chelsio: Support MSG_SPLICE_PAGES

Make Chelsio's TLS offload sendmsg() support MSG_SPLICE_PAGES, splicing in
pages from the source iterator if possible and copying the data in
otherwise.

This allows ->sendpage() to be replaced by something that can handle
multiple multipage folios in a single transaction.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Ayush Sawal <ayush.sawal@chelsio.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: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: netdev@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_io.c

@@ -1092,7 +1092,17 @@ int chtls_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 		if (copy > size)
 			copy = size;
 
-		if (skb_tailroom(skb) > 0) {
+		if (msg->msg_flags & MSG_SPLICE_PAGES) {
+			err = skb_splice_from_iter(skb, &msg->msg_iter, copy,
+						   sk->sk_allocation);
+			if (err < 0) {
+				if (err == -EMSGSIZE)
+					goto new_buf;
+				goto do_fault;
+			}
+			copy = err;
+			sk_wmem_queued_add(sk, copy);
+		} else if (skb_tailroom(skb) > 0) {
 			copy = min(copy, skb_tailroom(skb));
 			if (is_tls_tx(csk))
 				copy = min_t(int, copy, csk->tlshws.txleft);