[PATCH net-next v4 10/15] drbd: Use sendmsg(MSG_SPLICE_PAGES) rather than sendpage()

[David Howells <dhowells@xxxxxxxxxx>]

Use sendmsg() conditionally with MSG_SPLICE_PAGES in _drbd_send_page()
rather than calling sendpage() or _drbd_no_send_page().

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
cc: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
cc: "Christoph Böhmwalder" <christoph.boehmwalder@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
cc: Eric Dumazet <edumazet@xxxxxxxxxx>
cc: Jakub Kicinski <kuba@xxxxxxxxxx>
cc: Paolo Abeni <pabeni@xxxxxxxxxx>
cc: drbd-dev@xxxxxxxxxxxxxxxx
cc: linux-block@xxxxxxxxxxxxxxx
cc: netdev@xxxxxxxxxxxxxxx
---

Notes:
    ver #4)
     - Don't look at msg.msg_iter after calling sendmsg.  There's no guarantee
       it has changed.
    
    ver #2)
     - Wrap lines at 80.

 drivers/block/drbd/drbd_main.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 83987e7a5ef2..ea82d6733313 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1540,6 +1540,8 @@ static int _drbd_send_page(struct drbd_peer_device *peer_device, struct page *pa
 		    int offset, size_t size, unsigned msg_flags)
 {
 	struct socket *socket = peer_device->connection->data.socket;
+	struct msghdr msg = { .msg_flags = msg_flags, };
+	struct bio_vec bvec;
 	int len = size;
 	int err = -EIO;
 
@@ -1549,15 +1551,17 @@ static int _drbd_send_page(struct drbd_peer_device *peer_device, struct page *pa
 	 * put_page(); and would cause either a VM_BUG directly, or
 	 * __page_cache_release a page that would actually still be referenced
 	 * by someone, leading to some obscure delayed Oops somewhere else. */
-	if (drbd_disable_sendpage || !sendpage_ok(page))
-		return _drbd_no_send_page(peer_device, page, offset, size, msg_flags);
+	if (!drbd_disable_sendpage && sendpage_ok(page))
+		msg.msg_flags |= MSG_NOSIGNAL | MSG_SPLICE_PAGES;
 
-	msg_flags |= MSG_NOSIGNAL;
 	drbd_update_congested(peer_device->connection);
 	do {
 		int sent;
 
-		sent = socket->ops->sendpage(socket, page, offset, len, msg_flags);
+		bvec_set_page(&bvec, page, offset, len);
+		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, len);
+
+		sent = sock_sendmsg(socket, &msg);
 		if (sent <= 0) {
 			if (sent == -EAGAIN) {
 				if (we_should_drop_the_connection(peer_device->connection, socket))