[RFC PATCH 01/28] net: Declare MSG_SPLICE_PAGES internal sendmsg() flag

[David Howells <dhowells@redhat.com>]

Declare MSG_SPLICE_PAGES, an internal sendmsg() flag, that hints to a
network protocol that it should splice pages from the source iterator
rather than copying the data if it can.

This is intended as a replacement for the ->sendpage() op, allowing a way
to splice in several multipage folios in one go.

Signed-off-by: David Howells <dhowells@redhat.com>
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
---
 include/linux/socket.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 13c3a237b9c9..a67d02da3c54 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -327,6 +327,7 @@ struct ucred {
 					  */
 
 #define MSG_ZEROCOPY	0x4000000	/* Use user data in kernel path */
+#define MSG_SPLICE_PAGES 0x8000000	/* Splice the pages from the iterator in sendmsg() */
 #define MSG_FASTOPEN	0x20000000	/* Send data in TCP SYN */
 #define MSG_CMSG_CLOEXEC 0x40000000	/* Set close_on_exec for file
 					   descriptor received through