linux-kernel - Re: [RFC] net: esp: fix bad handling of pages from page

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Date: Wed, 6 Mar 2024 09:41:33 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: "almasrymina@...gle.com" <almasrymina@...gle.com>, "davem@...emloft.net"
 <davem@...emloft.net>, "herbert@...dor.apana.org.au"
 <herbert@...dor.apana.org.au>, Gal Pressman <gal@...dia.com>,
 "dsahern@...nel.org" <dsahern@...nel.org>, "steffen.klassert@...unet.com"
 <steffen.klassert@...unet.com>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
 Leon Romanovsky <leonro@...dia.com>, "edumazet@...gle.com"
 <edumazet@...gle.com>, "ian.kumlien@...il.com" <ian.kumlien@...il.com>,
 "Anatoli.Chechelnickiy@...nterpipe.biz"
 <Anatoli.Chechelnickiy@...nterpipe.biz>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>
Subject: Re: [RFC] net: esp: fix bad handling of pages from page_pool

On Wed, 6 Mar 2024 17:09:57 +0000 Dragos Tatulea wrote:
> > Does the caller need to check skb->pp_recycle? pp_recycle seems like a
> > redundant bit. We can tell whether the page is pp by checking
> > is_pp_page(page). the pages in the frag must be pp pages when
> > skb->pp_recycle is set and must be non pp pages when the
> > skb->pp_recycle is not set, so it all seems redundant to me.
> >   
> AFAIU we don't have to check for pp_recycle, at least not in this specific case.

Definitely not something we assuming in a fix that needs to go 
to stable.

So far, AFAIU, it's legal to have an skb without skb->pp_recycle
set, which holds full page refs to a PP page.