linux-kernel - Re: [PATCH net-next v4 03/15] ceph: Use sendmsg(MSG_SPLICE

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Date:   Fri, 23 Jun 2023 10:00:40 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     netdev@...r.kernel.org,
        Alexander Duyck <alexander.duyck@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Ilya Dryomov <idryomov@...il.com>,
        Xiubo Li <xiubli@...hat.com>, Jeff Layton <jlayton@...nel.org>,
        ceph-devel@...r.kernel.org
Subject: Re: [PATCH net-next v4 03/15] ceph: Use sendmsg(MSG_SPLICE_PAGES)
 rather than sendpage

On Fri, 23 Jun 2023 12:44:13 +0100 David Howells wrote:
> @@ -494,9 +466,12 @@ static int write_partial_message_data(struct ceph_connection *con)
>  
>  		page = ceph_msg_data_next(cursor, &page_offset, &length);
>  		if (length == cursor->total_resid)
> -			more = MSG_MORE;
> -		ret = ceph_tcp_sendpage(con->sock, page, page_offset, length,
> -					more);
> +			msghdr.msg_flags |= MSG_MORE;

Should the condition also be flipped here, like you did below?
(can be a follow up if so)

> @@ -534,9 +512,11 @@ static int write_partial_skip(struct ceph_connection *con)
>  		size_t size = min(con->v1.out_skip, (int)PAGE_SIZE);
>  
>  		if (size == con->v1.out_skip)
> -			more = MSG_MORE;
> -		ret = ceph_tcp_sendpage(con->sock, ceph_zero_page, 0, size,
> -					more);
> +			msghdr.msg_flags &= ~MSG_MORE;
> +		bvec_set_page(&bvec, ZERO_PAGE(0), size, 0);
> +		iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, size);