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From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Alexander Aring <aahringo@redhat.com>,
	Network Development <netdev@vger.kernel.org>,
	kadlec@netfilter.org, fw@strlen.de, gfs2@lists.linux.dev,
	David Teigland <teigland@redhat.com>,
	tgraf@suug.ch
Subject: Re: nft_rhash_walk, rhashtable and resize event
Date: Mon, 18 Sep 2023 13:59:47 +0200	[thread overview]
Message-ID: <ZQg7s8MtByk4kfzP@calendula> (raw)
In-Reply-To: <ZQUjD0liUnH+ykKY@gondor.apana.org.au>

Hi Herbert,

On Sat, Sep 16, 2023 at 11:37:51AM +0800, Herbert Xu wrote:
> On Fri, Sep 15, 2023 at 10:05:06AM -0400, Alexander Aring wrote:
> >
> > My question is here? Is that allowed to do because a resize event may
> > change the order how to iterate over a rhashtable.
> 
> Walking over an rhashtable should be a last resort.  There is
> no guarantee of stability.
> 
> If you skip entries after a resize then you may miss entries.

One more question: this walk might miss entries but may it also
duplicate the same entries?

> If you want a stable walk, allocate an extra 8 bytes and use
> a linked list.

I will work on a patch to update netfilter clients for this code to
use a rcu linked list.

Thanks.

  reply	other threads:[~2023-09-18 12:00 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-15 14:05 nft_rhash_walk, rhashtable and resize event Alexander Aring
2023-09-16  3:37 ` Herbert Xu
2023-09-18 11:59   ` Pablo Neira Ayuso [this message]
2023-09-18 12:25     ` Herbert Xu
2023-09-18 12:38       ` Alexander Aring
2023-09-19  3:24         ` Herbert Xu

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