On Fri, Mar 21, 2025 at 05:14:59AM -0600, Jens Axboe wrote:

On 3/20/25 11:56 PM, Christoph Hellwig wrote:

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I don't know the entire historical context, but I presume sendmsg
did that because there was no other mechanism at the time.

At least aio had been around for about 15 years at the point, but
networking folks tend to be pretty insular and reinvent things.

Yep...

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It seems like Jens suggested that plumbing this through for splice
was a possibility, but sounds like you disagree.

Yes, very strongly.

And that is very much not what I suggested, fwiw.

Your earlier message said:

  If the answer is "because splice", then it would seem saner to
  plumb up those bits only. Would be much simpler too...

wherein I interpreted "plumb those bits" to mean plumbing the error
queue notifications on TX completions.

My sincere apologies that I misunderstood your prior message and/or
misconstrued what you said -- it was not clear to me what you meant.

It is clear to me now, though, that adding a flag to splice as
previously proposed and extending sendfile based on the SO_ZEROCOPY
sock flag being set are both unacceptable solutions.

If you happen to have a suggestion of some piece of code that I
should read (other than the iouring implementation) to inform how I
might build an RFCv2, I would appreciate the pointer.

Thanks for your time and energy,
Joe