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@didiglobal.com>
Link: https://patch.msgid.link/Z9qHD1s/NEuQBdgH@pilot-ThinkCentre-M930t-N000
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index c1b7638a594ac43f947e00decabbd3468dcb53de..f97a752e900a0d6afa711b2f438f1e9f2dba4b5b 100644 (file)
--- 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;