linux-kernel - [PATCH 02/14] net: replace call_rcu by kfree_rcu for simple kmem_cache

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Date: Sun,  9 Jun 2024 10:27:14 +0200
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: "David S. Miller" <davem@...emloft.net>
Cc: kernel-janitors@...r.kernel.org,
	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 02/14] net: 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/ipv4/fib_trie.c |    8 +-------
 net/ipv4/inetpeer.c |    9 ++-------
 net/ipv6/ip6_fib.c  |    9 +--------
 3 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index f474106464d2..3ed92e583417 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -292,15 +292,9 @@ static const int inflate_threshold = 50;
 static const int halve_threshold_root = 15;
 static const int inflate_threshold_root = 30;
 
-static void __alias_free_mem(struct rcu_head *head)
-{
-	struct fib_alias *fa = container_of(head, struct fib_alias, rcu);
-	kmem_cache_free(fn_alias_kmem, fa);
-}
-
 static inline void alias_free_mem_rcu(struct fib_alias *fa)
 {
-	call_rcu(&fa->rcu, __alias_free_mem);
+	kfree_rcu(fa, rcu);
 }
 
 #define TNODE_VMALLOC_MAX \
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 5bd759963451..5ab56f4cb529 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -128,11 +128,6 @@ static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
 	return NULL;
 }
 
-static void inetpeer_free_rcu(struct rcu_head *head)
-{
-	kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
-}
-
 /* perform garbage collect on all items stacked during a lookup */
 static void inet_peer_gc(struct inet_peer_base *base,
 			 struct inet_peer *gc_stack[],
@@ -168,7 +163,7 @@ static void inet_peer_gc(struct inet_peer_base *base,
 		if (p) {
 			rb_erase(&p->rb_node, &base->rb_root);
 			base->total--;
-			call_rcu(&p->rcu, inetpeer_free_rcu);
+			kfree_rcu(p, rcu);
 		}
 	}
 }
@@ -242,7 +237,7 @@ void inet_putpeer(struct inet_peer *p)
 	WRITE_ONCE(p->dtime, (__u32)jiffies);
 
 	if (refcount_dec_and_test(&p->refcnt))
-		call_rcu(&p->rcu, inetpeer_free_rcu);
+		kfree_rcu(p, rcu);
 }
 EXPORT_SYMBOL_GPL(inet_putpeer);
 
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index d9c9a542a414..bf6908010641 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -198,16 +198,9 @@ static void node_free_immediate(struct net *net, struct fib6_node *fn)
 	net->ipv6.rt6_stats->fib_nodes--;
 }
 
-static void node_free_rcu(struct rcu_head *head)
-{
-	struct fib6_node *fn = container_of(head, struct fib6_node, rcu);
-
-	kmem_cache_free(fib6_node_kmem, fn);
-}
-
 static void node_free(struct net *net, struct fib6_node *fn)
 {
-	call_rcu(&fn->rcu, node_free_rcu);
+	kfree_rcu(fn, rcu);
 	net->ipv6.rt6_stats->fib_nodes--;
 }