linux-kernel - [PATCH 10/14] can: gw: replace call_rcu by kfree_rcu for simple kmem_cache

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Date: Sun,  9 Jun 2024 10:27:22 +0200
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: Oliver Hartkopp <socketcan@...tkopp.net>
Cc: kernel-janitors@...r.kernel.org,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	linux-can@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 10/14] can: gw: 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/can/gw.c |   13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/net/can/gw.c b/net/can/gw.c
index 37528826935e..ffb9870e2d01 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -577,13 +577,6 @@ static inline void cgw_unregister_filter(struct net *net, struct cgw_job *gwj)
 			  gwj->ccgw.filter.can_mask, can_can_gw_rcv, gwj);
 }
 
-static void cgw_job_free_rcu(struct rcu_head *rcu_head)
-{
-	struct cgw_job *gwj = container_of(rcu_head, struct cgw_job, rcu);
-
-	kmem_cache_free(cgw_cache, gwj);
-}
-
 static int cgw_notifier(struct notifier_block *nb,
 			unsigned long msg, void *ptr)
 {
@@ -603,7 +596,7 @@ static int cgw_notifier(struct notifier_block *nb,
 			if (gwj->src.dev == dev || gwj->dst.dev == dev) {
 				hlist_del(&gwj->list);
 				cgw_unregister_filter(net, gwj);
-				call_rcu(&gwj->rcu, cgw_job_free_rcu);
+				kfree_rcu(gwj, rcu);
 			}
 		}
 	}
@@ -1168,7 +1161,7 @@ static void cgw_remove_all_jobs(struct net *net)
 	hlist_for_each_entry_safe(gwj, nx, &net->can.cgw_list, list) {
 		hlist_del(&gwj->list);
 		cgw_unregister_filter(net, gwj);
-		call_rcu(&gwj->rcu, cgw_job_free_rcu);
+		kfree_rcu(gwj, rcu);
 	}
 }
 
@@ -1236,7 +1229,7 @@ static int cgw_remove_job(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 		hlist_del(&gwj->list);
 		cgw_unregister_filter(net, gwj);
-		call_rcu(&gwj->rcu, cgw_job_free_rcu);
+		kfree_rcu(gwj, rcu);
 		err = 0;
 		break;
 	}