[PATCH 14/14] netfilter: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Julia Lawall
2024-06-09T08:28:12Z

Since SLOB was removed, it is not necessary to use call_rcu
when the callback only performs kmem_cache_free. Use
kfree_rcu() directly.

The changes were done using the following Coccinelle semantic patch.
This semantic patch is designed to ignore cases where the callback
function is used in another way.

// <smpl>
@r@
expression e;
local idexpression e2;
identifier cb,f;
position p;
@@

(
call_rcu(...,e2)
|
call_rcu(&e->f,cb@p)
)

@r1@
type T;
identifier x,r.cb;
@@

cb(...) {
(
kmem_cache_free(...);
|
T x = ...;
kmem_cache_free(...,x);
|
T x;
x = ...;
kmem_cache_free(...,x);
)
}

@s depends on r1@
position p != r.p;
identifier r.cb;
@@

cb@p

@script:ocaml@
cb << r.cb;
p << s.p;
@@

Printf.eprintf "Other use of %s at %s:%d\n"
cb (List.hd p).file (List.hd p).line

@depends on r1 && !s@
expression e;
identifier r.cb,f;
position r.p;
@@

- call_rcu(&e->f,cb@p)
+ kfree_rcu(e,f)

@r1a depends on !s@
type T;
identifier x,r.cb;
@@

- cb(...) {
(
- kmem_cache_free(...);
|
- T x = ...;
- kmem_cache_free(...,x);
|
- T x;
- x = ...;
- kmem_cache_free(...,x);
)
- }
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

---
net/netfilter/nf_conncount.c | 10 +---------
net/netfilter/nf_conntrack_expect.c | 10 +---------
net/netfilter/xt_hashlimit.c | 9 +--------
3 files changed, 3 insertions(+), 26 deletions(-)

diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c
index 8715617b02fe..587bfcb79723 100644
--- a/net/netfilter/nf_conncount.c
+++ b/net/netfilter/nf_conncount.c
@@ -275,14 +275,6 @@ bool nf_conncount_gc_list(struct net *net,
}
EXPORT_SYMBOL_GPL(nf_conncount_gc_list);

-static void __tree_nodes_free(struct rcu_head *h)
-{
- struct nf_conncount_rb *rbconn;
-
- rbconn = container_of(h, struct nf_conncount_rb, rcu_head);
- kmem_cache_free(conncount_rb_cachep, rbconn);
-}
-
/* caller must hold tree nf_conncount_locks[] lock */
static void tree_nodes_free(struct rb_root *root,
struct nf_conncount_rb *gc_nodes[],
@@ -295,7 +287,7 @@ static void tree_nodes_free(struct rb_root *root,
spin_lock(&rbconn->list.list_lock);
if (!rbconn->list.count) {
rb_erase(&rbconn->node, root);
- call_rcu(&rbconn->rcu_head, __tree_nodes_free);
+ kfree_rcu(rbconn, rcu_head);
}
spin_unlock(&rbconn->list.list_lock);
}
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index 21fa550966f0..9dcaef6f3663 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -367,18 +367,10 @@ void nf_ct_expect_init(struct nf_conntrack_expect *exp, unsigned int class,
}
EXPORT_SYMBOL_GPL(nf_ct_expect_init);

-static void nf_ct_expect_free_rcu(struct rcu_head *head)
-{
- struct nf_conntrack_expect *exp;
-
- exp = container_of(head, struct nf_conntrack_expect, rcu);
- kmem_cache_free(nf_ct_expect_cachep, exp);
-}
-
void nf_ct_expect_put(struct nf_conntrack_expect *exp)
{
if (refcount_dec_and_test(&exp->use))
- call_rcu(&exp->rcu, nf_ct_expect_free_rcu);
+ kfree_rcu(exp, rcu);
}
EXPORT_SYMBOL_GPL(nf_ct_expect_put);

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 0859b8f76764..c2b9b954eb53 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -256,18 +256,11 @@ dsthash_alloc_init(struct xt_hashlimit_htable *ht,
return ent;
}

-static void dsthash_free_rcu(struct rcu_head *head)
-{
- struct dsthash_ent *ent = container_of(head, struct dsthash_ent, rcu);
-
- kmem_cache_free(hashlimit_cachep, ent);
-}
-
static inline void
dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
{
hlist_del_rcu(&ent->node);
- call_rcu(&ent->rcu, dsthash_free_rcu);
+ kfree_rcu(ent, rcu);
ht->count--;
}
static void htable_gc(struct work_struct *work);