net: restore gnet_stats_basic to previous definition

In 5e140dfc1fe87eae27846f193086724806b33c7d "net: reorder struct Qdisc
for better SMP performance" the definition of struct gnet_stats_basic
changed incompatibly, as copies of this struct are shipped to
userland via netlink.

Restoring old behavior is not welcome, for performance reason.

Fix is to use a private structure for kernel, and
teach gnet_stats_copy_basic() to convert from kernel to user land,
using legacy structure (struct gnet_stats_basic)

Based on a report and initial patch from Michael Spang.

Reported-by: Michael Spang <mspang@csclub.uwaterloo.ca>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 14 insertions, 9 deletions

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index 78e5bfc454ae..493775f4f2f1 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -81,7 +81,7 @@
 struct gen_estimator
 {
         struct list_head        list;
-        struct gnet_stats_basic *bstats;
+        struct gnet_stats_basic_packed  *bstats;
         struct gnet_stats_rate_est      *rate_est;
         spinlock_t              *stats_lock;
         int                     ewma_log;
@@ -165,7 +165,7 @@ static void gen_add_node(struct gen_estimator *est)
 }
 
 static
-struct gen_estimator *gen_find_node(const struct gnet_stats_basic *bstats,
+struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
                                     const struct gnet_stats_rate_est *rate_est)
 {
         struct rb_node *p = est_root.rb_node;
@@ -202,7 +202,7 @@ struct gen_estimator *gen_find_node(const struct gnet_stats_basic *bstats,
  *
  * NOTE: Called under rtnl_mutex
  */
-int gen_new_estimator(struct gnet_stats_basic *bstats,
+int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
                       struct gnet_stats_rate_est *rate_est,
                       spinlock_t *stats_lock,
                       struct nlattr *opt)
@@ -262,7 +262,7 @@ static void __gen_kill_estimator(struct rcu_head *head)
  *
  * NOTE: Called under rtnl_mutex
  */
-void gen_kill_estimator(struct gnet_stats_basic *bstats,
+void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
                         struct gnet_stats_rate_est *rate_est)
 {
         struct gen_estimator *e;
@@ -292,7 +292,7 @@ EXPORT_SYMBOL(gen_kill_estimator);
  *
  * Returns 0 on success or a negative error code.
  */
-int gen_replace_estimator(struct gnet_stats_basic *bstats,
+int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
                           struct gnet_stats_rate_est *rate_est,
                           spinlock_t *stats_lock, struct nlattr *opt)
 {
@@ -308,7 +308,7 @@ EXPORT_SYMBOL(gen_replace_estimator);
  *
  * Returns true if estimator is active, and false if not.
  */
-bool gen_estimator_active(const struct gnet_stats_basic *bstats,
+bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
                           const struct gnet_stats_rate_est *rate_est)
 {
         ASSERT_RTNL();
diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index c3d0ffeac243..8569310268ab 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -106,16 +106,21 @@ gnet_stats_start_copy(struct sk_buff *skb, int type, spinlock_t *lock,
  * if the room in the socket buffer was not sufficient.
  */
 int
-gnet_stats_copy_basic(struct gnet_dump *d, struct gnet_stats_basic *b)
+gnet_stats_copy_basic(struct gnet_dump *d, struct gnet_stats_basic_packed *b)
 {
         if (d->compat_tc_stats) {
                 d->tc_stats.bytes = b->bytes;
                 d->tc_stats.packets = b->packets;
         }
 
-        if (d->tail)
-                return gnet_stats_copy(d, TCA_STATS_BASIC, b, sizeof(*b));
+        if (d->tail) {
+                struct gnet_stats_basic sb;
 
+                memset(&sb, 0, sizeof(sb));
+                sb.bytes = b->bytes;
+                sb.packets = b->packets;
+                return gnet_stats_copy(d, TCA_STATS_BASIC, &sb, sizeof(sb));
+        }
         return 0;
 }