rxrpc: Do zerocopy using MSG_SPLICE_PAGES and page frags

Switch from keeping the transmission buffers in the rxrpc_txbuf struct and
allocated from the slab, to allocating them using page fragment allocators
(which uses raw pages), thereby allowing them to be passed to
MSG_SPLICE_PAGES and avoid copying into the UDP buffers.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
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: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org

1 files changed, 5 insertions, 17 deletions

diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 1e81046ea8a6..4d152f06b039 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -336,7 +336,7 @@ reload:
 
 	do {
 		if (!txb) {
-			size_t remain, bufsize, chunk, offset;
+			size_t remain;
 
 			_debug("alloc");
 
@@ -348,23 +348,11 @@ reload:
 			 * region (enc blocksize), but the trailer is not.
 			 */
 			remain = more ? INT_MAX : msg_data_left(msg);
-			ret = call->conn->security->how_much_data(call, remain,
-								  &bufsize, &chunk, &offset);
-			if (ret < 0)
-				goto maybe_error;
-
-			_debug("SIZE: %zu/%zu @%zu", chunk, bufsize, offset);
-
-			/* create a buffer that we can retain until it's ACK'd */
-			ret = -ENOMEM;
-			txb = rxrpc_alloc_txbuf(call, RXRPC_PACKET_TYPE_DATA,
-						GFP_KERNEL);
-			if (!txb)
+			txb = call->conn->security->alloc_txbuf(call, remain, sk->sk_allocation);
+			if (IS_ERR(txb)) {
+				ret = PTR_ERR(txb);
 				goto maybe_error;
-
-			txb->offset = offset + sizeof(struct rxrpc_wire_header);
-			txb->space -= offset;
-			txb->space = min_t(size_t, chunk, txb->space);
+			}
 		}
 
 		_debug("append");