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Message-ID: <20240402191029.321b1609@kernel.org>
Date: Tue, 2 Apr 2024 19:10:29 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, Ayush Sawal <ayush.sawal@...lsio.com>, "David
S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
Abeni <pabeni@...hat.com>, Mirko Lindner <mlindner@...vell.com>, Stephen
Hemminger <stephen@...workplumber.org>, Tariq Toukan <tariqt@...dia.com>,
Steffen Klassert <steffen.klassert@...unet.com>, Herbert Xu
<herbert@...dor.apana.org.au>, David Ahern <dsahern@...nel.org>, Boris
Pismenny <borisp@...dia.com>, John Fastabend <john.fastabend@...il.com>,
Dragos Tatulea <dtatulea@...dia.com>, Maxim Mikityanskiy
<maxtram95@...il.com>, Sabrina Dubroca <sd@...asysnail.net>, Simon Horman
<horms@...nel.org>, Yunsheng Lin <linyunsheng@...wei.com>, "Ahelenia
ZiemiaĆska" <nabijaczleweli@...ijaczleweli.xyz>,
Christophe JAILLET <christophe.jaillet@...adoo.fr>, David Howells
<dhowells@...hat.com>, Florian Westphal <fw@...len.de>, Aleksander Lobakin
<aleksander.lobakin@...el.com>, Lorenzo Bianconi <lorenzo@...nel.org>,
Johannes Berg <johannes.berg@...el.com>, Liang Chen
<liangchen.linux@...il.com>
Subject: Re: [PATCH net-next v3 0/3] Minor cleanups to skb frag ref/unref
On Mon, 1 Apr 2024 14:50:36 -0700 Mina Almasry wrote:
> This series is largely motivated by a recent discussion where there was
> some confusion on how to properly ref/unref pp pages vs non pp pages:
>
> https://lore.kernel.org/netdev/CAHS8izOoO-EovwMwAm9tLYetwikNPxC0FKyVGu1TPJWSz4bGoA@mail.gmail.com/T/#t
>
> There is some subtely there because pp uses page->pp_ref_count for
> refcounting, while non-pp uses get_page()/put_page() for ref counting.
> Getting the refcounting pairs wrong can lead to kernel crash.
>
> Additionally currently it may not be obvious to skb users unaware of
> page pool internals how to properly acquire a ref on a pp frag. It
> requires checking of skb->pp_recycle & is_pp_page() to make the correct
> calls and may require some handling at the call site aware of arguable pp
> internals.
I concluded that Olek's series as good to go in, so you gotta rebase.
--
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