Merge branch 'splice-net-handle-msg_splice_pages-in-af_kcm'

Merge branch 'splice-net-handle-msg_splice_pages-in-af_kcm'

David Howells says:

====================
splice, net: Handle MSG_SPLICE_PAGES in AF_KCM

Here are patches to make AF_KCM handle the MSG_SPLICE_PAGES internal
sendmsg flag.  MSG_SPLICE_PAGES is an internal hint that tells the protocol
that it should splice the pages supplied if it can.  Its sendpage
implementation is then turned into a wrapper around that.

Does anyone actually use AF_KCM?  Upstream it has some issues.  It doesn't
seem able to handle a "message" longer than 113920 bytes without jamming
and doesn't handle the client termination once it is jammed.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=51c78a4d532efe9543a4df019ff405f05c6157f6
Link: https://lore.kernel.org/r/20230524144923.3623536-1-dhowells@redhat.com/
====================

Link: https://lore.kernel.org/r/20230531110423.643196-1-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>