netdev - [PATCH 3/4] net: initialize online_mask unconditionally in __netif_set_xps

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Date:   Sun,  2 Oct 2022 08:17:01 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Menglong Dong <imagedong@...cent.com>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Petr Machata <petrm@...dia.com>, linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH 3/4] net: initialize online_mask unconditionally in __netif_set_xps_queue()

If the mask is initialized unconditionally, it's possible to use bitmap
API to traverse it, which is done in the following patch.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 net/core/dev.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 39a4cc7b3a06..266378ad1cf1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2542,7 +2542,7 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 			  u16 index, enum xps_map_type type)
 {
 	struct xps_dev_maps *dev_maps, *new_dev_maps = NULL, *old_dev_maps = NULL;
-	const unsigned long *online_mask = NULL;
+	const unsigned long *online_mask;
 	bool active = false, copy = false;
 	int i, j, tci, numa_node_id = -2;
 	int maps_sz, num_tc = 1, tc = 0;
@@ -2565,9 +2565,11 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 
 	if (type == XPS_RXQS) {
 		nr_ids = dev->num_rx_queues;
+		online_mask = bitmap_alloc(nr_ids, GFP_KERNEL);
+		if (!online_mask)
+			return -ENOMEM;
 	} else {
-		if (num_possible_cpus() > 1)
-			online_mask = cpumask_bits(cpu_online_mask);
+		online_mask = cpumask_bits(cpu_online_mask);
 		nr_ids = nr_cpu_ids;
 	}
 
@@ -2593,10 +2595,8 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 	     j < nr_ids;) {
 		if (!new_dev_maps) {
 			new_dev_maps = kzalloc(maps_sz, GFP_KERNEL);
-			if (!new_dev_maps) {
-				mutex_unlock(&xps_map_mutex);
-				return -ENOMEM;
-			}
+			if (!new_dev_maps)
+				goto err_out;
 
 			new_dev_maps->nr_ids = nr_ids;
 			new_dev_maps->num_tc = num_tc;
@@ -2718,7 +2718,8 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 
 out_no_maps:
 	mutex_unlock(&xps_map_mutex);
-
+	if (type == XPS_RXQS)
+		bitmap_free(online_mask);
 	return 0;
 error:
 	/* remove any maps that we added */
@@ -2733,8 +2734,10 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 		}
 	}
 
+err_out:
 	mutex_unlock(&xps_map_mutex);
-
+	if (type == XPS_RXQS)
+		bitmap_free(online_mask);
 	kfree(new_dev_maps);
 	return -ENOMEM;
 }
-- 
2.34.1