[PATCH 06/11] drbd: Runtime changeable wire protocol

From: Philipp Reisner
Date: Fri Sep 30 2011 - 08:49:56 EST

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The wire protocol is no longer a property that is negotiated
between the two peers. It is now expressed with two bits
(DP_SEND_WRITE_ACK and DP_SEND_RECEIVE_ACK) in each data
packet. Therefore the primary node is free to change the
wire protocol at any time without disconnect/reconnect.

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_int.h | 6 +++++
drivers/block/drbd/drbd_main.c | 8 ++++++-
drivers/block/drbd/drbd_receiver.c | 39 +++++++++++++++++------------------
drivers/block/drbd/drbd_req.c | 18 ++++++++++++----
drivers/block/drbd/drbd_req.h | 8 +++++++
5 files changed, 53 insertions(+), 26 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 2119d9b..c57cedb 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -327,6 +327,8 @@ extern unsigned int drbd_header_size(struct drbd_tconn *tconn);
#define DP_FUA 16 /* equals REQ_FUA */
#define DP_FLUSH 32 /* equals REQ_FLUSH */
#define DP_DISCARD 64 /* equals REQ_DISCARD */
+#define DP_SEND_RECEIVE_ACK 128 /* This is a proto B write request */
+#define DP_SEND_WRITE_ACK 256 /* This is a proto C write request */

struct p_data {
u64 sector; /* 64 bits sector number */
@@ -656,6 +658,9 @@ enum {

/* Conflicting local requests need to be restarted after this request */
__EE_RESTART_REQUESTS,
+
+ /* The peer wants a write ACK for this (wire proto C) */
+ __EE_SEND_WRITE_ACK,
};
#define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
#define EE_MAY_SET_IN_SYNC (1<<__EE_MAY_SET_IN_SYNC)
@@ -663,6 +668,7 @@ enum {
#define EE_WAS_ERROR (1<<__EE_WAS_ERROR)
#define EE_HAS_DIGEST (1<<__EE_HAS_DIGEST)
#define EE_RESTART_REQUESTS (1<<__EE_RESTART_REQUESTS)
+#define EE_SEND_WRITE_ACK (1<<__EE_SEND_WRITE_ACK)

/* flag bits per mdev */
enum {
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index a2cac15..6a11e9d 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1672,6 +1672,12 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
if (mdev->state.conn >= C_SYNC_SOURCE &&
mdev->state.conn <= C_PAUSED_SYNC_T)
dp_flags |= DP_MAY_SET_IN_SYNC;
+ if (mdev->tconn->agreed_pro_version >= 100) {
+ if (req->rq_state & RQ_EXP_RECEIVE_ACK)
+ dp_flags |= DP_SEND_RECEIVE_ACK;
+ if (req->rq_state & RQ_EXP_WRITE_ACK)
+ dp_flags |= DP_SEND_WRITE_ACK;
+ }
p->dp_flags = cpu_to_be32(dp_flags);
if (dgs)
drbd_csum_bio(mdev, mdev->tconn->integrity_w_tfm, req->master_bio, p + 1);
@@ -1688,7 +1694,7 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
* out ok after sending on this side, but does not fit on the
* receiving side, we sure have detected corruption elsewhere.
*/
- if (mdev->tconn->net_conf->wire_protocol == DRBD_PROT_A || dgs)
+ if (!(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK)) || dgs)
err = _drbd_send_bio(mdev, req->master_bio);
else
err = _drbd_send_zc_bio(mdev, req->master_bio);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 4d9d71a..0b648dc 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1697,7 +1697,7 @@ static int e_end_block(struct drbd_work *w, int cancel)
sector_t sector = peer_req->i.sector;
int err = 0, pcmd;

- if (mdev->tconn->net_conf->wire_protocol == DRBD_PROT_C) {
+ if (peer_req->flags & EE_SEND_WRITE_ACK) {
if (likely((peer_req->flags & EE_WAS_ERROR) == 0)) {
pcmd = (mdev->state.conn >= C_SYNC_SOURCE &&
mdev->state.conn <= C_PAUSED_SYNC_T &&
@@ -2074,20 +2074,28 @@ static int receive_Data(struct drbd_tconn *tconn, struct packet_info *pi)
list_add(&peer_req->w.list, &mdev->active_ee);
spin_unlock_irq(&mdev->tconn->req_lock);

