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Date:   Thu, 11 Aug 2022 01:47:32 +0800
From:   "D. Wythe" <alibuda@...ux.alibaba.com>
To:     kgraul@...ux.ibm.com, wenjia@...ux.ibm.com
Cc:     kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: [PATCH net-next 01/10] net/smc: remove locks smc_client_lgr_pending and smc_server_lgr_pending

From: "D. Wythe" <alibuda@...ux.alibaba.com>

This patch attempts to remove locks named smc_client_lgr_pending and
smc_server_lgr_pending, which aim to serialize the creation of link
group. However, once link group existed already, those locks are
meaningless, worse still, they make incoming connections have to be
queued one after the other.

Now, the creation of link group is no longer generated by competition,
but allocated through following strategy.

1. Try to find a suitable link group, if successd, current connection
is considered as NON first contact connection. ends.

2. Check the number of connections currently waiting for a suitable
link group to be created, if it is not less that the number of link
groups to be created multiplied by (SMC_RMBS_PER_LGR_MAX - 1), then
increase the number of link groups to be created, current connection
is considered as the first contact connection. ends.

3. Increase the number of connections currently waiting, and wait
for woken up.

4. Decrease the number of connections currently waiting, goto 1.

We wake up the connection that was put to sleep in stage 3 through
the SMC link state change event. Once the link moves out of the
SMC_LNK_ACTIVATING state, decrease the number of link groups to
be created, and then wake up at most (SMC_RMBS_PER_LGR_MAX - 1)
connections.

In the iplementation, we introduce the concept of lnk cluster, which is
a collection of links with the same characteristics (see
smcr_lnk_cluster_cmpfn() with more details), which makes it possible to
wake up efficiently in the scenario of N v.s 1.

Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
---
 net/smc/af_smc.c   |  11 +-
 net/smc/smc_core.c | 356 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 net/smc/smc_core.h |  48 ++++++++
 net/smc/smc_llc.c  |   9 +-
 4 files changed, 411 insertions(+), 13 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 79c1318..af4b0aa 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1194,10 +1194,8 @@ static int smc_connect_rdma(struct smc_sock *smc,
 	if (reason_code)
 		return reason_code;
 
-	mutex_lock(&smc_client_lgr_pending);
 	reason_code = smc_conn_create(smc, ini);
 	if (reason_code) {
-		mutex_unlock(&smc_client_lgr_pending);
 		return reason_code;
 	}
 
@@ -1289,7 +1287,6 @@ static int smc_connect_rdma(struct smc_sock *smc,
 		if (reason_code)
 			goto connect_abort;
 	}
-	mutex_unlock(&smc_client_lgr_pending);
 
 	smc_copy_sock_settings_to_clc(smc);
 	smc->connect_nonblock = 0;
@@ -1299,7 +1296,6 @@ static int smc_connect_rdma(struct smc_sock *smc,
 	return 0;
 connect_abort:
 	smc_conn_abort(smc, ini->first_contact_local);
-	mutex_unlock(&smc_client_lgr_pending);
 	smc->connect_nonblock = 0;
 
 	return reason_code;
@@ -2377,7 +2373,8 @@ static void smc_listen_work(struct work_struct *work)
 	if (rc)
 		goto out_decl;
 
-	mutex_lock(&smc_server_lgr_pending);
+	if (ini->is_smcd)
+		mutex_lock(&smc_server_lgr_pending);
 	smc_close_init(new_smc);
 	smc_rx_init(new_smc);
 	smc_tx_init(new_smc);
@@ -2415,7 +2412,6 @@ static void smc_listen_work(struct work_struct *work)
 					    ini->first_contact_local, ini);
 		if (rc)
 			goto out_unlock;
-		mutex_unlock(&smc_server_lgr_pending);
 	}
 	smc_conn_save_peer_info(new_smc, cclc);
 	smc_listen_out_connected(new_smc);
@@ -2423,7 +2419,8 @@ static void smc_listen_work(struct work_struct *work)
 	goto out_free;
 
 out_unlock:
-	mutex_unlock(&smc_server_lgr_pending);
+	if (ini->is_smcd)
+		mutex_unlock(&smc_server_lgr_pending);
 out_decl:
 	smc_listen_decline(new_smc, rc, ini ? ini->first_contact_local : 0,
 			   proposal_version);
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index ff49a11..a3338cc 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -46,6 +46,10 @@ struct smc_lgr_list smc_lgr_list = {	/* established link groups */
 	.num = 0,
 };
 
