linux-kernel - [PATCH AUTOSEL 6.12 042/486] dql: Fix dql->limit value when reset.

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Message-Id: <20250505223922.2682012-42-sashal@kernel.org>
Date: Mon,  5 May 2025 18:31:58 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Jing Su <jingsusu@...iglobal.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 6.12 042/486] dql: Fix dql->limit value when reset.

From: Jing Su <jingsusu@...iglobal.com>

[ Upstream commit 3a17f23f7c36bac3a3584aaf97d3e3e0b2790396 ]

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>
Link: https://patch.msgid.link/Z9qHD1s/NEuQBdgH@pilot-ThinkCentre-M930t-N000
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 e49deddd3de9f..7d1dfbb99b397 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;
-- 
2.39.5