net/smc: improve link group freeing

Usually link groups are freed delayed to enable quick connection
creation for a follow-on SMC socket. Terminated link groups are
freed faster. This patch makes sure, fast schedule of link group
freeing is not rescheduled by a delayed schedule. And it makes sure
link group freeing is not rescheduled, if the real freeing is already
running.
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

net/smc/smc_core.c

@@ -61,14 +61,21 @@ static void smc_lgr_schedule_free_work(struct smc_link_group *lgr)
 	 * 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->is_smcd && lgr->role == SMC_CLNT) ?
-			 SMC_LGR_FREE_DELAY_CLNT : SMC_LGR_FREE_DELAY_SERV);
+	if (!lgr->freeing && !lgr->freefast) {
+		mod_delayed_work(system_wq, &lgr->free_work,
+				 (!lgr->is_smcd && lgr->role == SMC_CLNT) ?
+						SMC_LGR_FREE_DELAY_CLNT :
+						SMC_LGR_FREE_DELAY_SERV);
+	}
 }
 
 void smc_lgr_schedule_free_work_fast(struct smc_link_group *lgr)
 {
-	mod_delayed_work(system_wq, &lgr->free_work, SMC_LGR_FREE_DELAY_FAST);
+	if (!lgr->freeing && !lgr->freefast) {
+		lgr->freefast = 1;
+		mod_delayed_work(system_wq, &lgr->free_work,
+				 SMC_LGR_FREE_DELAY_FAST);
+	}
 }
 
 /* Register connection's alert token in our lookup structure.
@@ -171,10 +178,15 @@ static void smc_lgr_free_work(struct work_struct *work)
 						  struct smc_link_group,
 						  free_work);
 	spinlock_t *lgr_lock;
+	struct smc_link *lnk;
 	bool conns;
 
 	smc_lgr_list_head(lgr, &lgr_lock);
 	spin_lock_bh(lgr_lock);
+	if (lgr->freeing) {
+		spin_unlock_bh(lgr_lock);
+		return;
+	}
 	read_lock_bh(&lgr->conns_lock);
 	conns = RB_EMPTY_ROOT(&lgr->conns_all);
 	read_unlock_bh(&lgr->conns_lock);
@@ -183,29 +195,27 @@ static void smc_lgr_free_work(struct work_struct *work)
 		return;
 	}
 	list_del_init(&lgr->list); /* remove from smc_lgr_list */
-	spin_unlock_bh(lgr_lock);
 
+	lnk = &lgr->lnk[SMC_SINGLE_LINK];
 	if (!lgr->is_smcd && !lgr->terminating)	{
-		struct smc_link *lnk = &lgr->lnk[SMC_SINGLE_LINK];
-
 		/* try to send del link msg, on error free lgr immediately */
 		if (lnk->state == SMC_LNK_ACTIVE &&
 		    !smc_link_send_delete(lnk)) {
 			/* reschedule in case we never receive a response */
 			smc_lgr_schedule_free_work(lgr);
+			spin_unlock_bh(lgr_lock);
 			return;
 		}
 	}
+	lgr->freeing = 1; /* this instance does the freeing, no new schedule */
+	spin_unlock_bh(lgr_lock);
+	cancel_delayed_work(&lgr->free_work);
 
-	if (!delayed_work_pending(&lgr->free_work)) {
-		struct smc_link *lnk = &lgr->lnk[SMC_SINGLE_LINK];
-
-		if (!lgr->is_smcd && lnk->state != SMC_LNK_INACTIVE)
-			smc_llc_link_inactive(lnk);
-		if (lgr->is_smcd)
-			smc_ism_signal_shutdown(lgr);
-		smc_lgr_free(lgr);
-	}
+	if (!lgr->is_smcd && lnk->state != SMC_LNK_INACTIVE)
+		smc_llc_link_inactive(lnk);
+	if (lgr->is_smcd)
+		smc_ism_signal_shutdown(lgr);
+	smc_lgr_free(lgr);
 }
 
 /* create a new SMC link group */
@@ -233,6 +243,9 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini)
 	}
 	lgr->is_smcd = ini->is_smcd;
 	lgr->sync_err = 0;
+	lgr->terminating = 0;
+	lgr->freefast = 0;
+	lgr->freeing = 0;
 	lgr->vlan_id = ini->vlan_id;
 	rwlock_init(&lgr->sndbufs_lock);
 	rwlock_init(&lgr->rmbs_lock);
@@ -513,7 +526,7 @@ static void __smc_lgr_terminate(struct smc_link_group *lgr)
 	read_unlock_bh(&lgr->conns_lock);
 	if (!lgr->is_smcd)
 		wake_up(&lgr->lnk[SMC_SINGLE_LINK].wr_reg_wait);
-	smc_lgr_schedule_free_work(lgr);
+	smc_lgr_schedule_free_work_fast(lgr);
 }
 
 /* unlink and terminate link group */

net/smc/smc_core.h

@@ -204,6 +204,8 @@ struct smc_link_group {
 	struct delayed_work	free_work;	/* delayed freeing of an lgr */
 	u8			sync_err : 1;	/* lgr no longer fits to peer */
 	u8			terminating : 1;/* lgr is terminating */
+	u8			freefast : 1;	/* free worker scheduled fast */
+	u8			freeing : 1;	/* lgr is being freed */
 
 	bool			is_smcd;	/* SMC-R or SMC-D */
 	union {