+struct smc_lgr_manager smc_lgr_manager = {
+	.lock = __SPIN_LOCK_UNLOCKED(smc_lgr_manager.lock),
+};
+
 static atomic_t lgr_cnt = ATOMIC_INIT(0); /* number of existing link groups */
 static DECLARE_WAIT_QUEUE_HEAD(lgrs_deleted);
 
@@ -55,6 +59,282 @@ static void smc_buf_free(struct smc_link_group *lgr, bool is_rmb,
 
 static void smc_link_down_work(struct work_struct *work);
 
+/* SMC-R lnk cluster compare func
+ * All lnks that meet the description conditions of this function
+ * are logically aggregated, called lnk cluster.
+ * For the server side, lnk cluster is used to determine whether
+ * a new group needs to be created when processing new imcoming connections.
+ * For the client side, lnk cluster is used to determine whether
+ * to wait for link ready (in other words, first contact ready).
+ */
+static int smcr_lnk_cluster_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct smc_lnk_cluster_compare_arg *key = arg->key;
+	const struct smc_lnk_cluster *lnkc = obj;
+
+	if (memcmp(key->peer_systemid, lnkc->peer_systemid, SMC_SYSTEMID_LEN))
+		return 1;
+
+	if (memcmp(key->peer_gid, lnkc->peer_gid, SMC_GID_SIZE))
+		return 1;
+
+	if ((key->role == SMC_SERV || key->clcqpn == lnkc->clcqpn) &&
+	    (key->smcr_version == SMC_V2 ||
+	    !memcmp(key->peer_mac, lnkc->peer_mac, ETH_ALEN)))
+		return 0;
+
+	return 1;
+}
+
+/* SMC-R lnk cluster hash func */
+static u32 smcr_lnk_cluster_hashfn(const void *data, u32 len, u32 seed)
+{
+	const struct smc_lnk_cluster *lnkc = data;
+
+	return jhash2((u32 *)lnkc->peer_systemid, SMC_SYSTEMID_LEN / sizeof(u32), seed)
+		+ (lnkc->role == SMC_SERV) ? 0 : lnkc->clcqpn;
+}
+
+/* SMC-R lnk cluster compare arg hash func */
+static u32 smcr_lnk_cluster_compare_arg_hashfn(const void *data, u32 len, u32 seed)
+{
+	const struct smc_lnk_cluster_compare_arg *key = data;
+
+	return jhash2((u32 *)key->peer_systemid, SMC_SYSTEMID_LEN / sizeof(u32), seed)
+		+ (key->role == SMC_SERV) ? 0 : key->clcqpn;
+}
+
+static const struct rhashtable_params smcr_lnk_cluster_rhl_params = {
+	.head_offset = offsetof(struct smc_lnk_cluster, rnode),
+	.key_len = sizeof(struct smc_lnk_cluster_compare_arg),
+	.obj_cmpfn = smcr_lnk_cluster_cmpfn,
+	.obj_hashfn = smcr_lnk_cluster_hashfn,
+	.hashfn = smcr_lnk_cluster_compare_arg_hashfn,
+	.automatic_shrinking = true,
+};
+
+/* hold a reference for smc_lnk_cluster */
+static inline void smc_lnk_cluster_hold(struct smc_lnk_cluster *lnkc)
+{
+	if (likely(lnkc))
+		refcount_inc(&lnkc->ref);
+}
+
+/* release a reference for smc_lnk_cluster */
+static inline void smc_lnk_cluster_put(struct smc_lnk_cluster *lnkc)
+{
+	bool do_free = false;
+
+	if (!lnkc)
+		return;
+
+	if (refcount_dec_not_one(&lnkc->ref))
+		return;
+
+	spin_lock_bh(&smc_lgr_manager.lock);
+	/* last ref */
+	if (refcount_dec_and_test(&lnkc->ref)) {
+		do_free = true;
+		rhashtable_remove_fast(&smc_lgr_manager.lnk_cluster_maps, &lnkc->rnode,
+				       smcr_lnk_cluster_rhl_params);
+	}
+	spin_unlock_bh(&smc_lgr_manager.lock);
+	if (do_free)
+		kfree(lnkc);
+}
+
+/* Get or create smc_lnk_cluster by key
+ * This function will hold a reference of returned smc_lnk_cluster
+ * or create a new smc_lnk_cluster with the reference initialized to 1。
+ * caller MUST call smc_lnk_cluster_put after this.
+ */
+static inline struct smc_lnk_cluster *
+smcr_lnk_get_or_create_cluster(struct smc_lnk_cluster_compare_arg *key)
+{
+	struct smc_lnk_cluster *lnkc, *tmp_lnkc;
+	bool busy_retry;
+	int err;
+
+	/* serving a hardware or software interrupt, or preemption is disabled */
+	busy_retry = !in_interrupt();
+
+	spin_lock_bh(&smc_lgr_manager.lock);
+	lnkc = rhashtable_lookup_fast(&smc_lgr_manager.lnk_cluster_maps, key,
+				      smcr_lnk_cluster_rhl_params);
+	if (!lnkc) {
+		lnkc = kzalloc(sizeof(*lnkc), GFP_ATOMIC);
+		if (unlikely(!lnkc))
+			goto fail;
+
+		/* init cluster */
+		spin_lock_init(&lnkc->lock);
+		lnkc->role = key->role;
+		if (key->role == SMC_CLNT)
+			lnkc->clcqpn = key->clcqpn;
+		init_waitqueue_head(&lnkc->first_contact_waitqueue);
+		memcpy(lnkc->peer_systemid, key->peer_systemid, SMC_SYSTEMID_LEN);
+		memcpy(lnkc->peer_gid, key->peer_gid, SMC_GID_SIZE);
+		memcpy(lnkc->peer_mac, key->peer_mac, ETH_ALEN);
+		refcount_set(&lnkc->ref, 1);
+
+		do {
+			err = rhashtable_insert_fast(&smc_lgr_manager.lnk_cluster_maps,
+						     &lnkc->rnode, smcr_lnk_cluster_rhl_params);
+
+			/* success or fatal error */
+			if (err != -EBUSY)
+				break;
+
+			/* impossible in fact right now */
