netdev - Re: [PATCH V2 net-next 4/7] rds: support for zcopy completion notification

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Date:   Thu, 15 Feb 2018 11:35:27 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, rds-devel@....oracle.com,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>
Subject: Re: [PATCH V2 net-next 4/7] rds: support for zcopy completion notification

On Thu, Feb 15, 2018 at 7:03 AM, Sowmini Varadhan
<sowmini.varadhan@...cle.com> wrote:
> On (02/14/18 19:41), Willem de Bruijn wrote:
>>
>> One more thing: this code notifies that the operation succeeded, but
>> the data was copied in the process. It does not have to be set otherwise.
>
> I see. this one was a bit confusing for me (hence the copy/paste) -
> maybe because the TCP/UDP/PACKET case is a bit different from RDS,
> and sendmsg may find that it has to switch from zcopy to bcopy
> after the sendmsg() itself has returned, but this cannot happen
> for RDS (thus I should never set this code?).

Agreed.

> Is it ok if I fix this in the next round or do you think
> this warrants a V3?

The flag is a hint, so on its own it does not require a respin.

There are by now four small items to patch up. I would respin so that the
patchset that is recorded can be read later as a single correct solution.

But either way works, I don't feel strongly.