linux-kernel - [PATCH 07/14] net: bridge: replace call_rcu by kfree_rcu for simple kmem_cache

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Date: Sun,  9 Jun 2024 10:27:19 +0200
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: Roopa Prabhu <roopa@...dia.com>
Cc: kernel-janitors@...r.kernel.org,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	bridge@...ts.linux.dev,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 07/14] net: bridge: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

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@...ia.fr>
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Vlastimil Babka <vbabka@...e.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.