+			if (unlikely(!busy_retry)) {
+				pr_warn_ratelimited("smc: create lnk cluster in softirq\n");
+				break;
+			}
+
+			spin_unlock_bh(&smc_lgr_manager.lock);
+			/* yeild */
+			cond_resched();
+			spin_lock_bh(&smc_lgr_manager.lock);
+
+			/* after spin_unlock_bh(), lnk_cluster_maps may be changed */
+			tmp_lnkc = rhashtable_lookup_fast(&smc_lgr_manager.lnk_cluster_maps, key,
+							  smcr_lnk_cluster_rhl_params);
+
+			if (unlikely(tmp_lnkc)) {
+				pr_warn_ratelimited("smc: create cluster failed dues to duplicat key");
+				kfree(lnkc);
+				lnkc = NULL;
+				goto fail;
+			}
+		} while (1);
+
+		if (unlikely(err)) {
+			pr_warn_ratelimited("smc: rhashtable_insert_fast failed (%d)", err);
+			kfree(lnkc);
+			lnkc = NULL;
+		}
+	} else {
+		smc_lnk_cluster_hold(lnkc);
+	}
+fail:
+	spin_unlock_bh(&smc_lgr_manager.lock);
+	return lnkc;
+}
+
+/* Get or create a smc_lnk_cluster by lnk
+ * caller MUST call smc_lnk_cluster_put after this.
+ */
+static inline struct smc_lnk_cluster *smcr_lnk_get_cluster(struct smc_link *lnk)
+{
+	struct smc_lnk_cluster_compare_arg key;
+	struct smc_link_group *lgr;
+
+	lgr = lnk->lgr;
+	if (!lgr || lgr->is_smcd)
+		return NULL;
+
+	key.smcr_version = lgr->smc_version;
+	key.peer_systemid = lgr->peer_systemid;
+	key.peer_gid = lnk->peer_gid;
+	key.peer_mac = lnk->peer_mac;
+	key.role	 = lgr->role;
+	if (key.role == SMC_CLNT)
+		key.clcqpn = lnk->peer_qpn;
+
+	return smcr_lnk_get_or_create_cluster(&key);
+}
+
+/* Get or create a smc_lnk_cluster by ini
+ * caller MUST call smc_lnk_cluster_put after this.
+ */
+static inline struct smc_lnk_cluster *
+smcr_lnk_get_cluster_by_ini(struct smc_init_info *ini, int role)
+{
+	struct smc_lnk_cluster_compare_arg key;
+
+	if (ini->is_smcd)
+		return NULL;
+
+	key.smcr_version = ini->smcr_version;
+	key.peer_systemid = ini->peer_systemid;
+	key.peer_gid = ini->peer_gid;
+	key.peer_mac = ini->peer_mac;
+	key.role	= role;
+	if (role == SMC_CLNT)
+		key.clcqpn	= ini->ib_clcqpn;
+
+	return smcr_lnk_get_or_create_cluster(&key);
+}
+
+/* callback when smc link state change */
+void smcr_lnk_cluster_on_lnk_state(struct smc_link *lnk)
+{
+	struct smc_lnk_cluster *lnkc;
+	int nr = 0;
+
+	/* barrier for lnk->state */
+	smp_mb();
+
+	/* only first link can made connections block on
+	 * first_contact_waitqueue
+	 */
+	if (lnk->link_idx != SMC_SINGLE_LINK)
+		return;
+
+	/* state already seen  */
+	if (lnk->state_record & SMC_LNK_STATE_BIT(lnk->state))
+		return;
+
+	lnkc = smcr_lnk_get_cluster(lnk);
+
+	if (unlikely(!lnkc))
+		return;
+
+	spin_lock_bh(&lnkc->lock);
+
+	/* all lnk state change should be
+	 * 1. SMC_LNK_UNUSED -> SMC_LNK_TEAR_DWON (link init failed)
+	 * 2. SMC_LNK_UNUSED -> SMC_LNK_ACTIVATING -> SMC_LNK_TEAR_DWON
+	 * 3. SMC_LNK_UNUSED -> SMC_LNK_ACTIVATING -> SMC_LNK_INACTIVE -> SMC_LNK_TEAR_DWON
+	 * 4. SMC_LNK_UNUSED -> SMC_LNK_ACTIVATING -> SMC_LNK_INACTIVE -> SMC_LNK_TEAR_DWON
+	 * 5. SMC_LNK_UNUSED -> SMC_LNK_ATIVATING -> SMC_LNK_ACTIVE ->SMC_LNK_INACTIVE
+	 * -> SMC_LNK_TEAR_DWON
+	 */
+	switch (lnk->state) {
+	case SMC_LNK_ACTIVATING:
+		/* It's safe to hold a reference without lock
+		 * dues to the smcr_lnk_get_cluster already hold one
+		 */
+		smc_lnk_cluster_hold(lnkc);
+		break;
+	case SMC_LNK_TEAR_DWON:
+		if (lnk->state_record & SMC_LNK_STATE_BIT(SMC_LNK_ACTIVATING))
+			/* smc_lnk_cluster_hold in SMC_LNK_ACTIVATING */
+			smc_lnk_cluster_put(lnkc);
+		fallthrough;
+	case SMC_LNK_ACTIVE:
+	case SMC_LNK_INACTIVE:
+		if (!(lnk->state_record &
+			(SMC_LNK_STATE_BIT(SMC_LNK_ACTIVE)
+			| SMC_LNK_STATE_BIT(SMC_LNK_INACTIVE)))) {
+			lnkc->pending_capability -= (SMC_RMBS_PER_LGR_MAX - 1);
+			/* TODO: wakeup just one to perfrom first contact
+			 * if record state has no SMC_LNK_ACTIVE
+			 */
+			nr = SMC_RMBS_PER_LGR_MAX - 1;
+		}
+		break;
+	case SMC_LNK_UNUSED:
+		pr_warn_ratelimited("net/smc: invalid lnk state. ");
+		break;
+	}
+	SMC_LNK_STATE_RECORD(lnk, lnk->state);
+	spin_unlock_bh(&lnkc->lock);
+	if (nr)
+		wake_up_nr(&lnkc->first_contact_waitqueue, nr);
+	smc_lnk_cluster_put(lnkc);	/* smc_lnk_cluster_hold in smcr_lnk_get_cluster */
+}
+
 /* return head of link group list and its lock for a given link group */
 static inline struct list_head *smc_lgr_list_head(struct smc_link_group *lgr,
 						  spinlock_t **lgr_lock)
@@ -651,8 +931,10 @@ static void smcr_lgr_link_deactivate_all(struct smc_link_group *lgr)
 	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
 		struct smc_link *lnk = &lgr->lnk[i];
 
