netdev - [PATCH 04/14] xfrm6_tunnel: replace call_rcu by kfree_rcu for simple kmem_cache

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Message-Id: <20240609082726.32742-5-Julia.Lawall@inria.fr>
Date: Sun,  9 Jun 2024 10:27:16 +0200
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: Steffen Klassert <steffen.klassert@...unet.com>
Cc: kernel-janitors@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 04/14] xfrm6_tunnel: 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/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;
 			}
 		}