smb: smbdirect: introduce smbdirect_socket.recv_io.free.{list,lock}

This will allow the list of free smbdirect_recv_io messages including
the spinlock to be in common between client and server in order
to split out common helper functions in future.

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/common/smbdirect/smbdirect_socket.h

@@ -51,6 +51,15 @@ struct smbdirect_socket {
 			SMBDIRECT_EXPECT_NEGOTIATE_REP = 2,
 			SMBDIRECT_EXPECT_DATA_TRANSFER = 3,
 		} expected;
+
+		/*
+		 * The list of free smbdirect_recv_io
+		 * structures
+		 */
+		struct {
+			struct list_head list;
+			spinlock_t lock;
+		} free;
 	} recv_io;
 };