netdev - [PATCH net v2 3/3] s390/ism: Do not unregister clients with registered DMBs

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Date: Fri,  7 Jul 2023 12:56:22 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Paolo Abeni <pabeni@...hat.com>, Alexandra Winter <wintera@...ux.ibm.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>, Jan Karcher <jaka@...ux.ibm.com>,
        Stefan Raspl <raspl@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>
Cc: linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net v2 3/3] s390/ism: Do not unregister clients with registered DMBs

When ism_unregister_client() is called but the client still has DMBs
registered it returns -EBUSY and prints an error. This only happens
after the client has already been unregistered however. This is
unexpected as the unregister claims to have failed. Furthermore as this
implies a client bug a WARN() is more appropriate. Thus move the
deregistration after the check and use WARN().

Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration")
Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
---
 drivers/s390/net/ism_drv.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index 54091b7aea16..6df7f377d2f9 100644
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -96,29 +96,32 @@ int ism_unregister_client(struct ism_client *client)
 	int rc = 0;
 
 	mutex_lock(&ism_dev_list.mutex);
-	mutex_lock(&clients_lock);
-	clients[client->id] = NULL;
-	if (client->id + 1 == max_client)
-		max_client--;
-	mutex_unlock(&clients_lock);
 	list_for_each_entry(ism, &ism_dev_list.list, list) {
 		spin_lock_irqsave(&ism->lock, flags);
 		/* Stop forwarding IRQs and events */
 		ism->subs[client->id] = NULL;
 		for (int i = 0; i < ISM_NR_DMBS; ++i) {
 			if (ism->sba_client_arr[i] == client->id) {
-				pr_err("%s: attempt to unregister client '%s'"
-				       "with registered dmb(s)\n", __func__,
-				       client->name);
+				WARN(1, "%s: attempt to unregister '%s' with registered dmb(s)\n",
+				     __func__, client->name);
 				rc = -EBUSY;
-				goto out;
+				goto err_reg_dmb;
 			}
 		}
 		spin_unlock_irqrestore(&ism->lock, flags);
 	}
-out:
 	mutex_unlock(&ism_dev_list.mutex);
 
+	mutex_lock(&clients_lock);
+	clients[client->id] = NULL;
+	if (client->id + 1 == max_client)
+		max_client--;
+	mutex_unlock(&clients_lock);
+	return rc;
+
+err_reg_dmb:
+	spin_unlock_irqrestore(&ism->lock, flags);
+	mutex_unlock(&ism_dev_list.mutex);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(ism_unregister_client);
-- 
2.39.2