netdev - Re: nft hash set expansion problem

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Message-ID: <54D7E677.5050708@iogearbox.net>
Date:	Sun, 08 Feb 2015 23:43:03 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Josh Hunt <johunt@...mai.com>
CC:	Thomas Graf <tgraf@...g.ch>,
	Pablo Neira Ayuso <pablo@...filter.org>, kaber@...sh.net,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: nft hash set expansion problem

On 02/08/2015 08:38 PM, Josh Hunt wrote:
> Nft hash sets are unable to expand past the initial # of buckets. This is b/c nft hash sets don't define the max_shift parameter and so rht_grow_above_75():
...
> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index e96fc00..2c51617 100644
> --- a/lib/rhashtable.c
> +++ b/lib/rhashtable.c
> @@ -250,7 +250,7 @@ bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
>   {
>          /* Expand table when exceeding 75% load */
>          return atomic_read(&ht->nelems) > (new_size / 4 * 3) &&
> -              (ht->p.max_shift && atomic_read(&ht->shift) < ht->p.max_shift);
> +              (ht->p.max_shift ? atomic_read(&ht->shift) < ht->p.max_shift : 1);
>   }
>   EXPORT_SYMBOL_GPL(rht_grow_above_75);

This seems not correct as we want to have an upper limit for
rhashtable expansions. It's better to define a max_shift for
nftables, instead.
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