-		if (smc_link_sendable(lnk))
+		if (smc_link_sendable(lnk)) {
 			lnk->state = SMC_LNK_INACTIVE;
+			smcr_lnk_cluster_on_lnk_state(lnk);
+		}
 	}
 	wake_up_all(&lgr->llc_msg_waiter);
 	wake_up_all(&lgr->llc_flow_waiter);
@@ -762,6 +1044,9 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk,
 	atomic_set(&lnk->conn_cnt, 0);
 	smc_llc_link_set_uid(lnk);
 	INIT_WORK(&lnk->link_down_wrk, smc_link_down_work);
+	lnk->peer_qpn = ini->ib_clcqpn;
+	memcpy(lnk->peer_gid, ini->peer_gid, SMC_GID_SIZE);
+	memcpy(lnk->peer_mac, ini->peer_mac, sizeof(lnk->peer_mac));
 	if (!lnk->smcibdev->initialized) {
 		rc = (int)smc_ib_setup_per_ibdev(lnk->smcibdev);
 		if (rc)
@@ -792,6 +1077,7 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk,
 	if (rc)
 		goto destroy_qp;
 	lnk->state = SMC_LNK_ACTIVATING;
+	smcr_lnk_cluster_on_lnk_state(lnk);
 	return 0;
 
