libceph: implement RECONNECT_SEQ feature
This is an old protocol extension that allows the client and server to
avoid resending old messages after a reconnect (following a socket error).
Instead, the exchange their sequence numbers during the handshake. This
avoids sending a bunch of useless data over the socket.
It has been supported in the server code since v0.22 (Sep 2010).
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 997dacc..e8491db 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1247,6 +1247,24 @@
}
/*
+ * Prepare to share the seq during handshake
+ */
+static void prepare_write_seq(struct ceph_connection *con)
+{
+ dout("prepare_write_seq %p %llu -> %llu\n", con,
+ con->in_seq_acked, con->in_seq);
+ con->in_seq_acked = con->in_seq;
+
+ con_out_kvec_reset(con);
+
+ con->out_temp_ack = cpu_to_le64(con->in_seq_acked);
+ con_out_kvec_add(con, sizeof (con->out_temp_ack),
+ &con->out_temp_ack);
+
+ con_flag_set(con, CON_FLAG_WRITE_PENDING);
+}
+
+/*
* Prepare to write keepalive byte.
*/
static void prepare_write_keepalive(struct ceph_connection *con)
@@ -1582,6 +1600,13 @@
con->in_base_pos = 0;
}
+static void prepare_read_seq(struct ceph_connection *con)
+{
+ dout("prepare_read_seq %p\n", con);
+ con->in_base_pos = 0;
+ con->in_tag = CEPH_MSGR_TAG_SEQ;
+}
+
static void prepare_read_tag(struct ceph_connection *con)
{
dout("prepare_read_tag %p\n", con);
@@ -2059,6 +2084,7 @@
prepare_read_connect(con);
break;
+ case CEPH_MSGR_TAG_SEQ:
case CEPH_MSGR_TAG_READY:
if (req_feat & ~server_feat) {
pr_err("%s%lld %s protocol feature mismatch,"
@@ -2089,7 +2115,12 @@
con->delay = 0; /* reset backoff memory */
- prepare_read_tag(con);
+ if (con->in_reply.tag == CEPH_MSGR_TAG_SEQ) {
+ prepare_write_seq(con);
+ prepare_read_seq(con);
+ } else {
+ prepare_read_tag(con);
+ }
break;
case CEPH_MSGR_TAG_WAIT:
@@ -2123,7 +2154,6 @@
return read_partial(con, end, size, &con->in_temp_ack);
}
-
/*
* We can finally discard anything that's been acked.
*/
@@ -2148,8 +2178,6 @@
}
-
-
static int read_partial_message_section(struct ceph_connection *con,
struct kvec *section,
unsigned int sec_len, u32 *crc)
@@ -2672,7 +2700,12 @@
prepare_read_tag(con);
goto more;
}
- if (con->in_tag == CEPH_MSGR_TAG_ACK) {
+ if (con->in_tag == CEPH_MSGR_TAG_ACK ||
+ con->in_tag == CEPH_MSGR_TAG_SEQ) {
+ /*
+ * the final handshake seq exchange is semantically
+ * equivalent to an ACK
+ */
ret = read_partial_ack(con);
if (ret <= 0)
goto out;