[PATCH 13/14] kcm: 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/kcm/kcmsock.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 2f191e50d4fc..fbb730cd2d38 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1580,14 +1580,6 @@ static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
return err;
}

-static void free_mux(struct rcu_head *rcu)
-{
- struct kcm_mux *mux = container_of(rcu,
- struct kcm_mux, rcu);
-
- kmem_cache_free(kcm_muxp, mux);
-}
-
static void release_mux(struct kcm_mux *mux)
{
struct kcm_net *knet = mux->knet;
@@ -1615,7 +1607,7 @@ static void release_mux(struct kcm_mux *mux)
knet->count--;
mutex_unlock(&knet->mutex);

- call_rcu(&mux->rcu, free_mux);
+ kfree_rcu(mux, rcu);
}

static void kcm_done(struct kcm_sock *kcm)