linux-kernel - [PATCH 02/11] nvmet-fcloop: add ref counting to lport

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Message-Id: <20250226-nvmet-fcloop-v1-2-c0bd83d43e6a@kernel.org>
Date: Wed, 26 Feb 2025 19:45:54 +0100
From: Daniel Wagner <wagi@...nel.org>
To: James Smart <james.smart@...adcom.com>, Christoph Hellwig <hch@....de>, 
 Sagi Grimberg <sagi@...mberg.me>, Chaitanya Kulkarni <kch@...dia.com>
Cc: Hannes Reinecke <hare@...e.de>, Keith Busch <kbusch@...nel.org>, 
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Daniel Wagner <wagi@...nel.org>
Subject: [PATCH 02/11] nvmet-fcloop: add ref counting to lport

The fcloop_lport objects live time is controlled by the user interface
add_local_port and del_local_port. nport, rport and tport objects are
pointing to the lport objects but here is no clear tracking. Let's
introduce an explicit ref counter for the lport objects and prepare the
stage for restructuring how lports are used.

Signed-off-by: Daniel Wagner <wagi@...nel.org>
---
 drivers/nvme/target/fcloop.c | 47 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 12 deletions(-)

diff --git a/drivers/nvme/target/fcloop.c b/drivers/nvme/target/fcloop.c
index 5493677a948d34391c7c08055dfefd91cc3ff33f..ca46830d46ecbaae21f3ee3e69aa7d52905abcae 100644
--- a/drivers/nvme/target/fcloop.c
+++ b/drivers/nvme/target/fcloop.c
@@ -208,6 +208,7 @@ struct fcloop_lport {
 	struct nvme_fc_local_port *localport;
 	struct list_head lport_list;
 	struct completion unreg_done;
+	struct kref ref;
 };
 
 struct fcloop_lport_priv {
@@ -1000,6 +1001,32 @@ fcloop_fcp_abort(struct nvme_fc_local_port *localport,
 	}
 }
 
+static void
+fcloop_lport_free(struct kref *ref)
+{
+	struct fcloop_lport *lport =
+		container_of(ref, struct fcloop_lport, ref);
+	unsigned long flags;
+
+	spin_lock_irqsave(&fcloop_lock, flags);
+	list_del(&lport->lport_list);
+	spin_unlock_irqrestore(&fcloop_lock, flags);
+
+	kfree(lport);
+}
+
+static void
+fcloop_lport_put(struct fcloop_lport *lport)
+{
+	kref_put(&lport->ref, fcloop_lport_free);
+}
+
+static int
+fcloop_lport_get(struct fcloop_lport *lport)
+{
+	return kref_get_unless_zero(&lport->ref);
+}
+
 static void
 fcloop_nport_free(struct kref *ref)
 {
@@ -1145,6 +1172,7 @@ fcloop_create_local_port(struct device *dev, struct device_attribute *attr,
 
 		lport->localport = localport;
 		INIT_LIST_HEAD(&lport->lport_list);
+		kref_init(&lport->ref);
 
 		spin_lock_irqsave(&fcloop_lock, flags);
 		list_add_tail(&lport->lport_list, &fcloop_lports);
@@ -1161,13 +1189,6 @@ fcloop_create_local_port(struct device *dev, struct device_attribute *attr,
 	return ret ? ret : count;
 }
 
-
-static void
-__unlink_local_port(struct fcloop_lport *lport)
-{
-	list_del(&lport->lport_list);
-}
-
 static int
 __wait_localport_unreg(struct fcloop_lport *lport)
 {
@@ -1180,7 +1201,7 @@ __wait_localport_unreg(struct fcloop_lport *lport)
 	if (!ret)
 		wait_for_completion(&lport->unreg_done);
 
-	kfree(lport);
+	fcloop_lport_put(lport);
 
 	return ret;
 }
@@ -1204,8 +1225,9 @@ fcloop_delete_local_port(struct device *dev, struct device_attribute *attr,
 	list_for_each_entry(tlport, &fcloop_lports, lport_list) {
 		if (tlport->localport->node_name == nodename &&
 		    tlport->localport->port_name == portname) {
+			if (!fcloop_lport_get(tlport))
+				break;
 			lport = tlport;
-			__unlink_local_port(lport);
 			break;
 		}
 	}
@@ -1215,6 +1237,7 @@ fcloop_delete_local_port(struct device *dev, struct device_attribute *attr,
 		return -ENOENT;
 
 	ret = __wait_localport_unreg(lport);
+	fcloop_lport_put(lport);
 
 	return ret ? ret : count;
 }
@@ -1640,17 +1663,17 @@ static void __exit fcloop_exit(void)
 	for (;;) {
 		lport = list_first_entry_or_null(&fcloop_lports,
 						typeof(*lport), lport_list);
-		if (!lport)
+		if (!lport || !fcloop_lport_get(lport))
 			break;
 
-		__unlink_local_port(lport);
-
 		spin_unlock_irqrestore(&fcloop_lock, flags);
 
 		ret = __wait_localport_unreg(lport);
 		if (ret)
 			pr_warn("%s: Failed deleting local port\n", __func__);
 
+		fcloop_lport_put(lport);
+
 		spin_lock_irqsave(&fcloop_lock, flags);
 	}
 

-- 
2.48.1