 destroy_qp:
@@ -806,6 +1092,8 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk,
 	smc_ibdev_cnt_dec(lnk);
 	put_device(&lnk->smcibdev->ibdev->dev);
 	smcibdev = lnk->smcibdev;
+	lnk->state = SMC_LNK_TEAR_DWON;
+	smcr_lnk_cluster_on_lnk_state(lnk);
 	memset(lnk, 0, sizeof(struct smc_link));
 	lnk->state = SMC_LNK_UNUSED;
 	if (!atomic_dec_return(&smcibdev->lnk_cnt))
@@ -1263,6 +1551,8 @@ void smcr_link_clear(struct smc_link *lnk, bool log)
 	if (!lnk->lgr || lnk->clearing ||
 	    lnk->state == SMC_LNK_UNUSED)
 		return;
+	lnk->state = SMC_LNK_TEAR_DWON;
+	smcr_lnk_cluster_on_lnk_state(lnk);
 	lnk->clearing = 1;
 	lnk->peer_qpn = 0;
 	smc_llc_link_clear(lnk, log);
@@ -1712,6 +2002,7 @@ void smcr_link_down_cond(struct smc_link *lnk)
 {
 	if (smc_link_downing(&lnk->state)) {
 		trace_smcr_link_down(lnk, __builtin_return_address(0));
+		smcr_lnk_cluster_on_lnk_state(lnk);
 		smcr_link_down(lnk);
 	}
 }
@@ -1721,6 +2012,7 @@ void smcr_link_down_cond_sched(struct smc_link *lnk)
 {
 	if (smc_link_downing(&lnk->state)) {
 		trace_smcr_link_down(lnk, __builtin_return_address(0));
+		smcr_lnk_cluster_on_lnk_state(lnk);
 		schedule_work(&lnk->link_down_wrk);
 	}
 }
@@ -1850,11 +2142,13 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 {
 	struct smc_connection *conn = &smc->conn;
 	struct net *net = sock_net(&smc->sk);
+	DECLARE_WAITQUEUE(wait, current);
+	struct smc_lnk_cluster *lnkc = NULL;
 	struct list_head *lgr_list;
 	struct smc_link_group *lgr;
 	enum smc_lgr_role role;
 	spinlock_t *lgr_lock;
-	int rc = 0;
+	int rc = 0, timeo = CLC_WAIT_TIME;
 
