[PATCH 02/14] net: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Julia Lawall
2024-06-09T08:28:02Z

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/ipv4/fib_trie.c | 8 +-------
net/ipv4/inetpeer.c | 9 ++-------
net/ipv6/ip6_fib.c | 9 +--------
3 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index f474106464d2..3ed92e583417 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -292,15 +292,9 @@ static const int inflate_threshold = 50;
static const int halve_threshold_root = 15;
static const int inflate_threshold_root = 30;

-static void __alias_free_mem(struct rcu_head *head)
-{
- struct fib_alias *fa = container_of(head, struct fib_alias, rcu);
- kmem_cache_free(fn_alias_kmem, fa);
-}
-
static inline void alias_free_mem_rcu(struct fib_alias *fa)
{
- call_rcu(&fa->rcu, __alias_free_mem);
+ kfree_rcu(fa, rcu);
}

#define TNODE_VMALLOC_MAX \
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 5bd759963451..5ab56f4cb529 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -128,11 +128,6 @@ static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
return NULL;
}

-static void inetpeer_free_rcu(struct rcu_head *head)
-{
- kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
-}
-
/* perform garbage collect on all items stacked during a lookup */
static void inet_peer_gc(struct inet_peer_base *base,
struct inet_peer *gc_stack[],
@@ -168,7 +163,7 @@ static void inet_peer_gc(struct inet_peer_base *base,
if (p) {
rb_erase(&p->rb_node, &base->rb_root);
base->total--;
- call_rcu(&p->rcu, inetpeer_free_rcu);
+ kfree_rcu(p, rcu);
}
}
}
@@ -242,7 +237,7 @@ void inet_putpeer(struct inet_peer *p)
WRITE_ONCE(p->dtime, (__u32)jiffies);

if (refcount_dec_and_test(&p->refcnt))
- call_rcu(&p->rcu, inetpeer_free_rcu);
+ kfree_rcu(p, rcu);
}
EXPORT_SYMBOL_GPL(inet_putpeer);

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index d9c9a542a414..bf6908010641 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -198,16 +198,9 @@ static void node_free_immediate(struct net *net, struct fib6_node *fn)
net->ipv6.rt6_stats->fib_nodes--;
}

-static void node_free_rcu(struct rcu_head *head)
-{
- struct fib6_node *fn = container_of(head, struct fib6_node, rcu);
-
- kmem_cache_free(fib6_node_kmem, fn);
-}
-
static void node_free(struct net *net, struct fib6_node *fn)
{
- call_rcu(&fn->rcu, node_free_rcu);
+ kfree_rcu(fn, rcu);
net->ipv6.rt6_stats->fib_nodes--;
}