netdev - [PATCH v1 net-next 08/13] ipv6: Preallocate nhc_pcpu_rth_output in ip6_route_info

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Message-ID: <20250321040131.21057-9-kuniyu@amazon.com>
Date: Thu, 20 Mar 2025 21:00:45 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "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>
CC: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>,
	Kuniyuki Iwashima <kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v1 net-next 08/13] ipv6: Preallocate nhc_pcpu_rth_output in ip6_route_info_create().

ip6_route_info_create_nh() will be called under RCU.

It calls fib_nh_common_init() and allocates nhc->nhc_pcpu_rth_output.

As with the reason for rt->fib6_nh->rt6i_pcpu, we want to avoid
GFP_ATOMIC allocation for nhc->nhc_pcpu_rth_output under RCU.

Let's preallocate it in ip6_route_info_create().

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/fib_semantics.c | 10 ++++++----
 net/ipv6/route.c         |  9 +++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index f68bb9e34c34..5326f1501af0 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -617,10 +617,12 @@ int fib_nh_common_init(struct net *net, struct fib_nh_common *nhc,
 {
 	int err;
 
-	nhc->nhc_pcpu_rth_output = alloc_percpu_gfp(struct rtable __rcu *,
-						    gfp_flags);
-	if (!nhc->nhc_pcpu_rth_output)
-		return -ENOMEM;
+	if (!nhc->nhc_pcpu_rth_output) {
+		nhc->nhc_pcpu_rth_output = alloc_percpu_gfp(struct rtable __rcu *,
+							    gfp_flags);
+		if (!nhc->nhc_pcpu_rth_output)
+			return -ENOMEM;
+	}
 
 	if (encap) {
 		struct lwtunnel_state *lwtstate;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index d50377131506..e65e2c8b7125 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3697,10 +3697,19 @@ void fib6_nh_release_dsts(struct fib6_nh *fib6_nh)
 
 static int fib6_nh_prealloc_percpu(struct fib6_nh *fib6_nh, gfp_t gfp_flags)
 {
+	struct fib_nh_common *nhc = &fib6_nh->nh_common;
+
 	fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);
 	if (!fib6_nh->rt6i_pcpu)
 		return -ENOMEM;
 
+	nhc->nhc_pcpu_rth_output = alloc_percpu_gfp(struct rtable __rcu *,
+						    gfp_flags);
+	if (!nhc->nhc_pcpu_rth_output) {
+		free_percpu(fib6_nh->rt6i_pcpu);
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
-- 
2.48.1