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    Subject[PATCH net-next v3 05/18] ceph: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage
    Date
    Use sendmsg() and MSG_SPLICE_PAGES rather than sendpage in ceph when
    transmitting data. For the moment, this can only transmit one page at a
    time because of the architecture of net/ceph/, but if
    write_partial_message_data() can be given a bvec[] at a time by the
    iteration code, this would allow pages to be sent in a batch.

    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Ilya Dryomov <idryomov@gmail.com>
    cc: Xiubo Li <xiubli@redhat.com>
    cc: Jeff Layton <jlayton@kernel.org>
    cc: "David S. Miller" <davem@davemloft.net>
    cc: Eric Dumazet <edumazet@google.com>
    cc: Jakub Kicinski <kuba@kernel.org>
    cc: Paolo Abeni <pabeni@redhat.com>
    cc: Jens Axboe <axboe@kernel.dk>
    cc: Matthew Wilcox <willy@infradead.org>
    cc: ceph-devel@vger.kernel.org
    cc: netdev@vger.kernel.org
    ---
    net/ceph/messenger_v1.c | 58 ++++++++++++++---------------------------
    1 file changed, 19 insertions(+), 39 deletions(-)

    diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
    index d664cb1593a7..f082e5c780a3 100644
    --- a/net/ceph/messenger_v1.c
    +++ b/net/ceph/messenger_v1.c
    @@ -74,37 +74,6 @@ static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
    return r;
    }

    -/*
    - * @more: either or both of MSG_MORE and MSG_SENDPAGE_NOTLAST
    - */
    -static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
    - int offset, size_t size, int more)
    -{
    - ssize_t (*sendpage)(struct socket *sock, struct page *page,
    - int offset, size_t size, int flags);
    - int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
    - int ret;
    -
    - /*
    - * sendpage cannot properly handle pages with page_count == 0,
    - * we need to fall back to sendmsg if that's the case.
    - *
    - * Same goes for slab pages: skb_can_coalesce() allows
    - * coalescing neighboring slab objects into a single frag which
    - * triggers one of hardened usercopy checks.
    - */
    - if (sendpage_ok(page))
    - sendpage = sock->ops->sendpage;
    - else
    - sendpage = sock_no_sendpage;
    -
    - ret = sendpage(sock, page, offset, size, flags);
    - if (ret == -EAGAIN)
    - ret = 0;
    -
    - return ret;
    -}
    -
    static void con_out_kvec_reset(struct ceph_connection *con)
    {
    BUG_ON(con->v1.out_skip);
    @@ -464,7 +433,6 @@ static int write_partial_message_data(struct ceph_connection *con)
    struct ceph_msg *msg = con->out_msg;
    struct ceph_msg_data_cursor *cursor = &msg->cursor;
    bool do_datacrc = !ceph_test_opt(from_msgr(con->msgr), NOCRC);
    - int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
    u32 crc;

    dout("%s %p msg %p\n", __func__, con, msg);
    @@ -482,6 +450,10 @@ static int write_partial_message_data(struct ceph_connection *con)
    */
    crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
    while (cursor->total_resid) {
    + struct bio_vec bvec;
    + struct msghdr msghdr = {
    + .msg_flags = MSG_SPLICE_PAGES,
    + };
    struct page *page;
    size_t page_offset;
    size_t length;
    @@ -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;
    +
    + bvec_set_page(&bvec, page, length, page_offset);
    + iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, length);
    +
    + ret = sock_sendmsg(con->sock, &msghdr);
    if (ret <= 0) {
    if (do_datacrc)
    msg->footer.data_crc = cpu_to_le32(crc);
    @@ -526,7 +501,10 @@ static int write_partial_message_data(struct ceph_connection *con)
    */
    static int write_partial_skip(struct ceph_connection *con)
    {
    - int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
    + struct bio_vec bvec;
    + struct msghdr msghdr = {
    + .msg_flags = MSG_SPLICE_PAGES | MSG_MORE,
    + };
    int ret;

    dout("%s %p %d left\n", __func__, con, con->v1.out_skip);
    @@ -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);
    +
    + ret = sock_sendmsg(con->sock, &msghdr);
    if (ret <= 0)
    goto out;
    con->v1.out_skip -= ret;
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