netdev - [PATCH] dql: Fix dql->limit value when reset.

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Message-ID: <Z9qHD1s/NEuQBdgH@pilot-ThinkCentre-M930t-N000>
Date: Wed, 19 Mar 2025 16:57:51 +0800
From: Jing Su <jingsusu@...iglobal.com>
To: <edumazet@...gle.com>, <pabeni@...hat.com>, <kuba@...nel.org>,
	<davem@...emloft.net>, <horms@...nel.org>
CC: <netdev@...r.kernel.org>, <jingsusu@...iglobal.com>,
	<jinnasujing@...il.com>
Subject: [PATCH] dql: Fix dql->limit value when reset.

Executing dql_reset after setting a non-zero value for limit_min can
lead to an unreasonable situation where dql->limit is less than
dql->limit_min.

For instance, after setting
/sys/class/net/eth*/queues/tx-0/byte_queue_limits/limit_min,
an ifconfig down/up operation might cause the ethernet driver to call
netdev_tx_reset_queue, which in turn invokes dql_reset.

In this case, dql->limit is reset to 0 while dql->limit_min remains
non-zero value, which is unexpected. The limit should always be
greater than or equal to limit_min.

Signed-off-by: Jing Su <jingsusu@...iglobal.com>
---
 lib/dynamic_queue_limits.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index c1b7638a594a..f97a752e900a 100644
--- a/lib/dynamic_queue_limits.c
+++ b/lib/dynamic_queue_limits.c
@@ -190,7 +190,7 @@ EXPORT_SYMBOL(dql_completed);
 void dql_reset(struct dql *dql)
 {
 	/* Reset all dynamic values */
-	dql->limit = 0;
+	dql->limit = dql->min_limit;
 	dql->num_queued = 0;
 	dql->num_completed = 0;
 	dql->last_obj_cnt = 0;
-- 
2.34.1