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net: do_tcp_sendpages flag to avoid SKBTX_SHARED_FRAG 

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>
This commit is contained in:
John Fastabend 2018-03-18 12:57:00 -07:00 committed by Daniel Borkmann
parent ffa3566001
commit 312fc2b4c8
2 changed files with 4 additions and 1 deletions
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1
include/linux/socket.h
View File

@ -287,6 +287,7 @@ 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_ZEROCOPY 0x4000000 /* Use user data in kernel path */
#define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */

4
net/ipv4/tcp.c
View File

@ -994,7 +994,9 @@ 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;