kcm: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

When transmitting data, call down into the transport socket using sendmsg
with MSG_SPLICE_PAGES to indicate that content should be spliced rather
than using sendpage.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Tom Herbert <tom@herbertland.com>
cc: Tom Herbert <tom@quantonium.net>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 7dee744..3bcac14 100644 (file)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -641,6 +641,10 @@ do_frag_list:
 
                for (fragidx = 0; fragidx < skb_shinfo(skb)->nr_frags;
                     fragidx++) {
+                       struct bio_vec bvec;
+                       struct msghdr msg = {
+                               .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES,
+                       };
                        skb_frag_t *frag;
 
                        frag_offset = 0;
@@ -651,11 +655,13 @@ do_frag:
                                goto out;
                        }
 
-                       ret = kernel_sendpage(psock->sk->sk_socket,
-                                             skb_frag_page(frag),
-                                             skb_frag_off(frag) + frag_offset,
-                                             skb_frag_size(frag) - frag_offset,
-                                             MSG_DONTWAIT);
+                       bvec_set_page(&bvec,
+                                     skb_frag_page(frag),
+                                     skb_frag_size(frag) - frag_offset,
+                                     skb_frag_off(frag) + frag_offset);
+                       iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1,
+                                     bvec.bv_len);
+                       ret = sock_sendmsg(psock->sk->sk_socket, &msg);
                        if (ret <= 0) {
                                if (ret == -EAGAIN) {
                                        /* Save state to try again when there's