netdev - [PATCH net] bonding: add ACCESS_ONCE() and change local var names

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Date:	Thu,  5 Dec 2013 15:10:44 +0100
From:	Nikolay Aleksandrov <nikolay@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Nikolay Aleksandrov <nikolay@...hat.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Jay Vosburgh <fubar@...ibm.com>,
	Veaceslav Falico <vfalico@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net] bonding: add ACCESS_ONCE() and change local var names

We use bond->params.packets_per_slave without any locking in 2 places:
bond_rr_gen_id() and bonding_show_packets_per_slave(), so as a
precaution and to show what's intended, add ACCESS_ONCE() when fetching
it in the local variable.
Also rename the local variables to pps_tmp so they're not with the name
of the module parameter to avoid confusion.

CC: Andy Gospodarek <andy@...yhouse.net>
CC: Jay Vosburgh <fubar@...ibm.com>
CC: Veaceslav Falico <vfalico@...hat.com>
CC: David S. Miller <davem@...emloft.net>
CC: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>
---
Please note that this patch is on top of the one I posted earlier today
("bonding: fix packets_per_slave showing").
Also I'm not adding ACCESS_ONCE() to bond_check_params() now as we don't
export almost anything through /sys/module/bonding/parameters and moreover
it's a new feature and thus net-next material if such an export is to be
made.

 drivers/net/bonding/bond_main.c  | 7 +++----
 drivers/net/bonding/bond_sysfs.c | 8 ++++----
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 36eab0c..3ec3036 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3590,10 +3590,10 @@ void bond_xmit_slave_id(struct bonding *bond, struct sk_buff *skb, int slave_id)
  */
 static u32 bond_rr_gen_slave_id(struct bonding *bond)
 {
-	int packets_per_slave = bond->params.packets_per_slave;
+	int pps_tmp = ACCESS_ONCE(bond->params.packets_per_slave);
 	u32 slave_id;
 
-	switch (packets_per_slave) {
+	switch (pps_tmp) {
 	case 0:
 		slave_id = prandom_u32();
 		break;
@@ -3601,8 +3601,7 @@ static u32 bond_rr_gen_slave_id(struct bonding *bond)
 		slave_id = bond->rr_tx_counter;
 		break;
 	default:
-		slave_id = reciprocal_divide(bond->rr_tx_counter,
-					     packets_per_slave);
+		slave_id = reciprocal_divide(bond->rr_tx_counter, pps_tmp);
 		break;
 	}
 	bond->rr_tx_counter++;
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 0ae580b..1a0ae85 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -1635,12 +1635,12 @@ static ssize_t bonding_show_packets_per_slave(struct device *d,
 					      char *buf)
 {
 	struct bonding *bond = to_bond(d);
-	unsigned int packets_per_slave = bond->params.packets_per_slave;
+	unsigned int pps_tmp = ACCESS_ONCE(bond->params.packets_per_slave);
 
-	if (packets_per_slave > 1)
-		packets_per_slave = reciprocal_value(packets_per_slave);
+	if (pps_tmp > 1)
+		pps_tmp = reciprocal_value(pps_tmp);
 
-	return sprintf(buf, "%u\n", packets_per_slave);
+	return sprintf(buf, "%u\n", pps_tmp);
 }
 
 static ssize_t bonding_store_packets_per_slave(struct device *d,
-- 
1.8.1.4

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