netdev - [net-next 5/9] i40e: use WARN_ONCE to replace the commented BUG

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Message-Id: <20180522174527.19680-6-jeffrey.t.kirsher@intel.com>
Date:   Tue, 22 May 2018 10:45:23 -0700
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Jacob Keller <jacob.e.keller@...el.com>, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 5/9] i40e: use WARN_ONCE to replace the commented BUG_ON size check

From: Jacob Keller <jacob.e.keller@...el.com>

We don't really want to use BUG_ON here since that would completely
crash the kernel, thus the reason we commented it out. We *can't* use
BUILD_BUG_ON because at least now (a) the sizes aren't constant (we are
fixing this) and (b) not all compilers are smart enough to understand
that "p - data" is a constant.

Instead, just use a WARN_ONCE so that the first time we end up with an
incorrect size we will dump a stack trace and a message, hopefully
highlighting the issues early in testing.

Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/i40e/i40e_ethtool.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
index c50ed2d391e1..32bcb6a2a590 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
@@ -1792,8 +1792,8 @@ static void i40e_get_stat_strings(struct net_device *netdev, u8 *data)
 	struct i40e_netdev_priv *np = netdev_priv(netdev);
 	struct i40e_vsi *vsi = np->vsi;
 	struct i40e_pf *pf = vsi->back;
-	char *p = (char *)data;
 	unsigned int i;
+	u8 *p = data;
 
 	for (i = 0; i < I40E_NETDEV_STATS_LEN; i++) {
 		snprintf(p, ETH_GSTRING_LEN, "%s",
@@ -1864,7 +1864,9 @@ static void i40e_get_stat_strings(struct net_device *netdev, u8 *data)
 			 "port.rx_priority_%u_xon_2_xoff", i);
 		p += ETH_GSTRING_LEN;
 	}
-	/* BUG_ON(p - data != I40E_STATS_LEN * ETH_GSTRING_LEN); */
+
+	WARN_ONCE(p - data != i40e_get_stats_count(netdev) * ETH_GSTRING_LEN,
+		  "stat strings count mismatch!");
 }
 
 static void i40e_get_priv_flag_strings(struct net_device *netdev, u8 *data)
-- 
2.17.0