[PATCH net-next 1/3] net/smc: refactoring lgr pending lock

["D. Wythe" <alibuda@linux.alibaba.com>]

This patch replaces the locking and unlocking of lgr pending with
a unified inline function, and since the granularity of lgr pending
lock is within the lifecycle of init_info, which make it possible
to record the lock state on init_info, which provides a potential
functionality for multiple unlocks without triggering exceptions, which
creates conditions to reduce the scope of locks in the future.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
 net/smc/af_smc.c   | 24 ++++++++++++------------
 net/smc/smc_core.h | 29 +++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 9d76e902fd77..19480d8affb0 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1251,10 +1251,10 @@ static int smc_connect_rdma(struct smc_sock *smc,
 	if (reason_code)
 		return reason_code;
 
-	mutex_lock(&smc_client_lgr_pending);
+	smc_lgr_pending_lock(ini, &smc_client_lgr_pending);
 	reason_code = smc_conn_create(smc, ini);
 	if (reason_code) {
-		mutex_unlock(&smc_client_lgr_pending);
+		smc_lgr_pending_unlock(ini);
 		return reason_code;
 	}
 
@@ -1343,7 +1343,7 @@ static int smc_connect_rdma(struct smc_sock *smc,
 		if (reason_code)
 			goto connect_abort;
 	}
-	mutex_unlock(&smc_client_lgr_pending);
+	smc_lgr_pending_unlock(ini);
 
 	smc_copy_sock_settings_to_clc(smc);
 	smc->connect_nonblock = 0;
@@ -1353,7 +1353,7 @@ 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_lgr_pending_unlock(ini);
 	smc->connect_nonblock = 0;
 
 	return reason_code;
@@ -1412,10 +1412,10 @@ static int smc_connect_ism(struct smc_sock *smc,
 	ini->ism_peer_gid[ini->ism_selected].gid = ntohll(aclc->d0.gid);
 
 	/* there is only one lgr role for SMC-D; use server lock */
-	mutex_lock(&smc_server_lgr_pending);
+	smc_lgr_pending_lock(ini, &smc_server_lgr_pending);
 	rc = smc_conn_create(smc, ini);
 	if (rc) {
-		mutex_unlock(&smc_server_lgr_pending);
+		smc_lgr_pending_unlock(ini);
 		return rc;
 	}
 
@@ -1446,7 +1446,7 @@ static int smc_connect_ism(struct smc_sock *smc,
 				  aclc->hdr.version, eid, ini);
 	if (rc)
 		goto connect_abort;
-	mutex_unlock(&smc_server_lgr_pending);
+	smc_lgr_pending_unlock(ini);
 
 	smc_copy_sock_settings_to_clc(smc);
 	smc->connect_nonblock = 0;
@@ -1456,7 +1456,7 @@ static int smc_connect_ism(struct smc_sock *smc,
 	return 0;
 connect_abort:
 	smc_conn_abort(smc, ini->first_contact_local);
-	mutex_unlock(&smc_server_lgr_pending);
+	smc_lgr_pending_unlock(ini);
 	smc->connect_nonblock = 0;
 
 	return rc;
@@ -2478,7 +2478,7 @@ static void smc_listen_work(struct work_struct *work)
 	if (rc)
 		goto out_decl;
 
-	mutex_lock(&smc_server_lgr_pending);
+	smc_lgr_pending_lock(ini, &smc_server_lgr_pending);
 	smc_close_init(new_smc);
 	smc_rx_init(new_smc);
 	smc_tx_init(new_smc);
@@ -2497,7 +2497,7 @@ static void smc_listen_work(struct work_struct *work)
 
 	/* SMC-D does not need this lock any more */
 	if (ini->is_smcd)
-		mutex_unlock(&smc_server_lgr_pending);
+		smc_lgr_pending_unlock(ini);
 
 	/* receive SMC Confirm CLC message */
 	memset(buf, 0, sizeof(*buf));
@@ -2528,7 +2528,7 @@ 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_lgr_pending_unlock(ini);
 	}
 	smc_conn_save_peer_info(new_smc, cclc);
 
@@ -2544,7 +2544,7 @@ static void smc_listen_work(struct work_struct *work)
 	goto out_free;
 
 out_unlock:
-	mutex_unlock(&smc_server_lgr_pending);
+	smc_lgr_pending_unlock(ini);
 out_decl:
 	smc_listen_decline(new_smc, rc, ini ? ini->first_contact_local : 0,
 			   proposal_version);
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 69b54ecd6503..5abe9438772c 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -432,6 +432,8 @@ struct smc_init_info {
 	u8			ism_offered_cnt; /* # of ISM devices offered */
 	u8			ism_selected;    /* index of selected ISM dev*/
 	u8			smcd_version;
+	/* mutex holding for conn create */
+	struct mutex *mutex;
 };
 
 /* Find the connection associated with the given alert token in the link group.
@@ -600,6 +602,33 @@ int smcr_nl_get_lgr(struct sk_buff *skb, struct netlink_callback *cb);
 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);
 
+static inline void smc_lgr_pending_lock(struct smc_init_info *ini, struct mutex *lock)
+{
+	if (unlikely(ini->mutex))
+		pr_warn_once("smc: lgr pending deadlock dected.");
+
+	mutex_lock(lock);
+	ini->mutex = lock;
+}
+
+/* It will save the locking status of the ini, which provides a potential functionality
+ * for multiple unlocks without triggering exceptions. This creates conditions
+ * to reduce the scope of locks in the future.
+ */
+static inline void smc_lgr_pending_unlock(struct smc_init_info *ini)
+{
+	/* tempory */
+	struct mutex *lock;
+
+	/* already unlock it, just return */
+	if (!ini->mutex)
+		return;
+
+	lock = ini->mutex;
+	ini->mutex = NULL;
+	mutex_unlock(lock);
+}
+
 static inline struct smc_link_group *smc_get_lgr(struct smc_link *link)
 {
 	return link->lgr;
-- 
2.45.0