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[RFC,v2,43/48] kcm: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

Message ID 20230329141354.516864-44-dhowells@redhat.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series splice, net: Replace sendpage with sendmsg(MSG_SPLICE_PAGES) | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply, async

Commit Message

David Howells March 29, 2023, 2:13 p.m. UTC 
When transmitting data, call down into TCP using a single sendmsg with
MSG_SPLICE_PAGES to indicate that content should be spliced rather than
performing several sendmsg and sendpage calls to transmit header, data
pages and trailer.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Tom Herbert <tom@herbertland.com>
cc: Tom Herbert <tom@quantonium.net>
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
---
 net/kcm/kcmsock.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
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Patch

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index cfe828bd7fc6..819259149952 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -641,6 +641,10 @@  static int kcm_write_msgs(struct kcm_sock *kcm)
 
 		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 +655,12 @@  static int kcm_write_msgs(struct kcm_sock *kcm)
 				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