linux-kernel - Re: [PATCH net v1] netmem: fix skb_frag_address

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Message-ID: <aFMxwIB2O35yfQT6@mini-arch>
Date: Wed, 18 Jun 2025 14:38:08 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, ap420073@...il.com
Subject: Re: [PATCH net v1] netmem: fix skb_frag_address_safe with unreadable
 skbs

On 06/18, Jakub Kicinski wrote:
> On Tue, 17 Jun 2025 14:52:17 -0700 Mina Almasry wrote:
> > > > Sorry, I realized right after hitting send, I'm missing:
> > > >
> > > > Fixes: 9f6b619edf2e ("net: support non paged skb frags")
> > > >
> > > > I can respin after the 24hr cooldown.  
> > >
> > > The function is used in five drivers, none of which support devmem tx,
> > > does not look like there is a reason to route it via net.
> > >
> > > The change it self looks good, but not really sure it's needed.
> > > skb_frag_address_safe is used in some pass-data-via-descriptor-ring mode,
> > > I don't see 'modern' drivers (besides bnxt which added this support in 2015)
> > > use it.  
> > 
> > Meh, a judgement call could be made here.  I've generally tried to
> > make sure skb helpers are (unreadable) netmem compatible without a
> > thorough analysis of all the callers to make sure they do or will one
> > day use (unreadable) netmem. Seems better to me to fix this before
> > some code path that plumbs unreadable memory to the helper is actually
> > merged and that code starts crashing.
> 
> Fair points, tho I prefer the simple heuristic of "can it trigger on
> net", otherwise it's really easy to waste time pondering each single
> patch. I'll apply to net-next as is. Stanislav, do you want to ack?

Sure, SG!

Acked-by: Stanislav Fomichev <sdf@...ichev.me>