On 03/19/2013 05:48 PM, Sage Weil wrote:
> 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).
OK, a few comments below, but this looks good to me.
Make the suggested (or implied) changes below if you
like, but either way:
Reviewed-by: Alex Elder <elder@xxxxxxxxxxx>
> Signed-off-by: Sage Weil <sage@xxxxxxxxxxx>
> ---
> include/linux/ceph/ceph_features.h | 2 ++
> include/linux/ceph/msgr.h | 1 +
> net/ceph/messenger.c | 47 +++++++++++++++++++++++++++++++++---
> 3 files changed, 46 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/ceph/ceph_features.h b/include/linux/ceph/ceph_features.h
> index 76554ce..4c420803 100644
> --- a/include/linux/ceph/ceph_features.h
> +++ b/include/linux/ceph/ceph_features.h
> @@ -41,6 +41,7 @@
> */
> #define CEPH_FEATURES_SUPPORTED_DEFAULT \
> (CEPH_FEATURE_NOSRCADDR | \
> + CEPH_FEATURE_RECONNECT_SEQ | \
> CEPH_FEATURE_PGID64 | \
> CEPH_FEATURE_PGPOOL3 | \
> CEPH_FEATURE_OSDENC | \
> @@ -51,6 +52,7 @@
>
> #define CEPH_FEATURES_REQUIRED_DEFAULT \
> (CEPH_FEATURE_NOSRCADDR | \
> + CEPH_FEATURE_RECONNECT_SEQ | \
> CEPH_FEATURE_PGID64 | \
> CEPH_FEATURE_PGPOOL3 | \
> CEPH_FEATURE_OSDENC)
Is it really a required feature?
If the other end doesn't support it is there any
reason we can't fall back to the old behavior?
This code is only *responding* to a SEQ tag, it doesn't
initiate one. If one is never sent by the server the
behavior remains correct, just slower.
I also have two points you might help clarify for me:
- Is this a server initiated feature, or could a client
send it?
- Because it's a tagged bit of message data it really
could occur at any time--though at the end of a
reconnect negotiation is where it's valuable. Correct?
> diff --git a/include/linux/ceph/msgr.h b/include/linux/ceph/msgr.h
> index 680d3d6..3d94a73 100644
> --- a/include/linux/ceph/msgr.h
> +++ b/include/linux/ceph/msgr.h
> @@ -87,6 +87,7 @@ struct ceph_entity_inst {
> #define CEPH_MSGR_TAG_BADPROTOVER 10 /* bad protocol version */
> #define CEPH_MSGR_TAG_BADAUTHORIZER 11 /* bad authorizer */
> #define CEPH_MSGR_TAG_FEATURES 12 /* insufficient features */
> +#define CEPH_MSGR_TAG_SEQ 13 /* 64-bit int follows with seen seq number */
>
>
> /*
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 997dacc..2bf2806 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -1247,6 +1247,24 @@ static void prepare_write_ack(struct ceph_connection *con)
> }
>
> /*
> + * 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 @@ static void prepare_read_ack(struct ceph_connection *con)
> 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 @@ static int process_connect(struct ceph_connection *con)
> 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 @@ static int process_connect(struct ceph_connection *con)
>
> 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 @@ static int read_partial_ack(struct ceph_connection *con)
> return read_partial(con, end, size, &con->in_temp_ack);
> }
>
> -
> /*
> * We can finally discard anything that's been acked.
> */
> @@ -2148,8 +2178,6 @@ static void process_ack(struct ceph_connection *con)
> }
>
>
> -
> -
> static int read_partial_message_section(struct ceph_connection *con,
> struct kvec *section,
> unsigned int sec_len, u32 *crc)
> @@ -2628,6 +2656,17 @@ more:
> if (con->in_base_pos)
> goto more;
> }
> + if (con->in_tag == CEPH_MSGR_TAG_SEQ) {
> + /*
> + * the final seq exchange is semantically equivalent
> + * to an ACK; re-use those helpers.
> + */
> + ret = read_partial_ack(con);
> + if (ret <= 0)
> + goto out;
> + process_ack(con);
> + goto more;
> + }
This block (above) is identical to the block a little later on
that handles CEPH_MSGR_TAG_ACK. It might be nice to make that
fact obvious by combining them (and if so, I would say here, not
below). (It's OK as-is, however.)
> if (con->in_tag == CEPH_MSGR_TAG_READY) {
> /*
> * what's next?
>
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