Commit-ID:  4be2b04e43fd3d8164d7aeb1808e47fbeb0c0de0
Gitweb:     https://git.kernel.org/tip/4be2b04e43fd3d8164d7aeb1808e47fbeb0c0de0
Author:     Paul E. McKenney <[email protected]>
AuthorDate: Mon, 9 Oct 2017 12:09:04 -0700
Committer:  Paul E. McKenney <[email protected]>
CommitDate: Mon, 4 Dec 2017 10:52:57 -0800

netfilter: Remove now-redundant smp_read_barrier_depends()

READ_ONCE() now implies smp_read_barrier_depends(), which means that
the instances in arpt_do_table(), ipt_do_table(), and ip6t_do_table()
are now redundant.  This commit removes them and adjusts the comments.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Pablo Neira Ayuso <[email protected]>
Cc: Jozsef Kadlecsik <[email protected]>
Cc: Florian Westphal <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
---
 net/ipv4/netfilter/arp_tables.c | 7 +------
 net/ipv4/netfilter/ip_tables.c  | 7 +------
 net/ipv6/netfilter/ip6_tables.c | 7 +------
 3 files changed, 3 insertions(+), 18 deletions(-)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index f88221a..d242c2d 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -202,13 +202,8 @@ unsigned int arpt_do_table(struct sk_buff *skb,
 
        local_bh_disable();
        addend = xt_write_recseq_begin();
-       private = table->private;
+       private = READ_ONCE(table->private); /* Address dependency. */
        cpu     = smp_processor_id();
-       /*
-        * Ensure we load private-> members after we've fetched the base
-        * pointer.
-        */
-       smp_read_barrier_depends();
        table_base = private->entries;
        jumpstack  = (struct arpt_entry **)private->jumpstack[cpu];
 
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 4cbe5e8..46866cc 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -260,13 +260,8 @@ ipt_do_table(struct sk_buff *skb,
        WARN_ON(!(table->valid_hooks & (1 << hook)));
        local_bh_disable();
        addend = xt_write_recseq_begin();
-       private = table->private;
+       private = READ_ONCE(table->private); /* Address dependency. */
        cpu        = smp_processor_id();
-       /*
-        * Ensure we load private-> members after we've fetched the base
-        * pointer.
-        */
-       smp_read_barrier_depends();
        table_base = private->entries;
        jumpstack  = (struct ipt_entry **)private->jumpstack[cpu];
 
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index f06e250..ac1db84 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -282,12 +282,7 @@ ip6t_do_table(struct sk_buff *skb,
 
        local_bh_disable();
        addend = xt_write_recseq_begin();
-       private = table->private;
-       /*
-        * Ensure we load private-> members after we've fetched the base
-        * pointer.
-        */
-       smp_read_barrier_depends();
+       private = READ_ONCE(table->private); /* Address dependency. */
        cpu        = smp_processor_id();
        table_base = private->entries;
        jumpstack  = (struct ip6t_entry **)private->jumpstack[cpu];

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