netdev - Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred expansion/shrinking

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Date:	Fri, 16 Jan 2015 15:34:16 +0000
From:	Patrick McHardy <kaber@...sh.net>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	kernel@...r.kernel.org, herbert@...dor.apana.org.au,
	paulmck@...ux.vnet.ibm.com, edumazet@...gle.com,
	john.r.fastabend@...el.com, josh@...htriplett.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred
 expansion/shrinking

On 15.12, Thomas Graf wrote:
> The patch also defers expansion and shrinking to a worker queue which
> allows insertion and removal from atomic context. Insertions and
> deletions may occur in parallel to it and are only held up briefly
> while the particular bucket is linked or unzipped.
>
> Mutations of the bucket table pointer is protected by a new mutex, read
> access is RCU protected.
> 
> In the event of an expansion or shrinking, the new bucket table allocated
> is exposed as a so called future table as soon as the resize process
> starts.  Lookups, deletions, and insertions will briefly use both tables.
> The future table becomes the main table after an RCU grace period and
> initial linking of the old to the new table was performed. Optimization
> of the chains to make use of the new number of buckets follows only the
> new table is in use.

AFAICT nft_hash_walk() will miss new entries during this period.
Am I missing anything here?
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