net/smc: llc_conf_mutex refactor, replace it with rw_semaphore

llc_conf_mutex was used to protect links and link related configurations
in the same link group, for example, add or delete links. However,
in most cases, the protected critical area has only read semantics and
with no write semantics at all, such as obtaining a usable link or an
available rmb_desc.

This patch do simply code refactoring, replace mutex with rw_semaphore,
replace mutex_lock with down_write and replace mutex_unlock with
up_write.

Theoretically, this replacement is equivalent, but after this patch,
we can distinguish lock granularity according to different semantics
of critical areas.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 9 deletions

diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index 524649d0ab65..c0e73e436e98 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -1202,12 +1202,12 @@ static void smc_llc_process_cli_add_link(struct smc_link_group *lgr)
 
 	qentry = smc_llc_flow_qentry_clr(&lgr->llc_flow_lcl);
 
-	mutex_lock(&lgr->llc_conf_mutex);
+	down_write(&lgr->llc_conf_mutex);
 	if (smc_llc_is_local_add_link(&qentry->msg))
 		smc_llc_cli_add_link_invite(qentry->link, qentry);
 	else
 		smc_llc_cli_add_link(qentry->link, qentry);
-	mutex_unlock(&lgr->llc_conf_mutex);
+	up_write(&lgr->llc_conf_mutex);
 }
 
 static int smc_llc_active_link_count(struct smc_link_group *lgr)
@@ -1509,13 +1509,13 @@ static void smc_llc_process_srv_add_link(struct smc_link_group *lgr)
 
 	qentry = smc_llc_flow_qentry_clr(&lgr->llc_flow_lcl);
 
-	mutex_lock(&lgr->llc_conf_mutex);
+	down_write(&lgr->llc_conf_mutex);
 	rc = smc_llc_srv_add_link(link, qentry);
 	if (!rc && lgr->type == SMC_LGR_SYMMETRIC) {
 		/* delete any asymmetric link */
 		smc_llc_delete_asym_link(lgr);
 	}
-	mutex_unlock(&lgr->llc_conf_mutex);
+	up_write(&lgr->llc_conf_mutex);
 	kfree(qentry);
 }
 
@@ -1582,7 +1582,7 @@ static void smc_llc_process_cli_delete_link(struct smc_link_group *lgr)
 		smc_lgr_terminate_sched(lgr);
 		goto out;
 	}
-	mutex_lock(&lgr->llc_conf_mutex);
+	down_write(&lgr->llc_conf_mutex);
 	/* delete single link */
 	for (lnk_idx = 0; lnk_idx < SMC_LINKS_PER_LGR_MAX; lnk_idx++) {
 		if (lgr->lnk[lnk_idx].link_id != del_llc->link_num)
@@ -1616,7 +1616,7 @@ static void smc_llc_process_cli_delete_link(struct smc_link_group *lgr)
 		smc_lgr_terminate_sched(lgr);
 	}
 out_unlock:
-	mutex_unlock(&lgr->llc_conf_mutex);
+	up_write(&lgr->llc_conf_mutex);
 out:
 	kfree(qentry);
 }
@@ -1652,7 +1652,7 @@ static void smc_llc_process_srv_delete_link(struct smc_link_group *lgr)
 	int active_links;
 	int i;
 
-	mutex_lock(&lgr->llc_conf_mutex);
+	down_write(&lgr->llc_conf_mutex);
 	qentry = smc_llc_flow_qentry_clr(&lgr->llc_flow_lcl);
 	lnk = qentry->link;
 	del_llc = &qentry->msg.delete_link;
@@ -1708,7 +1708,7 @@ static void smc_llc_process_srv_delete_link(struct smc_link_group *lgr)
 		smc_llc_add_link_local(lnk);
 	}
 out:
-	mutex_unlock(&lgr->llc_conf_mutex);
+	up_write(&lgr->llc_conf_mutex);
 	kfree(qentry);
 }
 
@@ -2126,7 +2126,7 @@ void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
 	spin_lock_init(&lgr->llc_flow_lock);
 	init_waitqueue_head(&lgr->llc_flow_waiter);
 	init_waitqueue_head(&lgr->llc_msg_waiter);
-	mutex_init(&lgr->llc_conf_mutex);
+	init_rwsem(&lgr->llc_conf_mutex);
 	lgr->llc_testlink_time = READ_ONCE(net->smc.sysctl_smcr_testlink_time);
 }