netdev - [PATCH v2 net-next 7/7] ipv6: Revert two per-cpu var allocation for RTM

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Message-ID: <20250516022759.44392-8-kuniyu@amazon.com>
Date: Thu, 15 May 2025 19:27:23 -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 v2 net-next 7/7] ipv6: Revert two per-cpu var allocation for RTM_NEWROUTE.

These two commits preallocated two per-cpu variables in
ip6_route_info_create() as fib_nh_common_init() and fib6_nh_init()
were expected to be called under RCU.

  * commit d27b9c40dbd6 ("ipv6: Preallocate nhc_pcpu_rth_output in
    ip6_route_info_create().")
  * commit 5720a328c3e9 ("ipv6: Preallocate rt->fib6_nh->rt6i_pcpu in
    ip6_route_info_create().")

Now these functions can be called without RCU and can use GFP_KERNEL.

Let's revert the commits.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/fib_semantics.c | 10 ++++------
 net/ipv6/route.c         | 34 +++-------------------------------
 2 files changed, 7 insertions(+), 37 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index dabe2b7044ab..d643bd1a0d9d 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -617,12 +617,10 @@ int fib_nh_common_init(struct net *net, struct fib_nh_common *nhc,
 {
 	int err;
 
-	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;
-	}
+	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 dda913ebd2d3..0143262094b0 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3674,12 +3674,10 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
 		goto out;
 
 pcpu_alloc:
+	fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);
 	if (!fib6_nh->rt6i_pcpu) {
-		fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);
-		if (!fib6_nh->rt6i_pcpu) {
-			err = -ENOMEM;
-			goto out;
-		}
+		err = -ENOMEM;
+		goto out;
 	}
 
 	fib6_nh->fib_nh_dev = dev;
@@ -3739,24 +3737,6 @@ 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;
-}
-
 static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 					       gfp_t gfp_flags,
 					       struct netlink_ext_ack *extack)
@@ -3794,12 +3774,6 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 		goto free;
 	}
 
-	if (!cfg->fc_nh_id) {
-		err = fib6_nh_prealloc_percpu(&rt->fib6_nh[0], gfp_flags);
-		if (err)
-			goto free_metrics;
-	}
-
 	if (cfg->fc_flags & RTF_ADDRCONF)
 		rt->dst_nocount = true;
 
@@ -3824,8 +3798,6 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 	rt->fib6_src.plen = cfg->fc_src_len;
 #endif
 	return rt;
-free_metrics:
-	ip_fib_metrics_put(rt->fib6_metrics);
 free:
 	kfree(rt);
 err:
-- 
2.49.0