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Date:   Thu, 24 Dec 2020 13:05:40 +0200
From:   leonid.ravich@...l.com
To:     james.smart@...adcom.com
Cc:     lravich@...il.com, Leonid Ravich <Leonid.Ravich@...l.com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] nvmet-fc: associations list replaced with hlist rcu,

From: Leonid Ravich <Leonid.Ravich@....com>

to remove locking from nvmet_fc_find_target_queue
which called per IO.

Signed-off-by: Leonid Ravich <Leonid.Ravich@....com>
---
 drivers/nvme/target/fc.c | 54 ++++++++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 22 deletions(-)

diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index cd4e73aa9807..3928a17d073c 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -105,7 +105,7 @@ struct nvmet_fc_tgtport {
 	struct list_head		ls_rcv_list;
 	struct list_head		ls_req_list;
 	struct list_head		ls_busylist;
-	struct list_head		assoc_list;
+	struct hlist_head		assoc_list;
 	struct list_head		host_list;
 	struct ida			assoc_cnt;
 	struct nvmet_fc_port_entry	*pe;
@@ -163,10 +163,11 @@ struct nvmet_fc_tgt_assoc {
 	struct nvmet_fc_tgtport		*tgtport;
 	struct nvmet_fc_hostport	*hostport;
 	struct nvmet_fc_ls_iod		*rcv_disconn;
-	struct list_head		a_list;
+	struct hlist_node		a_list;
 	struct nvmet_fc_tgt_queue	*queues[NVMET_NR_QUEUES + 1];
 	struct kref			ref;
 	struct work_struct		del_work;
+	struct rcu_head		rcu_head;
 };
 
 
@@ -965,24 +966,23 @@ nvmet_fc_find_target_queue(struct nvmet_fc_tgtport *tgtport,
 	struct nvmet_fc_tgt_queue *queue;
 	u64 association_id = nvmet_fc_getassociationid(connection_id);
 	u16 qid = nvmet_fc_getqueueid(connection_id);
-	unsigned long flags;
 
 	if (qid > NVMET_NR_QUEUES)
 		return NULL;
 
-	spin_lock_irqsave(&tgtport->lock, flags);
-	list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(assoc, &tgtport->assoc_list, a_list) {
 		if (association_id == assoc->association_id) {
 			queue = assoc->queues[qid];
 			if (queue &&
 			    (!atomic_read(&queue->connected) ||
 			     !nvmet_fc_tgt_q_get(queue)))
 				queue = NULL;
-			spin_unlock_irqrestore(&tgtport->lock, flags);
+			rcu_read_unlock();
 			return queue;
 		}
 	}
-	spin_unlock_irqrestore(&tgtport->lock, flags);
+	rcu_read_unlock();
 	return NULL;
 }
 
@@ -1118,7 +1118,7 @@ nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle)
 
 	assoc->tgtport = tgtport;
 	assoc->a_id = idx;
-	INIT_LIST_HEAD(&assoc->a_list);
+	INIT_HLIST_NODE(&assoc->a_list);
 	kref_init(&assoc->ref);
 	INIT_WORK(&assoc->del_work, nvmet_fc_delete_assoc);
 	atomic_set(&assoc->terminating, 0);
@@ -1129,7 +1129,7 @@ nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle)
 
 		spin_lock_irqsave(&tgtport->lock, flags);
 		needrandom = false;
-		list_for_each_entry(tmpassoc, &tgtport->assoc_list, a_list) {
+		hlist_for_each_entry(tmpassoc, &tgtport->assoc_list, a_list) {
 			if (ran == tmpassoc->association_id) {
 				needrandom = true;
 				break;
@@ -1137,7 +1137,7 @@ nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle)
 		}
 		if (!needrandom) {
 			assoc->association_id = ran;
-			list_add_tail(&assoc->a_list, &tgtport->assoc_list);
+			hlist_add_tail_rcu(&assoc->a_list, &tgtport->assoc_list);
 		}
 		spin_unlock_irqrestore(&tgtport->lock, flags);
 	}
@@ -1153,6 +1153,17 @@ nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle)
 	return NULL;
 }
 
