mptcp: implement wmem reservation

This leverages the previous commit to reserve the wmem
required for the sendmsg() operation when the msk socket
lock is first acquired.
Some heuristics are used to get a reasonable [over] estimation of
the whole memory required. If we can't forward alloc such amount
fallback to a reasonable small chunk, otherwise enter the wait
for memory path.

When sendmsg() needs more memory it looks at wmem_reserved
first and if that is exhausted, move more space from
sk_forward_alloc.

The reserved memory is not persistent and is released at the
next socket unlock via the release_cb().

Overall this will simplify the next patch.

Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 6abac8238de3..4cf355076e35 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -218,6 +218,7 @@ struct mptcp_sock {
 	u64		ack_seq;
 	u64		rcv_wnd_sent;
 	u64		rcv_data_fin_seq;
+	int		wmem_reserved;
 	struct sock	*last_snd;
 	int		snd_burst;
 	int		old_wspace;