 	lgr_list = ini->is_smcd ? &ini->ism_dev[ini->ism_selected]->lgr_list :
 				  &smc_lgr_list.list;
@@ -1862,12 +2156,26 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 				  &smc_lgr_list.lock;
 	ini->first_contact_local = 1;
 	role = smc->listen_smc ? SMC_SERV : SMC_CLNT;
-	if (role == SMC_CLNT && ini->first_contact_peer)
+
+	if (!ini->is_smcd) {
+		lnkc = smcr_lnk_get_cluster_by_ini(ini, role);
+		if (unlikely(!lnkc))
+			return SMC_CLC_DECL_INTERR;
+	}
+
+	if (role == SMC_CLNT && ini->first_contact_peer) {
+		/* first_contact */
+		spin_lock_bh(&lnkc->lock);
+		lnkc->pending_capability += (SMC_RMBS_PER_LGR_MAX - 1);
+		spin_unlock_bh(&lnkc->lock);
 		/* create new link group as well */
 		goto create;
+	}
 
 	/* determine if an existing link group can be reused */
 	spin_lock_bh(lgr_lock);
+	spin_lock(&lnkc->lock);
+again:
 	list_for_each_entry(lgr, lgr_list, list) {
 		write_lock_bh(&lgr->conns_lock);
 		if ((ini->is_smcd ?
@@ -1894,9 +2202,33 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 		}
 		write_unlock_bh(&lgr->conns_lock);
 	}
+	if (lnkc && ini->first_contact_local) {
+		if (lnkc->pending_capability > lnkc->conns_pending) {
+			lnkc->conns_pending++;
+			add_wait_queue(&lnkc->first_contact_waitqueue, &wait);
+			spin_unlock(&lnkc->lock);
+			spin_unlock_bh(lgr_lock);
+			set_current_state(TASK_INTERRUPTIBLE);
+			/* need to wait at least once first contact done */
+			timeo = schedule_timeout(timeo);
+			set_current_state(TASK_RUNNING);
+			remove_wait_queue(&lnkc->first_contact_waitqueue, &wait);
+			spin_lock_bh(lgr_lock);
+			spin_lock(&lnkc->lock);
+
+			lnkc->conns_pending--;
+			if (timeo)
+				goto again;
+		}
+		if (role == SMC_SERV) {
+			/* first_contact */
+			lnkc->pending_capability += (SMC_RMBS_PER_LGR_MAX - 1);
+		}
+	}
+	spin_unlock(&lnkc->lock);
 	spin_unlock_bh(lgr_lock);
 	if (rc)
-		return rc;
+		goto out;
 
 	if (role == SMC_CLNT && !ini->first_contact_peer &&
 	    ini->first_contact_local) {
@@ -1904,7 +2236,8 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 		 * a new one
 		 * send out_of_sync decline, reason synchr. error
 		 */
-		return SMC_CLC_DECL_SYNCERR;
+		rc = SMC_CLC_DECL_SYNCERR;
+		goto out;
 	}
 
 create:
@@ -1941,6 +2274,8 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 #endif
 
 out:
+	/* smc_lnk_cluster_hold in smcr_lnk_get_or_create_cluster */
+	smc_lnk_cluster_put(lnkc);
 	return rc;
 }
 
