netdev - Re: [RFC PATCH] net: Fix one page_pool page leak from skb_frag

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Message-ID: <20240426160859.0d85908e@kernel.org>
Date: Fri, 26 Apr 2024 16:08:59 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: Dragos Tatulea <dtatulea@...dia.com>, "davem@...emloft.net"
 <davem@...emloft.net>, "pabeni@...hat.com" <pabeni@...hat.com>,
 "ilias.apalodimas@...aro.org" <ilias.apalodimas@...aro.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "jacob.e.keller@...el.com" <jacob.e.keller@...el.com>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Jianbo Liu
 <jianbol@...dia.com>, "edumazet@...gle.com" <edumazet@...gle.com>
Subject: Re: [RFC PATCH] net: Fix one page_pool page leak from
 skb_frag_unref

On Thu, 25 Apr 2024 12:20:59 -0700 Mina Almasry wrote:
> -       if (recycle && napi_pp_get_page(page))
> +       if (napi_pp_get_page(page))

Pretty sure you can't do that. The "recycle" here is a concurrency
guarantee. A guarantee someone is holding a pp ref on that page,
a ref which will not go away while napi_pp_get_page() is executing.