Re: [PATCH net-next v2] net: dsa: Fix skb ownership in taggers

[Vladimir Oltean <olteanv@gmail.com>]

On Wed, Jun 17, 2026 at 02:23:40PM +0200, Linus Walleij wrote:
> > - Has anyone proven that a real problem exists? Because dsa_user_xmit()
> >   -> skb_ensure_writable_head_tail() has run successfully at this stage,
> >   so we know that dev->needed_headroom bytes are available for writing.
> >   Because DSA uses VLAN as a tag, dsa_user_setup_tagger() will increase
> >   dev->needed_headroom by VLAN_HLEN for the tag_8021q protocols, so
> >   vlan_insert_tag() should not fail. I've looked at this function at it
> >   seems not to be coded up to fail for any other reason.
> 
> I guess what you're saying is that vlan_insert_tag() will never fail in
> ->xmit()?

Yes, I may be wrong, but this is what I think. The central idea of the
generic TX reallocation series
(https://lore.kernel.org/netdev/20201030014910.2738809-1-vladimir.oltean@nxp.com/)
was to simplify taggers by moving the failure point in case of
reallocation somewhere else. I'm just saying I don't see a strong reason
to complicate the tagger responsibility again.