *nn;
 
 	trace_nfsd_cb_recall(&dp->dl_stid);
 
+	dp->dl_recalled = true;
+	atomic_inc(&clp->cl_delegs_in_recall);
+	if (try_to_expire_client(clp)) {
+		nn = net_generic(clp->net, nfsd_net_id);
+		mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
+	}
+
 	/*
 	 * We don't want the locks code to timeout the lease for us;
 	 * we'll remove it ourself if a delegation isn't returned
@@ -4739,9 +4755,14 @@ static int
 nfsd_change_deleg_cb(struct file_lock *onlist, int arg,
 		     struct list_head *dispose)
 {
-	if (arg & F_UNLCK)
+	struct nfs4_delegation *dp = (struct nfs4_delegation *)onlist->fl_owner;
+	struct nfs4_client *clp = dp->dl_stid.sc_client;
+
+	if (arg & F_UNLCK) {
+		if (dp->dl_recalled)
+			atomic_dec(&clp->cl_delegs_in_recall);
 		return lease_modify(onlist, arg, dispose);
-	else
+	} else
 		return -EAGAIN;
 }
 
@@ -5605,6 +5626,49 @@ static void nfsd4_ssc_expire_umount(struct nfsd_net *nn)
 }
 #endif
 
+/*
+ * place holder for now, no check for lock blockers yet
+ */
+static bool
+nfs4_anylock_blockers(struct nfs4_client *clp)
+{
+	if (atomic_read(&clp->cl_delegs_in_recall) ||
+			client_has_openowners(clp)  ||
+			!list_empty(&clp->async_copies))
+		return true;
+	return false;
+}
+
+static void
+nfs4_get_client_reaplist(struct nfsd_net *nn, struct list_head *reaplist,
+				struct laundry_time *lt)
+{
+	struct list_head *pos, *next;
+	struct nfs4_client *clp;
+
+	INIT_LIST_HEAD(reaplist);
+	spin_lock(&nn->client_lock);
+	list_for_each_safe(pos, next, &nn->client_lru) {
+		clp = list_entry(pos, struct nfs4_client, cl_lru);
+		if (clp->cl_state == NFSD4_EXPIRABLE)
+			goto exp_client;
+		if (!state_expired(lt, clp->cl_time))
+			break;
+		if (!atomic_read(&clp->cl_rpc_users))
+			clp->cl_state = NFSD4_COURTESY;
+		if (!client_has_state(clp) ||
+				ktime_get_boottime_seconds() >=
+				(clp->cl_time + NFSD_COURTESY_CLIENT_TIMEOUT))
+			goto exp_client;
+		if (nfs4_anylock_blockers(clp)) {
+exp_client:
+			if (!mark_client_expired_locked(clp))
+				list_add(&clp->cl_lru, reaplist);
+		}
+	}
+	spin_unlock(&nn->client_lock);
+}
+
 static time64_t
 nfs4_laundromat(struct nfsd_net *nn)
 {
@@ -5627,7 +5691,6 @@ nfs4_laundromat(struct nfsd_net *nn)
 		goto out;
 	}
 	nfsd4_end_grace(nn);
-	INIT_LIST_HEAD(&reaplist);
 
 	spin_lock(&nn->s2s_cp_lock);
 	idr_for_each_entry(&nn->s2s_cp_stateids, cps_t, i) {
@@ -5637,17 +5700,7 @@ nfs4_laundromat(struct nfsd_net *nn)
 			_free_cpntf_state_locked(nn, cps);
 	}
 	spin_unlock(&nn->s2s_cp_lock);
-
-	spin_lock(&nn->client_lock);
-	list_for_each_safe(pos, next, &nn->client_lru) {
-		clp = list_entry(pos, struct nfs4_client, cl_lru);
-		if (!state_expired(&lt, clp->cl_time))
-			break;
-		if (mark_client_expired_locked(clp))
-			continue;
-		list_add(&clp->cl_lru, &reaplist);
-	}
-	spin_unlock(&nn->client_lock);
+	nfs4_get_client_reaplist(nn, &reaplist, &lt);
 	list_for_each_safe(pos, next, &reaplist) {
 		clp = list_entry(pos, struct nfs4_client, cl_lru);
 		trace_nfsd_clid_purged(&clp->cl_clientid);
@@ -5722,7 +5775,6 @@ out:
 	return max_t(time64_t, lt.new_timeo, NFSD_LAUNDROMAT_MINTIMEOUT);
 }
 
-static struct workqueue_struct *laundry_wq;
 static void laundromat_main(struct work_struct *);
 
 static void