netdev - [PATCH net 6/9] net/smc: longer delay for client link group removal

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Date:   Thu, 21 Sep 2017 09:16:31 +0200
From:   Ursula Braun <ubraun@...ux.vnet.ibm.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-s390@...r.kernel.org, jwi@...ux.vnet.ibm.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        raspl@...ux.vnet.ibm.com, ubraun@...ux.vnet.ibm.com
Subject: [PATCH net 6/9] net/smc: longer delay for client link group removal

Client link group creation always follows the server linkgroup creation.
If peer creates a new server link group, client has to create a new
client link group. If peer reuses a server link group for a new
connection, client has to reuse its client link group as well. This
patch introduces a longer delay for client link group removal to make
sure this link group still exists, once the peer decides to reuse a
server link group. This avoids out-of-sync conditions for link groups.
If already scheduled, modify the delay.

Signed-off-by: Ursula Braun <ubraun@...ux.vnet.ibm.com>
---
 net/smc/smc_core.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 1a16d51e2330..20b66e79c5d6 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -25,8 +25,9 @@
 #include "smc_cdc.h"
 #include "smc_close.h"
 
-#define SMC_LGR_NUM_INCR	256
-#define SMC_LGR_FREE_DELAY	(600 * HZ)
+#define SMC_LGR_NUM_INCR		256
+#define SMC_LGR_FREE_DELAY_SERV		(600 * HZ)
+#define SMC_LGR_FREE_DELAY_CLNT		(SMC_LGR_FREE_DELAY_SERV + 10)
 
 static u32 smc_lgr_num;			/* unique link group number */
 
@@ -107,8 +108,15 @@ static void smc_lgr_unregister_conn(struct smc_connection *conn)
 		__smc_lgr_unregister_conn(conn);
 	}
 	write_unlock_bh(&lgr->conns_lock);
-	if (reduced && !lgr->conns_num)
-		schedule_delayed_work(&lgr->free_work, SMC_LGR_FREE_DELAY);
+	if (!reduced || lgr->conns_num)
+		return;
+	/* client link group creation always follows the server link group
+	 * creation. For client use a somewhat higher removal delay time,
+	 * otherwise there is a risk of out-of-sync link groups.
+	 */
+	mod_delayed_work(system_wq, &lgr->free_work,
+			 lgr->role == SMC_CLNT ? SMC_LGR_FREE_DELAY_CLNT :
+						 SMC_LGR_FREE_DELAY_SERV);
 }
 
 static void smc_lgr_free_work(struct work_struct *work)
-- 
2.13.5