[PATCH net-next v5 15/19] ip6, udp6: Support MSG_SPLICE_PAGES

From: David Howells
Date: Thu Apr 06 2023 - 05:46:52 EST


Make IP6/UDP6 sendmsg() support MSG_SPLICE_PAGES. This causes pages to be
spliced from the source iterator if possible, copying the data if not.

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

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>
cc: David Ahern <dsahern@xxxxxxxxxx>
cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
cc: Eric Dumazet <edumazet@xxxxxxxxxx>
cc: Jakub Kicinski <kuba@xxxxxxxxxx>
cc: Paolo Abeni <pabeni@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: netdev@xxxxxxxxxxxxxxx
---
include/net/ip.h | 1 +
net/ipv4/ip_output.c | 4 ++--
net/ipv6/ip6_output.c | 12 ++++++++++++
3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index c3fffaa92d6e..dcbedeffab60 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -211,6 +211,7 @@ int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb);
int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
__u8 tos);
void ip_init(void);
+int __ip_splice_pages(struct sock *sk, struct sk_buff *skb, void *from, int *pcopy);
int ip_append_data(struct sock *sk, struct flowi4 *fl4,
int getfrag(void *from, char *to, int offset, int len,
int odd, struct sk_buff *skb),
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 48db7bf475df..5b66c28c2e41 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -960,8 +960,7 @@ csum_page(struct page *page, int offset, int copy)
/*
* Add (or copy) data pages for MSG_SPLICE_PAGES.
*/
-static int __ip_splice_pages(struct sock *sk, struct sk_buff *skb,
- void *from, int *pcopy)
+int __ip_splice_pages(struct sock *sk, struct sk_buff *skb, void *from, int *pcopy)
{
struct msghdr *msg = from;
struct page *page = NULL, **pages = &page;
@@ -1010,6 +1009,7 @@ static int __ip_splice_pages(struct sock *sk, struct sk_buff *skb,
*pcopy = copy;
return 0;
}
+EXPORT_SYMBOL_GPL(__ip_splice_pages);

static int __ip_append_data(struct sock *sk,
struct flowi4 *fl4,
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 0b6140f0179d..82846d18cf22 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1589,6 +1589,14 @@ static int __ip6_append_data(struct sock *sk,
skb_zcopy_set(skb, uarg, &extra_uref);
}
}
+ } else if ((flags & MSG_SPLICE_PAGES) && length) {
+ if (inet_sk(sk)->hdrincl)
+ return -EPERM;
+ if (rt->dst.dev->features & NETIF_F_SG)
+ /* We need an empty buffer to attach stuff to */
+ paged = true;
+ else
+ flags &= ~MSG_SPLICE_PAGES;
}

/*
@@ -1778,6 +1786,10 @@ static int __ip6_append_data(struct sock *sk,
err = -EFAULT;
goto error;
}
+ } else if (flags & MSG_SPLICE_PAGES) {
+ err = __ip_splice_pages(sk, skb, from, &copy);
+ if (err < 0)
+ goto error;
} else if (!zc) {
int i = skb_shinfo(skb)->nr_frags;