[B.A.T.M.A.N.] [PATCH] batman-adv: don't use call_rcu if not needed

[B.A.T.M.A.N.] [PATCH] batman-adv: don't use call_rcu if not needed

[Antonio Quartulli]

batadv_tt_global_entry_free_ref uses call_rcu to schedule a
function which will only free the global entry itself.

For this reason call_rcu is useless and kfree_rcu can be
used to simplify the code.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
 compat.c            | 11 +++++++++++
 translation-table.c | 20 ++++++--------------
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/compat.c b/compat.c
index 1f3a39d..6226f81 100644
--- a/compat.c
+++ b/compat.c
@@ -27,6 +27,17 @@
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 0, 0)
 
+void batadv_free_rcu_tt_global_entry(struct rcu_head *rcu)
+{
+	struct batadv_tt_common_entry *common;
+	struct batadv_tt_global_entry *global;
+
+	common = container_of(rcu, struct batadv_tt_common_entry, rcu);
+	global = container_of(common, struct batadv_tt_common_entry, common);
+
+	kfree(global);
+}
+
 void batadv_free_rcu_gw_node(struct rcu_head *rcu)
 {
 	struct batadv_gw_node *gw_node;
diff --git a/translation-table.c b/translation-table.c
index df6b5cd..44e7789 100644
--- a/translation-table.c
+++ b/translation-table.c
@@ -117,25 +117,17 @@ batadv_tt_local_entry_free_ref(struct batadv_tt_local_entry *tt_local_entry)
 		kfree_rcu(tt_local_entry, common.rcu);
 }
 
-static void batadv_tt_global_entry_free_rcu(struct rcu_head *rcu)
-{
-	struct batadv_tt_common_entry *tt_common_entry;
-	struct batadv_tt_global_entry *tt_global_entry;
-
-	tt_common_entry = container_of(rcu, struct batadv_tt_common_entry, rcu);
-	tt_global_entry = container_of(tt_common_entry,
-				       struct batadv_tt_global_entry, common);
-
-	kfree(tt_global_entry);
-}
-
+/**
+ * batadv_tt_global_entry_free_ref - decrement the refcounter for a
+ *  tt_global_entry and possibly free it
+ * @tt_global_entry: the object to free
+ */
 static void
 batadv_tt_global_entry_free_ref(struct batadv_tt_global_entry *tt_global_entry)
 {
 	if (atomic_dec_and_test(&tt_global_entry->common.refcount)) {
 		batadv_tt_global_del_orig_list(tt_global_entry);
-		call_rcu(&tt_global_entry->common.rcu,
-			 batadv_tt_global_entry_free_rcu);
+		kfree_rcu(tt_global_entry, common.rcu);
 	}
 }
 
-- 
1.8.1.5

Re: [B.A.T.M.A.N.] [PATCH] batman-adv: don't use call_rcu if not needed

[Antonio Quartulli]

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On Mon, May 06, 2013 at 09:39:52PM +0200, Antonio Quartulli wrote:
> batadv_tt_global_entry_free_ref uses call_rcu to schedule a
> function which will only free the global entry itself.
> 
> For this reason call_rcu is useless and kfree_rcu can be
> used to simplify the code.
> 
> Signed-off-by: Antonio Quartulli <ordex@autistici.org>
> ---
>  compat.c            | 11 +++++++++++
>  translation-table.c | 20 ++++++--------------
>  2 files changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/compat.c b/compat.c
> index 1f3a39d..6226f81 100644
> --- a/compat.c
> +++ b/compat.c
> @@ -27,6 +27,17 @@
>  
>  #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 0, 0)

This compat code has not been tested because of lack of kernels...

Cheers,

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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Re: [B.A.T.M.A.N.] [PATCH] batman-adv: don't use call_rcu if not needed

[Marek Lindner]

On Tuesday, May 07, 2013 03:39:52 Antonio Quartulli wrote:
> +/**
> + * batadv_tt_global_entry_free_ref - decrement the refcounter for a
> + *  tt_global_entry and possibly free it
> + * @tt_global_entry: the object to free
> + */
>  static void
>  batadv_tt_global_entry_free_ref(struct batadv_tt_global_entry
> *tt_global_entry) {
>         if (atomic_dec_and_test(&tt_global_entry->common.refcount)) {
>                 batadv_tt_global_del_orig_list(tt_global_entry);
> -               call_rcu(&tt_global_entry->common.rcu,
> -                        batadv_tt_global_entry_free_rcu);
> +               kfree_rcu(tt_global_entry, common.rcu);
>         }
>  }

You are replacing 2 container_of() calls with a single one. If you are sure 
that works why doesn't the compat code do that same ?

Cheers,
Marek