[PATCH 07/14] net: bridge: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Julia Lawall
2024-06-09T08:28:07Z

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/bridge/br_fdb.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index c77591e63841..6d04b48f7e2c 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -73,13 +73,6 @@ static inline int has_expired(const struct net_bridge *br,
time_before_eq(fdb->updated + hold_time(br), jiffies);
}

-static void fdb_rcu_free(struct rcu_head *head)
-{
- struct net_bridge_fdb_entry *ent
- = container_of(head, struct net_bridge_fdb_entry, rcu);
- kmem_cache_free(br_fdb_cache, ent);
-}
-
static int fdb_to_nud(const struct net_bridge *br,
const struct net_bridge_fdb_entry *fdb)
{
@@ -329,7 +322,7 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f,
if (test_and_clear_bit(BR_FDB_DYNAMIC_LEARNED, &f->flags))
atomic_dec(&br->fdb_n_learned);
fdb_notify(br, f, RTM_DELNEIGH, swdev_notify);
- call_rcu(&f->rcu, fdb_rcu_free);
+ kfree_rcu(f, rcu);
}

/* Delete a local entry if no other port had the same address.