[PATCH 04/14] xfrm6_tunnel: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Julia Lawall
2024-06-09T08:28:04Z

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/ipv6/xfrm6_tunnel.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index bf140ef781c1..c3c893ddb6ee 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -178,12 +178,6 @@ __be32 xfrm6_tunnel_alloc_spi(struct net *net, xfrm_address_t *saddr)
}
EXPORT_SYMBOL(xfrm6_tunnel_alloc_spi);

-static void x6spi_destroy_rcu(struct rcu_head *head)
-{
- kmem_cache_free(xfrm6_tunnel_spi_kmem,
- container_of(head, struct xfrm6_tunnel_spi, rcu_head));
-}
-
static void xfrm6_tunnel_free_spi(struct net *net, xfrm_address_t *saddr)
{
struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
@@ -200,7 +194,7 @@ static void xfrm6_tunnel_free_spi(struct net *net, xfrm_address_t *saddr)
if (refcount_dec_and_test(&x6spi->refcnt)) {
hlist_del_rcu(&x6spi->list_byaddr);
hlist_del_rcu(&x6spi->list_byspi);
- call_rcu(&x6spi->rcu_head, x6spi_destroy_rcu);
+ kfree_rcu(x6spi, rcu_head);
break;
}
}