+void nvmet_assoc_free_queue_rcu(struct rcu_head *rcu_head) {
+	struct nvmet_fc_tgt_assoc *assoc =
+		container_of(rcu_head, struct nvmet_fc_tgt_assoc, rcu_head);
+	struct nvmet_fc_tgtport *tgtport = assoc->tgtport;
+
+	kfree(assoc);
+	dev_info(tgtport->dev,
+		"{%d:%d} Association freed\n",
+		tgtport->fc_target_port.port_num, assoc->a_id);
+}
+
 static void
 nvmet_fc_target_assoc_free(struct kref *ref)
 {
@@ -1167,17 +1178,14 @@ nvmet_fc_target_assoc_free(struct kref *ref)
 
 	nvmet_fc_free_hostport(assoc->hostport);
 	spin_lock_irqsave(&tgtport->lock, flags);
-	list_del(&assoc->a_list);
+	hlist_del_rcu(&assoc->a_list);
 	oldls = assoc->rcv_disconn;
 	spin_unlock_irqrestore(&tgtport->lock, flags);
 	/* if pending Rcv Disconnect Association LS, send rsp now */
 	if (oldls)
 		nvmet_fc_xmt_ls_rsp(tgtport, oldls);
 	ida_simple_remove(&tgtport->assoc_cnt, assoc->a_id);
-	dev_info(tgtport->dev,
-		"{%d:%d} Association freed\n",
-		tgtport->fc_target_port.port_num, assoc->a_id);
-	kfree(assoc);
+	call_rcu(&assoc->rcu_head, nvmet_assoc_free_queue_rcu);
 	nvmet_fc_tgtport_put(tgtport);
 }
 
@@ -1237,7 +1245,7 @@ nvmet_fc_find_target_assoc(struct nvmet_fc_tgtport *tgtport,
 	unsigned long flags;
 
 	spin_lock_irqsave(&tgtport->lock, flags);
-	list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
+	hlist_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
 		if (association_id == assoc->association_id) {
 			ret = assoc;
 			if (!nvmet_fc_tgt_a_get(assoc))
@@ -1397,7 +1405,7 @@ nvmet_fc_register_targetport(struct nvmet_fc_port_info *pinfo,
 	INIT_LIST_HEAD(&newrec->ls_rcv_list);
 	INIT_LIST_HEAD(&newrec->ls_req_list);
 	INIT_LIST_HEAD(&newrec->ls_busylist);
-	INIT_LIST_HEAD(&newrec->assoc_list);
+	INIT_HLIST_HEAD(&newrec->assoc_list);
 	INIT_LIST_HEAD(&newrec->host_list);
 	kref_init(&newrec->ref);
 	ida_init(&newrec->assoc_cnt);
@@ -1473,11 +1481,12 @@ nvmet_fc_tgtport_get(struct nvmet_fc_tgtport *tgtport)
 static void
 __nvmet_fc_free_assocs(struct nvmet_fc_tgtport *tgtport)
 {
-	struct nvmet_fc_tgt_assoc *assoc, *next;
+	struct nvmet_fc_tgt_assoc *assoc;
+	struct hlist_node *next;
 	unsigned long flags;
 
 	spin_lock_irqsave(&tgtport->lock, flags);
-	list_for_each_entry_safe(assoc, next,
+	hlist_for_each_entry_safe(assoc, next,
 				&tgtport->assoc_list, a_list) {
 		if (!nvmet_fc_tgt_a_get(assoc))
 			continue;
@@ -1522,12 +1531,13 @@ nvmet_fc_invalidate_host(struct nvmet_fc_target_port *target_port,
 			void *hosthandle)
 {
 	struct nvmet_fc_tgtport *tgtport = targetport_to_tgtport(target_port);
-	struct nvmet_fc_tgt_assoc *assoc, *next;
+	struct nvmet_fc_tgt_assoc *assoc;
+	struct hlist_node *next;
 	unsigned long flags;
 	bool noassoc = true;
 
 	spin_lock_irqsave(&tgtport->lock, flags);
-	list_for_each_entry_safe(assoc, next,
+	hlist_for_each_entry_safe(assoc, next,
 				&tgtport->assoc_list, a_list) {
 		if (!assoc->hostport ||
 		    assoc->hostport->hosthandle != hosthandle)
@@ -1569,7 +1579,7 @@ nvmet_fc_delete_ctrl(struct nvmet_ctrl *ctrl)
 		spin_unlock_irqrestore(&nvmet_fc_tgtlock, flags);
 
 		spin_lock_irqsave(&tgtport->lock, flags);
-		list_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
+		hlist_for_each_entry(assoc, &tgtport->assoc_list, a_list) {
 			queue = assoc->queues[0];
 			if (queue && queue->nvme_sq.ctrl == ctrl) {
 				if (nvmet_fc_tgt_a_get(assoc))
-- 
2.16.2

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