netdev - [PATCH AUTOSEL 5.15 055/109] mlxsw: spectrum_dcb: Do not warn about priority changes

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Message-Id: <20220530133825.1933431-55-sashal@kernel.org>
Date:   Mon, 30 May 2022 09:37:31 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Petr Machata <petrm@...dia.com>,
        Maksym Yaremchuk <maksymy@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 055/109] mlxsw: spectrum_dcb: Do not warn about priority changes

From: Petr Machata <petrm@...dia.com>

[ Upstream commit b6b584562cbe7dc357083459d6dd5b171e12cadb ]

The idea behind the warnings is that the user would get warned in case when
more than one priority is configured for a given DSCP value on a netdevice.

The warning is currently wrong, because dcb_ieee_getapp_mask() returns
the first matching entry, not all of them, and the warning will then claim
that some priority is "current", when in fact it is not.

But more importantly, the warning is misleading in general. Consider the
following commands:

 # dcb app flush dev swp19 dscp-prio
 # dcb app add dev swp19 dscp-prio 24:3
 # dcb app replace dev swp19 dscp-prio 24:2

The last command will issue the following warning:

 mlxsw_spectrum3 0000:07:00.0 swp19: Ignoring new priority 2 for DSCP 24 in favor of current value of 3

The reason is that the "replace" command works by first adding the new
value, and then removing all old values. This is the only way to make the
replacement without causing the traffic to be prioritized to whatever the
chip defaults to. The warning is issued in response to adding the new
priority, and then no warning is shown when the old priority is removed.
The upshot is that the canonical way to change traffic prioritization
always produces a warning about ignoring the new priority, but what gets
configured is in fact what the user intended.

An option to just emit warning every time that the prioritization changes
just to make it clear that it happened is obviously unsatisfactory.

Therefore, in this patch, remove the warnings.

Reported-by: Maksym Yaremchuk <maksymy@...dia.com>
Signed-off-by: Petr Machata <petrm@...dia.com>
Signed-off-by: Ido Schimmel <idosch@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c
index 5f92b1691360..aff6d4f35cd2 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c
@@ -168,8 +168,6 @@ static int mlxsw_sp_dcbnl_ieee_setets(struct net_device *dev,
 static int mlxsw_sp_dcbnl_app_validate(struct net_device *dev,
 				       struct dcb_app *app)
 {
-	int prio;
-
 	if (app->priority >= IEEE_8021QAZ_MAX_TCS) {
 		netdev_err(dev, "APP entry with priority value %u is invalid\n",
 			   app->priority);
@@ -183,17 +181,6 @@ static int mlxsw_sp_dcbnl_app_validate(struct net_device *dev,
 				   app->protocol);
 			return -EINVAL;
 		}
-
-		/* Warn about any DSCP APP entries with the same PID. */
-		prio = fls(dcb_ieee_getapp_mask(dev, app));
-		if (prio--) {
-			if (prio < app->priority)
-				netdev_warn(dev, "Choosing priority %d for DSCP %d in favor of previously-active value of %d\n",
-					    app->priority, app->protocol, prio);
-			else if (prio > app->priority)
-				netdev_warn(dev, "Ignoring new priority %d for DSCP %d in favor of current value of %d\n",
-					    app->priority, app->protocol, prio);
-		}
 		break;

 	case IEEE_8021QAZ_APP_SEL_ETHERTYPE:
-- 
2.35.1