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Date: Fri, 16 Feb 2024 18:47:33 +0100
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Subject: Re: [PATCH net-next] page_pool: disable direct recycling based on
 pool->cpuid on destroy
To: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>, Lorenzo Bianconi <lorenzo@kernel.org>,
	=?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>,
	<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20240215113905.96817-1-aleksander.lobakin@intel.com>
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From: Alexander Lobakin <aleksander.lobakin@intel.com>
In-Reply-To: <20240215113905.96817-1-aleksander.lobakin@intel.com>
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From: Alexander Lobakin <aleksander.lobakin@intel.com>
Date: Thu, 15 Feb 2024 12:39:05 +0100

> Now that direct recycling is performed basing on pool->cpuid when set,
> memory leaks are possible:
> 
> 1. A pool is destroyed.
> 2. Alloc cache is emptied (it's done only once).
> 3. pool->cpuid is still set.
> 4. napi_pp_put_page() does direct recycling basing on pool->cpuid.
> 5. Now alloc cache is not empty, but it won't ever be freed.
> 
> In order to avoid that, rewrite pool->cpuid to -1 when unlinking NAPI to
> make sure no direct recycling will be possible after emptying the cache.
> This involves a bit of overhead as pool->cpuid now must be accessed
> via READ_ONCE() to avoid partial reads.
> Rename page_pool_unlink_napi() -> page_pool_disable_direct_recycling()
> to reflect what it actually does and unexport it.

PW says "Changes requested", but I don't see any in the thread, did I
miss something? :D

Thanks,
Olek