- switch (mdev->tconn->net_conf->wire_protocol) {
- case DRBD_PROT_C:
+ if (mdev->tconn->agreed_pro_version < 100) {
+ switch (mdev->tconn->net_conf->wire_protocol) {
+ case DRBD_PROT_C:
+ dp_flags |= DP_SEND_WRITE_ACK;
+ break;
+ case DRBD_PROT_B:
+ dp_flags |= DP_SEND_RECEIVE_ACK;
+ break;
+ }
+ }
+
+ if (dp_flags & DP_SEND_WRITE_ACK) {
+ peer_req->flags |= EE_SEND_WRITE_ACK;
inc_unacked(mdev);
/* corresponding dec_unacked() in e_end_block()
* respective _drbd_clear_done_ee */
- break;
- case DRBD_PROT_B:
+ }
+
+ if (dp_flags & DP_SEND_RECEIVE_ACK) {
/* I really don't like it that the receiver thread
* sends on the msock, but anyways */
drbd_send_ack(mdev, P_RECV_ACK, peer_req);
- break;
- case DRBD_PROT_A:
- /* nothing to do */
- break;
}

if (mdev->state.pdsk < D_INCONSISTENT) {
@@ -2932,7 +2940,7 @@ static int receive_protocol(struct drbd_tconn *tconn, struct packet_info *pi)
if (cf & CF_DRY_RUN)
set_bit(CONN_DRY_RUN, &tconn->flags);

- if (p_proto != tconn->net_conf->wire_protocol) {
+ if (p_proto != tconn->net_conf->wire_protocol && tconn->agreed_pro_version < 100) {
conn_err(tconn, "incompatible communication protocols\n");
goto disconnect;
}
@@ -4622,23 +4630,18 @@ static int got_BlockAck(struct drbd_tconn *tconn, struct packet_info *pi)
}
switch (pi->cmd) {
case P_RS_WRITE_ACK:
- D_ASSERT(mdev->tconn->net_conf->wire_protocol == DRBD_PROT_C);
what = WRITE_ACKED_BY_PEER_AND_SIS;
break;
case P_WRITE_ACK:
- D_ASSERT(mdev->tconn->net_conf->wire_protocol == DRBD_PROT_C);
what = WRITE_ACKED_BY_PEER;
break;
case P_RECV_ACK:
- D_ASSERT(mdev->tconn->net_conf->wire_protocol == DRBD_PROT_B);
what = RECV_ACKED_BY_PEER;
break;
case P_DISCARD_WRITE:
- D_ASSERT(mdev->tconn->net_conf->wire_protocol == DRBD_PROT_C);
what = DISCARD_WRITE;
break;
case P_RETRY_WRITE:
- D_ASSERT(mdev->tconn->net_conf->wire_protocol == DRBD_PROT_C);
what = POSTPONE_WRITE;
break;
default:
@@ -4656,8 +4659,6 @@ static int got_NegAck(struct drbd_tconn *tconn, struct packet_info *pi)
struct p_block_ack *p = pi->data;
sector_t sector = be64_to_cpu(p->sector);
int size = be32_to_cpu(p->blksize);
- bool missing_ok = tconn->net_conf->wire_protocol == DRBD_PROT_A ||
- tconn->net_conf->wire_protocol == DRBD_PROT_B;
int err;

mdev = vnr_to_mdev(tconn, pi->vnr);
@@ -4674,15 +4675,13 @@ static int got_NegAck(struct drbd_tconn *tconn, struct packet_info *pi)

err = validate_req_change_req_state(mdev, p->block_id, sector,
&mdev->write_requests, __func__,
- NEG_ACKED, missing_ok);
+ NEG_ACKED, true);
if (err) {
/* Protocol A has no P_WRITE_ACKs, but has P_NEG_ACKs.
The master bio might already be completed, therefore the
request is no longer in the collision hash. */
/* In Protocol B we might already have got a P_RECV_ACK
but then get a P_NEG_ACK afterwards. */
- if (!missing_ok)
- return err;
drbd_set_out_of_sync(mdev, sector, size);
}
return 0;
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index fd0b452..0f1a29f 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -323,7 +323,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
struct bio_and_error *m)
{
struct drbd_conf *mdev = req->w.mdev;
- int rv = 0;
+ int p, rv = 0;

