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Date:   Wed, 7 Jun 2023 09:55:41 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     David Howells <dhowells@redhat.com>
Cc:     netdev@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        Boris Pismenny <borisp@nvidia.com>,
        John Fastabend <john.fastabend@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        David Ahern <dsahern@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next v5 03/14] splice, net: Use
 sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()
Message-ID: <20230607095541.586a3300@kernel.org>
In-Reply-To: <20230607140559.2263470-4-dhowells@redhat.com>
References: <20230607140559.2263470-1-dhowells@redhat.com>
        <20230607140559.2263470-4-dhowells@redhat.com>
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On Wed,  7 Jun 2023 15:05:48 +0100 David Howells wrote:
> Replace generic_splice_sendpage() + splice_from_pipe + pipe_to_sendpage()
> with a net-specific handler, splice_to_socket(), that calls sendmsg() with
> MSG_SPLICE_PAGES set instead of calling ->sendpage().
> 
> MSG_MORE is used to indicate if the sendmsg() is expected to be followed
> with more data.
> 
> This allows multiple pipe-buffer pages to be passed in a single call in a
> BVEC iterator, allowing the processing to be pushed down to a loop in the
> protocol driver.  This helps pave the way for passing multipage folios down
> too.
> 
> Protocols that haven't been converted to handle MSG_SPLICE_PAGES yet should
> just ignore it and do a normal sendmsg() for now - although that may be a
> bit slower as it may copy everything.

Reviewed-by: Jakub Kicinski <kuba@kernel.org>