ipvs: Use flexible array for MH lookup table

[PATCH] ipvs: Use flexible array for MH lookup table

Posted by Rosen Penev 6 days, 1 hour ago

Store the Maglev hash lookup table in the scheduler state
allocation instead of allocating it separately.

This keeps the lookup table tied to the RCU-freed state lifetime and
simplifies the allocation and cleanup paths.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 net/netfilter/ipvs/ip_vs_mh.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_mh.c b/net/netfilter/ipvs/ip_vs_mh.c
index 020863047562..d31d3c6d4216 100644
--- a/net/netfilter/ipvs/ip_vs_mh.c
+++ b/net/netfilter/ipvs/ip_vs_mh.c
@@ -59,11 +59,11 @@ static int primes[] = {251, 509, 1021, 2039, 4093,
 
 struct ip_vs_mh_state {
 	struct rcu_head			rcu_head;
-	struct ip_vs_mh_lookup		*lookup;
 	struct ip_vs_mh_dest_setup	*dest_setup;
 	hsiphash_key_t			hash1, hash2;
 	int				gcd;
 	int				rshift;
+	struct ip_vs_mh_lookup		lookup[];
 };
 
 static inline void generate_hash_secret(hsiphash_key_t *hash1,
@@ -372,7 +372,6 @@ static void ip_vs_mh_state_free(struct rcu_head *head)
 	struct ip_vs_mh_state *s;
 
 	s = container_of(head, struct ip_vs_mh_state, rcu_head);
-	kfree(s->lookup);
 	kfree(s);
 }
 
@@ -382,16 +381,10 @@ static int ip_vs_mh_init_svc(struct ip_vs_service *svc)
 	struct ip_vs_mh_state *s;
 
 	/* Allocate the MH table for this service */
-	s = kzalloc_obj(*s);
+	s = kzalloc_flex(*s, lookup, IP_VS_MH_TAB_SIZE);
 	if (!s)
 		return -ENOMEM;
 
-	s->lookup = kzalloc_objs(struct ip_vs_mh_lookup, IP_VS_MH_TAB_SIZE);
-	if (!s->lookup) {
-		kfree(s);
-		return -ENOMEM;
-	}
-
 	generate_hash_secret(&s->hash1, &s->hash2);
 	s->gcd = ip_vs_mh_gcd_weight(svc);
 	s->rshift = ip_vs_mh_shift_weight(svc, s->gcd);
-- 
2.54.0

Re: [PATCH] ipvs: Use flexible array for MH lookup table

Posted by Julian Anastasov 2 days, 10 hours ago

	Hello,

On Mon, 18 May 2026, Rosen Penev wrote:

> Store the Maglev hash lookup table in the scheduler state
> allocation instead of allocating it separately.
> 
> This keeps the lookup table tied to the RCU-freed state lifetime and
> simplifies the allocation and cleanup paths.
> 
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

	Thanks for the efforts but it is better to keep the table 
allocated separately. As Sashiko [1] points out, the table size is
properly selected and we risk double-sized allocations if we apply
this patch.

	As for the problem in ip_vs_edit_service(), I have to
provide separate bugfix...

[1]:
https://sashiko.dev/#/patchset/20260519015506.634185-1-rosenp%40gmail.com

Regards

--
Julian Anastasov <ja@ssi.bg>

Re: [PATCH] ipvs: Use flexible array for MH lookup table

Posted by Julian Anastasov 5 days, 10 hours ago

	Hello,

On Mon, 18 May 2026, Rosen Penev wrote:

> Store the Maglev hash lookup table in the scheduler state
> allocation instead of allocating it separately.
> 
> This keeps the lookup table tied to the RCU-freed state lifetime and
> simplifies the allocation and cleanup paths.
> 
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  net/netfilter/ipvs/ip_vs_mh.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_mh.c b/net/netfilter/ipvs/ip_vs_mh.c
> index 020863047562..d31d3c6d4216 100644
> --- a/net/netfilter/ipvs/ip_vs_mh.c
> +++ b/net/netfilter/ipvs/ip_vs_mh.c
> @@ -59,11 +59,11 @@ static int primes[] = {251, 509, 1021, 2039, 4093,
>  
>  struct ip_vs_mh_state {
>  	struct rcu_head			rcu_head;
> -	struct ip_vs_mh_lookup		*lookup;
>  	struct ip_vs_mh_dest_setup	*dest_setup;
>  	hsiphash_key_t			hash1, hash2;
>  	int				gcd;
>  	int				rshift;
> +	struct ip_vs_mh_lookup		lookup[];
>  };
>  
>  static inline void generate_hash_secret(hsiphash_key_t *hash1,
> @@ -372,7 +372,6 @@ static void ip_vs_mh_state_free(struct rcu_head *head)

	We can even drop this function and replace it with
kfree(s) in ip_vs_mh_init_svc() and with kfree_rcu(s, rcu_head)
in ip_vs_mh_done_svc(), you can see ip_vs_dh.c for reference...

>  	struct ip_vs_mh_state *s;
>  
>  	s = container_of(head, struct ip_vs_mh_state, rcu_head);
> -	kfree(s->lookup);
>  	kfree(s);
>  }
>  
> @@ -382,16 +381,10 @@ static int ip_vs_mh_init_svc(struct ip_vs_service *svc)
>  	struct ip_vs_mh_state *s;
>  
>  	/* Allocate the MH table for this service */
> -	s = kzalloc_obj(*s);
> +	s = kzalloc_flex(*s, lookup, IP_VS_MH_TAB_SIZE);
>  	if (!s)
>  		return -ENOMEM;
>  
> -	s->lookup = kzalloc_objs(struct ip_vs_mh_lookup, IP_VS_MH_TAB_SIZE);
> -	if (!s->lookup) {
> -		kfree(s);
> -		return -ENOMEM;
> -	}
> -
>  	generate_hash_secret(&s->hash1, &s->hash2);
>  	s->gcd = ip_vs_mh_gcd_weight(svc);
>  	s->rshift = ip_vs_mh_shift_weight(svc, s->gcd);
> -- 
> 2.54.0

Regards

--
Julian Anastasov <ja@ssi.bg>