From: Simon Horman <horms@kernel.org>
To: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Matt Johnston <matt@codeconstruct.com.au>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, yuanzhaoming <yuanzm2@lenovo.com>
Subject: Re: [PATCH net-next] net: mctp: avoid copy in fragmentation loop for near-MTU messages
Date: Wed, 25 Mar 2026 17:50:06 +0000 [thread overview]
Message-ID: <20260325175006.GK111839@horms.kernel.org> (raw)
In-Reply-To: <20260324-dev-mtu-copy-v1-1-7af6bd7027d3@codeconstruct.com.au>
On Tue, Mar 24, 2026 at 03:19:56PM +0800, Jeremy Kerr wrote:
> Currently, we incorrectly send messages that are within 4 bytes (a
> struct mctp_hdr) smaller than the MTU through mctp_do_fragment_route().
> This has no effect on the actual fragmentation, as we will still send as
> one packet, but unnecessarily copies the original skb into a new
> single-fragment skb.
>
> Instead of having the MTU comparisons in both mctp_local_output() and
> mctp_do_fragment_route(), feed all local messages through the latter,
> and add the single-packet optimisation there.
>
> This means we can coalesce the routing path of mctp_local_output, so our
> out_release path is now solely for errors, so rename the label
> accordingly.
>
> Include a check in the route tests for the single-packet case too.
>
> Reported-by: yuanzhaoming <yuanzm2@lenovo.com>
> Closes: https://github.com/openbmc/linux/commit/269936db5eb3962fe290b1dc4dbf1859cd5a04dd#r175836230
> Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Simon Horman <horms@kernel.org>
prev parent reply other threads:[~2026-03-25 17:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-24 7:19 [PATCH net-next] net: mctp: avoid copy in fragmentation loop for near-MTU messages Jeremy Kerr
2026-03-25 17:50 ` Simon Horman [this message]
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