if (m)
m->bio = NULL;
@@ -344,6 +344,10 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
* and from w_read_retry_remote */
D_ASSERT(!(req->rq_state & RQ_NET_MASK));
req->rq_state |= RQ_NET_PENDING;
+ p = mdev->tconn->net_conf->wire_protocol;
+ req->rq_state |=
+ p == DRBD_PROT_C ? RQ_EXP_WRITE_ACK :
+ p == DRBD_PROT_B ? RQ_EXP_RECEIVE_ACK : 0;
inc_ap_pending(mdev);
break;

@@ -500,7 +504,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
atomic_add(req->i.size >> 9, &mdev->ap_in_flight);

if (bio_data_dir(req->master_bio) == WRITE &&
- mdev->tconn->net_conf->wire_protocol == DRBD_PROT_A) {
+ !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
/* this is what is dangerous about protocol A:
* pretend it was successfully written on the peer. */
if (req->rq_state & RQ_NET_PENDING) {
@@ -550,6 +554,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
req->rq_state |= RQ_NET_DONE;
/* fall through */
case WRITE_ACKED_BY_PEER:
+ D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
/* protocol C; successfully written on peer.
* Nothing to do here.
* We want to keep the tl in place for all protocols, to cater
@@ -560,11 +565,14 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
* request could set NET_DONE right here, and not wait for the
* P_BARRIER_ACK, but that is an unnecessary optimization. */

+ goto ack_common;
/* this makes it effectively the same as for: */
case RECV_ACKED_BY_PEER:
+ D_ASSERT(req->rq_state & RQ_EXP_RECEIVE_ACK);
/* protocol B; pretends to be successfully written on peer.
* see also notes above in HANDED_OVER_TO_NETWORK about
* protocol != C */
+ ack_common:
req->rq_state |= RQ_NET_OK;
D_ASSERT(req->rq_state & RQ_NET_PENDING);
dec_ap_pending(mdev);
@@ -574,8 +582,8 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
break;

case POSTPONE_WRITE:
- /*
- * If this node has already detected the write conflict, the
+ D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
+ /* If this node has already detected the write conflict, the
* worker will be waiting on misc_wait. Wake it up once this
* request has completed locally.
*/
@@ -646,7 +654,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
}
if ((req->rq_state & RQ_NET_MASK) != 0) {
req->rq_state |= RQ_NET_DONE;
- if (mdev->tconn->net_conf->wire_protocol == DRBD_PROT_A)
+ if (!(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK)))
atomic_sub(req->i.size>>9, &mdev->ap_in_flight);
}
_req_may_be_done(req, m); /* Allowed while state.susp */
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index b9f474a..dfd2cef 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -198,6 +198,12 @@ enum drbd_req_state_bits {

/* The peer has sent a retry ACK */
__RQ_POSTPONED,
+
+ /* We expect a receive ACK (wire proto B) */
+ __RQ_EXP_RECEIVE_ACK,
+
+ /* We expect a write ACK (wite proto C) */
+ __RQ_EXP_WRITE_ACK,
};

#define RQ_LOCAL_PENDING (1UL << __RQ_LOCAL_PENDING)
@@ -219,6 +225,8 @@ enum drbd_req_state_bits {
#define RQ_WRITE (1UL << __RQ_WRITE)
#define RQ_IN_ACT_LOG (1UL << __RQ_IN_ACT_LOG)
#define RQ_POSTPONED (1UL << __RQ_POSTPONED)
+#define RQ_EXP_RECEIVE_ACK (1UL << __RQ_EXP_RECEIVE_ACK)
+#define RQ_EXP_WRITE_ACK (1UL << __RQ_EXP_WRITE_ACK)

/* For waking up the frozen transfer log mod_req() has to return if the request
should be counted in the epoch object*/
--
1.7.4.1

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