[PATCH net-next 5/7] net/smc: use client and server LGR pending locks for SMC-R

[Ursula Braun <ubraun@linux.ibm.com>]

From: Hans Wippel <hwippel@linux.ibm.com>

If SMC client and server connections are both established at the same
time, smc_connect_rdma() cannot send a CLC confirm message while
smc_listen_work() is waiting for one due to lock contention. This can
result in timeouts in smc_clc_wait_msg() and failed SMC connections.

In case of SMC-R, there are two types of LGRs (client and server LGRs)
which can be protected by separate locks. So, this patch splits the LGR
pending lock into two separate locks for client and server to avoid the
locking issue for SMC-R.

Signed-off-by: Hans Wippel <hwippel@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
---
 net/smc/af_smc.c | 44 ++++++++++++++++++++++++++++----------------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index cf49ed05007b..48ea7669161f 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -42,8 +42,11 @@
 #include "smc_rx.h"
 #include "smc_close.h"
 
-static DEFINE_MUTEX(smc_create_lgr_pending);	/* serialize link group
-						 * creation
+static DEFINE_MUTEX(smc_server_lgr_pending);	/* serialize link group
+						 * creation on server
+						 */
+static DEFINE_MUTEX(smc_client_lgr_pending);	/* serialize link group
+						 * creation on client
 						 */
 
 static void smc_tcp_listen_work(struct work_struct *);
@@ -477,7 +480,12 @@ static int smc_connect_abort(struct smc_sock *smc, int reason_code,
 {
 	if (local_contact == SMC_FIRST_CONTACT)
 		smc_lgr_forget(smc->conn.lgr);
-	mutex_unlock(&smc_create_lgr_pending);
+	if (smc->conn.lgr->is_smcd)
+		/* there is only one lgr role for SMC-D; use server lock */
+		mutex_unlock(&smc_server_lgr_pending);
+	else
+		mutex_unlock(&smc_client_lgr_pending);
+
 	smc_conn_free(&smc->conn);
 	return reason_code;
 }
@@ -562,7 +570,7 @@ static int smc_connect_rdma(struct smc_sock *smc,
 	struct smc_link *link;
 	int reason_code = 0;
 
-	mutex_lock(&smc_create_lgr_pending);
+	mutex_lock(&smc_client_lgr_pending);
 	local_contact = smc_conn_create(smc, false, aclc->hdr.flag, ibdev,
 					ibport, ntoh24(aclc->qpn), &aclc->lcl,
 					NULL, 0);
@@ -573,7 +581,8 @@ static int smc_connect_rdma(struct smc_sock *smc,
 			reason_code = SMC_CLC_DECL_SYNCERR; /* synchr. error */
 		else
 			reason_code = SMC_CLC_DECL_INTERR; /* other error */
-		return smc_connect_abort(smc, reason_code, 0);
+		mutex_unlock(&smc_client_lgr_pending);
+		return reason_code;
 	}
 	link = &smc->conn.lgr->lnk[SMC_SINGLE_LINK];
 
@@ -617,7 +626,7 @@ static int smc_connect_rdma(struct smc_sock *smc,
 			return smc_connect_abort(smc, reason_code,
 						 local_contact);
 	}
-	mutex_unlock(&smc_create_lgr_pending);
+	mutex_unlock(&smc_client_lgr_pending);
 
 	smc_copy_sock_settings_to_clc(smc);
 	if (smc->sk.sk_state == SMC_INIT)
@@ -634,11 +643,14 @@ static int smc_connect_ism(struct smc_sock *smc,
 	int local_contact = SMC_FIRST_CONTACT;
 	int rc = 0;
 
-	mutex_lock(&smc_create_lgr_pending);
+	/* there is only one lgr role for SMC-D; use server lock */
+	mutex_lock(&smc_server_lgr_pending);
 	local_contact = smc_conn_create(smc, true, aclc->hdr.flag, NULL, 0, 0,
 					NULL, ismdev, aclc->gid);
-	if (local_contact < 0)
-		return smc_connect_abort(smc, SMC_CLC_DECL_MEM, 0);
+	if (local_contact < 0) {
+		mutex_unlock(&smc_server_lgr_pending);
+		return SMC_CLC_DECL_MEM;
+	}
 
 	/* Create send and receive buffers */
 	if (smc_buf_create(smc, true))
@@ -652,7 +664,7 @@ static int smc_connect_ism(struct smc_sock *smc,
 	rc = smc_clc_send_confirm(smc);
 	if (rc)
 		return smc_connect_abort(smc, rc, local_contact);
-	mutex_unlock(&smc_create_lgr_pending);
+	mutex_unlock(&smc_server_lgr_pending);
 
 	smc_copy_sock_settings_to_clc(smc);
 	if (smc->sk.sk_state == SMC_INIT)
@@ -1251,7 +1263,7 @@ static void smc_listen_work(struct work_struct *work)
 		return;
 	}
 
-	mutex_lock(&smc_create_lgr_pending);
+	mutex_lock(&smc_server_lgr_pending);
 	smc_close_init(new_smc);
 	smc_rx_init(new_smc);
 	smc_tx_init(new_smc);
@@ -1273,7 +1285,7 @@ static void smc_listen_work(struct work_struct *work)
 				  &local_contact) ||
 	     smc_listen_rdma_reg(new_smc, local_contact))) {
 		/* SMC not supported, decline */
-		mutex_unlock(&smc_create_lgr_pending);
+		mutex_unlock(&smc_server_lgr_pending);
 		smc_listen_decline(new_smc, SMC_CLC_DECL_MODEUNSUPP,
 				   local_contact);
 		return;
@@ -1282,21 +1294,21 @@ static void smc_listen_work(struct work_struct *work)
 	/* send SMC Accept CLC message */
 	rc = smc_clc_send_accept(new_smc, local_contact);
 	if (rc) {
-		mutex_unlock(&smc_create_lgr_pending);
+		mutex_unlock(&smc_server_lgr_pending);
 		smc_listen_decline(new_smc, rc, local_contact);
 		return;
 	}
 
 	/* SMC-D does not need this lock any more */
 	if (ism_supported)
-		mutex_unlock(&smc_create_lgr_pending);
+		mutex_unlock(&smc_server_lgr_pending);
 
 	/* receive SMC Confirm CLC message */
 	reason_code = smc_clc_wait_msg(new_smc, &cclc, sizeof(cclc),
 				       SMC_CLC_CONFIRM, CLC_WAIT_TIME);
 	if (reason_code) {
 		if (!ism_supported)
-			mutex_unlock(&smc_create_lgr_pending);
+			mutex_unlock(&smc_server_lgr_pending);
 		smc_listen_decline(new_smc, reason_code, local_contact);
 		return;
 	}
@@ -1304,7 +1316,7 @@ static void smc_listen_work(struct work_struct *work)
 	/* finish worker */
 	if (!ism_supported) {
 		rc = smc_listen_rdma_finish(new_smc, &cclc, local_contact);
-		mutex_unlock(&smc_create_lgr_pending);
+		mutex_unlock(&smc_server_lgr_pending);
 		if (rc)
 			return;
 	}
-- 
2.16.4