@@ -2599,12 +2934,23 @@ static int smc_core_reboot_event(struct notifier_block *this,
 
 int __init smc_core_init(void)
 {
+	/* init smc lnk cluster maps */
+	rhashtable_init(&smc_lgr_manager.lnk_cluster_maps, &smcr_lnk_cluster_rhl_params);
 	return register_reboot_notifier(&smc_reboot_notifier);
 }
 
+static void smc_lnk_cluster_free_cb(void *ptr, void *arg)
+{
+	pr_warn("smc: smc lnk cluster refcnt leak.\n");
+	kfree(ptr);
+}
+
 /* Called (from smc_exit) when module is removed */
 void smc_core_exit(void)
 {
 	unregister_reboot_notifier(&smc_reboot_notifier);
 	smc_lgrs_shutdown();
+	/* destroy smc lnk cluster maps */
+	rhashtable_free_and_destroy(&smc_lgr_manager.lnk_cluster_maps, smc_lnk_cluster_free_cb,
+				    NULL);
 }
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index fe8b524..199f533 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -15,6 +15,7 @@
 #include <linux/atomic.h>
 #include <linux/smc.h>
 #include <linux/pci.h>
+#include <linux/rhashtable.h>
 #include <rdma/ib_verbs.h>
 #include <net/genetlink.h>
 
@@ -29,18 +30,62 @@ struct smc_lgr_list {			/* list of link group definition */
 	u32			num;	/* unique link group number */
 };
 
+struct smc_lgr_manager {		/* manager for link group */
+	struct rhashtable	lnk_cluster_maps;	/* maps of smc_lnk_cluster */
+	spinlock_t		lock;	/* lock for lgr_cm_maps */
+};
+
+struct smc_lnk_cluster {
+	struct rhash_head	rnode;	/* node for rhashtable */
+	struct wait_queue_head	first_contact_waitqueue;
+					/* queue for non first contact to wait
+					 * first contact to be established.
+					 */
+	spinlock_t		lock;	/* protection for link group */
+	refcount_t		ref;	/* refcount for cluster */
+	unsigned long		pending_capability;
+					/* maximum pending number of connections that
+					 * need wait first contact complete.
+					 */
+	unsigned long		conns_pending;
+					/* connections that are waiting for first contact
+					 * complete
+					 */
+	u8		peer_systemid[SMC_SYSTEMID_LEN];
+	u8		peer_mac[ETH_ALEN];	/* = gid[8:10||13:15] */
+	u8		peer_gid[SMC_GID_SIZE];	/* gid of peer*/
+	int		clcqpn;
+	int		role;
+};
+
 enum smc_lgr_role {		/* possible roles of a link group */
 	SMC_CLNT,	/* client */
 	SMC_SERV	/* server */
 };
 
+struct smc_lnk_cluster_compare_arg	/* key for smc_lnk_cluster */
+{
+	int	smcr_version;
+	enum smc_lgr_role role;
+	u8	*peer_systemid;
+	u8	*peer_gid;
+	u8	*peer_mac;
+	int clcqpn;
+};
+
 enum smc_link_state {			/* possible states of a link */
 	SMC_LNK_UNUSED,		/* link is unused */
 	SMC_LNK_INACTIVE,	/* link is inactive */
 	SMC_LNK_ACTIVATING,	/* link is being activated */
 	SMC_LNK_ACTIVE,		/* link is active */
+	SMC_LNK_TEAR_DWON,	/* link is tear down */
 };
 
