Commit 2b03bcae authored by David Howells's avatar David Howells Committed by Jakub Kicinski
Browse files

kcm: Support MSG_SPLICE_PAGES 



Make AF_KCM sendmsg() support MSG_SPLICE_PAGES.  This causes pages to be
spliced from the source iterator if possible.

This allows ->sendpage() to be replaced by something that can handle
multiple multipage folios in a single transaction.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Tom Herbert <tom@herbertland.com>
cc: Tom Herbert <tom@quantonium.net>
cc: Cong Wang <cong.wang@bytedance.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 28cfea98

net/kcm/kcmsock.c

+40 −17
Original line number Diff line number Diff line
@@ -989,9 +989,29 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) 
			merge = false;

		}



		if (msg->msg_flags & MSG_SPLICE_PAGES) {

			copy = msg_data_left(msg);

			if (!sk_wmem_schedule(sk, copy))

				goto wait_for_memory;



			err = skb_splice_from_iter(skb, &msg->msg_iter, copy,

						   sk->sk_allocation);

			if (err < 0) {

				if (err == -EMSGSIZE)

					goto wait_for_memory;

				goto out_error;

			}



			copy = err;

			skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;

			sk_wmem_queued_add(sk, copy);

			sk_mem_charge(sk, copy);



			if (head != skb)

				head->truesize += copy;

		} else {

			copy = min_t(int, msg_data_left(msg),

				     pfrag->size - pfrag->offset);



			if (!sk_wmem_schedule(sk, copy))

				goto wait_for_memory;
@@ -1004,7 +1024,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) 


			/* Update the skb. */

			if (merge) {

			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);

				skb_frag_size_add(

					&skb_shinfo(skb)->frags[i - 1], copy);

			} else {

				skb_fill_page_desc(skb, i, pfrag->page,

						   pfrag->offset, copy);
@@ -1012,6 +1033,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) 
			}



			pfrag->offset += copy;

		}



		copied += copy;

		if (head != skb) {

			head->len += copy;