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    SubjectRe: [RFC PATCH v2 37/48] ceph: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage()
    From
    David,

    BTW, will this two patch depend on the others in this patch series ?

    I am planing to run a test with these two later.

    Thanks

    - Xiubo

    On 29/03/2023 22:13, David Howells wrote:
    > 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_v2.c | 89 +++++++++--------------------------------
    > 1 file changed, 18 insertions(+), 71 deletions(-)
    >
    > diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
    > index 301a991dc6a6..1637a0c21126 100644
    > --- a/net/ceph/messenger_v2.c
    > +++ b/net/ceph/messenger_v2.c
    > @@ -117,91 +117,38 @@ static int ceph_tcp_recv(struct ceph_connection *con)
    > return ret;
    > }
    >
    > -static int do_sendmsg(struct socket *sock, struct iov_iter *it)
    > -{
    > - struct msghdr msg = { .msg_flags = CEPH_MSG_FLAGS };
    > - int ret;
    > -
    > - msg.msg_iter = *it;
    > - while (iov_iter_count(it)) {
    > - ret = sock_sendmsg(sock, &msg);
    > - if (ret <= 0) {
    > - if (ret == -EAGAIN)
    > - ret = 0;
    > - return ret;
    > - }
    > -
    > - iov_iter_advance(it, ret);
    > - }
    > -
    > - WARN_ON(msg_data_left(&msg));
    > - return 1;
    > -}
    > -
    > -static int do_try_sendpage(struct socket *sock, struct iov_iter *it)
    > -{
    > - struct msghdr msg = { .msg_flags = CEPH_MSG_FLAGS };
    > - struct bio_vec bv;
    > - int ret;
    > -
    > - if (WARN_ON(!iov_iter_is_bvec(it)))
    > - return -EINVAL;
    > -
    > - while (iov_iter_count(it)) {
    > - /* iov_iter_iovec() for ITER_BVEC */
    > - bvec_set_page(&bv, it->bvec->bv_page,
    > - min(iov_iter_count(it),
    > - it->bvec->bv_len - it->iov_offset),
    > - it->bvec->bv_offset + it->iov_offset);
    > -
    > - /*
    > - * 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(bv.bv_page)) {
    > - ret = sock->ops->sendpage(sock, bv.bv_page,
    > - bv.bv_offset, bv.bv_len,
    > - CEPH_MSG_FLAGS);
    > - } else {
    > - iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bv, 1, bv.bv_len);
    > - ret = sock_sendmsg(sock, &msg);
    > - }
    > - if (ret <= 0) {
    > - if (ret == -EAGAIN)
    > - ret = 0;
    > - return ret;
    > - }
    > -
    > - iov_iter_advance(it, ret);
    > - }
    > -
    > - return 1;
    > -}
    > -
    > /*
    > * Write as much as possible. The socket is expected to be corked,
    > * so we don't bother with MSG_MORE/MSG_SENDPAGE_NOTLAST here.
    > *
    > * Return:
    > - * 1 - done, nothing (else) to write
    > + * >0 - done, nothing (else) to write
    > * 0 - socket is full, need to wait
    > * <0 - error
    > */
    > static int ceph_tcp_send(struct ceph_connection *con)
    > {
    > + struct msghdr msg = {
    > + .msg_iter = con->v2.out_iter,
    > + .msg_flags = CEPH_MSG_FLAGS,
    > + };
    > int ret;
    >
    > + if (WARN_ON(!iov_iter_is_bvec(&con->v2.out_iter)))
    > + return -EINVAL;
    > +
    > + if (con->v2.out_iter_sendpage)
    > + msg.msg_flags |= MSG_SPLICE_PAGES;
    > +
    > dout("%s con %p have %zu try_sendpage %d\n", __func__, con,
    > iov_iter_count(&con->v2.out_iter), con->v2.out_iter_sendpage);
    > - if (con->v2.out_iter_sendpage)
    > - ret = do_try_sendpage(con->sock, &con->v2.out_iter);
    > - else
    > - ret = do_sendmsg(con->sock, &con->v2.out_iter);
    > +
    > + ret = sock_sendmsg(con->sock, &msg);
    > + if (ret > 0)
    > + iov_iter_advance(&con->v2.out_iter, ret);
    > + else if (ret == -EAGAIN)
    > + ret = 0;
    > +
    > dout("%s con %p ret %d left %zu\n", __func__, con, ret,
    > iov_iter_count(&con->v2.out_iter));
    > return ret;
    >
    --
    Best Regards,

    Xiubo Li (李秀波)

    Email: xiubli@redhat.com/xiubli@ibm.com
    Slack: @Xiubo Li

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