+#define SMC_LNK_STATE_BIT(state)	(1 << (state))
+
+#define	SMC_LNK_STATE_RECORD(lnk, state)	\
+	((lnk)->state_record |= SMC_LNK_STATE_BIT(state))
+
 #define SMC_WR_BUF_SIZE		48	/* size of work request buffer */
 #define SMC_WR_BUF_V2_SIZE	8192	/* size of v2 work request buffer */
 
@@ -145,6 +190,7 @@ struct smc_link {
 	int			ndev_ifidx; /* network device ifindex */
 
 	enum smc_link_state	state;		/* state of link */
+	int			state_record;		/* record of previous state */
 	struct delayed_work	llc_testlink_wrk; /* testlink worker */
 	struct completion	llc_testlink_resp; /* wait for rx of testlink */
 	int			llc_testlink_time; /* testlink interval */
@@ -557,6 +603,8 @@ struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
 int smcr_nl_get_link(struct sk_buff *skb, struct netlink_callback *cb);
 int smcd_nl_get_lgr(struct sk_buff *skb, struct netlink_callback *cb);
 
+void smcr_lnk_cluster_on_lnk_state(struct smc_link *lnk);
+
 static inline struct smc_link_group *smc_get_lgr(struct smc_link *link)
 {
 	return link->lgr;
diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index 175026a..8134c15 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -1099,6 +1099,7 @@ int smc_llc_cli_add_link(struct smc_link *link, struct smc_llc_qentry *qentry)
 		goto out;
 out_clear_lnk:
 	lnk_new->state = SMC_LNK_INACTIVE;
+	smcr_lnk_cluster_on_lnk_state(lnk_new);
 	smcr_link_clear(lnk_new, false);
 out_reject:
 	smc_llc_cli_add_link_reject(qentry);
@@ -1278,6 +1279,7 @@ static void smc_llc_delete_asym_link(struct smc_link_group *lgr)
 		return; /* no asymmetric link */
 	if (!smc_link_downing(&lnk_asym->state))
 		return;
+	smcr_lnk_cluster_on_lnk_state(lnk_asym);
 	lnk_new = smc_switch_conns(lgr, lnk_asym, false);
 	smc_wr_tx_wait_no_pending_sends(lnk_asym);
 	if (!lnk_new)
@@ -1492,6 +1494,7 @@ int smc_llc_srv_add_link(struct smc_link *link,
 out_err:
 	if (link_new) {
 		link_new->state = SMC_LNK_INACTIVE;
+		smcr_lnk_cluster_on_lnk_state(link_new);
 		smcr_link_clear(link_new, false);
 	}
 out:
@@ -1602,8 +1605,10 @@ static void smc_llc_process_cli_delete_link(struct smc_link_group *lgr)
 	del_llc->reason = 0;
 	smc_llc_send_message(lnk, &qentry->msg); /* response */
 
-	if (smc_link_downing(&lnk_del->state))
+	if (smc_link_downing(&lnk_del->state)) {
+		smcr_lnk_cluster_on_lnk_state(lnk);
 		smc_switch_conns(lgr, lnk_del, false);
+	}
 	smcr_link_clear(lnk_del, true);
 
 	active_links = smc_llc_active_link_count(lgr);
@@ -1676,6 +1681,7 @@ static void smc_llc_process_srv_delete_link(struct smc_link_group *lgr)
 		goto out; /* asymmetric link already deleted */
 
 	if (smc_link_downing(&lnk_del->state)) {
+		smcr_lnk_cluster_on_lnk_state(lnk);
 		if (smc_switch_conns(lgr, lnk_del, false))
 			smc_wr_tx_wait_no_pending_sends(lnk_del);
 	}
@@ -2167,6 +2173,7 @@ void smc_llc_link_active(struct smc_link *link)
 		schedule_delayed_work(&link->llc_testlink_wrk,
 				      link->llc_testlink_time);
 	}
+	smcr_lnk_cluster_on_lnk_state(link);
 }
 
 /* called in worker context */
-- 
1.8.3.1

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