From: John Fastabend <john.fastabend@gmail.com>
Date: Sun, 18 Mar 2018 12:57:00 -0700
Subject: net: do_tcp_sendpages flag to avoid SKBTX_SHARED_FRAG
Patch-mainline: v4.17-rc1
Git-commit: 312fc2b4c82e96a48cb2d0da2bd4816eb253c499
References: bsc#1109837
When calling do_tcp_sendpages() from in kernel and we know the data
has no references from user side we can omit SKBTX_SHARED_FRAG flag.
This patch adds an internal flag, NO_SKBTX_SHARED_FRAG that can be used
to omit setting SKBTX_SHARED_FRAG.
The flag is not exposed to userspace because the sendpage call from
the splice logic masks out all bits except MSG_MORE.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
include/linux/socket.h | 1 +
net/ipv4/tcp.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -286,6 +286,7 @@ struct ucred {
#define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */
#define MSG_BATCH 0x40000 /* sendmmsg(): more messages coming */
#define MSG_EOF MSG_FIN
+#define MSG_NO_SHARED_FRAGS 0x80000 /* sendpage() internal : page frags are not shared */
#define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */
#define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exec for file
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -966,7 +966,9 @@ new_segment:
get_page(page);
skb_fill_page_desc(skb, i, page, offset, copy);
}
- skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+
+ if (!(flags & MSG_NO_SHARED_FRAGS))
+ skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
skb->len += copy;
skb->data_len += copy;