ceph: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage()

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: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/r/20230623225513.2732256-5-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
index 301a991..87ac970 100644 (file)
--- 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.
+ * so we don't bother with MSG_MORE 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;