inetpeer: update inetpeer timestamp in inet_getpeer()

BugLink: https://bugs.launchpad.net/bugs/2111953

[ Upstream commit 50b362f ]

inet_putpeer() will be removed in the following patch,
because we will no longer use refcounts.

Update inetpeer timestamp (p->dtime) at lookup time.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241215175629.1248773-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: a853c60 ("inetpeer: do not get a refcount in inet_getpeer()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

Author: edumazet

net/ipv4/inetpeer.c

@@ -98,6 +98,7 @@ static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
 {
 	struct rb_node **pp, *parent, *next;
 	struct inet_peer *p;
+	u32 now;
 
 	pp = &base->rb_root.rb_node;
 	parent = NULL;
@@ -113,6 +114,9 @@ static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
 		if (cmp == 0) {
 			if (!refcount_inc_not_zero(&p->refcnt))
 				break;
+			now = jiffies;
+			if (READ_ONCE(p->dtime) != now)
+				WRITE_ONCE(p->dtime, now);
 			return p;
 		}
 		if (gc_stack) {
@@ -158,9 +162,6 @@ static void inet_peer_gc(struct inet_peer_base *base,
 	for (i = 0; i < gc_cnt; i++) {
 		p = gc_stack[i];
 
-		/* The READ_ONCE() pairs with the WRITE_ONCE()
-		 * in inet_putpeer()
-		 */
 		delta = (__u32)jiffies - READ_ONCE(p->dtime);
 
 		if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
@@ -232,11 +233,6 @@ EXPORT_SYMBOL_GPL(inet_getpeer);
 
 void inet_putpeer(struct inet_peer *p)
 {
-	/* The WRITE_ONCE() pairs with itself (we run lockless)
-	 * and the READ_ONCE() in inet_peer_gc()
-	 */
-	WRITE_ONCE(p->dtime, (__u32)jiffies);
-
 	if (refcount_dec_and_test(&p->refcnt))
 		call_rcu(&p->rcu, inetpeer_free_rcu);
 }