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drbd: send intermediate state change results to the peer
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DRBD state changes schedule after_state_ch() actions to a worker thread,
which decides on the old and new states of that change, whether to send
an informational state update packet (P_STATE) to the peer.
If it decides to drbd_send_state(), it would however always send the
_curent_ state, which, if a second state change happens before the
after_state_ch() of the first ran, may "fast-forward" the peer's view
about this node.  In most cases that is harmless, but sometimes this can
confuse DRBD, for example into not actually starting a necessary resync
if you do a very tight detach/attach loop on a Connected Secondary.

Fix this by always sending the "new" state of the respective state
transition which scheduled this after_state_ch() work.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
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Lars Ellenberg authored and Philipp Reisner committed May 9, 2012
1 parent a2e9138 commit f479ea0
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Showing 4 changed files with 47 additions and 16 deletions.
4 changes: 2 additions & 2 deletions drivers/block/drbd/drbd_int.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1229,8 +1229,8 @@ extern int drbd_send_uuids(struct drbd_conf *mdev);
extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
extern int drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev);
extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags);
extern int _drbd_send_state(struct drbd_conf *mdev);
extern int drbd_send_state(struct drbd_conf *mdev);
extern int drbd_send_state(struct drbd_conf *mdev, union drbd_state s);
extern int drbd_send_current_state(struct drbd_conf *mdev);
extern int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
enum drbd_packets cmd, struct p_header80 *h,
size_t size, unsigned msg_flags);
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53 changes: 42 additions & 11 deletions drivers/block/drbd/drbd_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1487,7 +1487,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
/* Do not change the order of the if above and the two below... */
if (os.pdsk == D_DISKLESS && ns.pdsk > D_DISKLESS) { /* attach on the peer */
drbd_send_uuids(mdev);
drbd_send_state(mdev);
drbd_send_state(mdev, ns);
}
/* No point in queuing send_bitmap if we don't have a connection
* anymore, so check also the _current_ state, not only the new state
Expand Down Expand Up @@ -1552,14 +1552,14 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
drbd_send_sizes(mdev, 0, 0); /* to start sync... */
drbd_send_uuids(mdev);
drbd_send_state(mdev);
drbd_send_state(mdev, ns);
}

/* We want to pause/continue resync, tell peer. */
if (ns.conn >= C_CONNECTED &&
((os.aftr_isp != ns.aftr_isp) ||
(os.user_isp != ns.user_isp)))
drbd_send_state(mdev);
drbd_send_state(mdev, ns);

/* In case one of the isp bits got set, suspend other devices. */
if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
Expand All @@ -1569,10 +1569,10 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
/* Make sure the peer gets informed about eventual state
changes (ISP bits) while we were in WFReportParams. */
if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
drbd_send_state(mdev);
drbd_send_state(mdev, ns);

if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
drbd_send_state(mdev);
drbd_send_state(mdev, ns);

/* We are in the progress to start a full sync... */
if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
Expand Down Expand Up @@ -1612,7 +1612,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
"ASSERT FAILED: disk is %s during detach\n",
drbd_disk_str(mdev->state.disk));

if (drbd_send_state(mdev))
if (drbd_send_state(mdev, ns))
dev_info(DEV, "Notified peer that I am detaching my disk\n");

drbd_rs_cancel_all(mdev);
Expand Down Expand Up @@ -1642,7 +1642,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
mdev->rs_failed = 0;
atomic_set(&mdev->rs_pending_cnt, 0);

if (drbd_send_state(mdev))
if (drbd_send_state(mdev, ns))
dev_info(DEV, "Notified peer that I'm now diskless.\n");
/* corresponding get_ldev in __drbd_set_state
* this may finally trigger drbd_ldev_destroy. */
Expand All @@ -1651,7 +1651,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,

/* Notify peer that I had a local IO error, and did not detached.. */
if (os.disk == D_UP_TO_DATE && ns.disk == D_INCONSISTENT)
drbd_send_state(mdev);
drbd_send_state(mdev, ns);

/* Disks got bigger while they were detached */
if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
Expand All @@ -1669,7 +1669,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
/* sync target done with resync. Explicitly notify peer, even though
* it should (at least for non-empty resyncs) already know itself. */
if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
drbd_send_state(mdev);
drbd_send_state(mdev, ns);

/* This triggers bitmap writeout of potentially still unwritten pages
* if the resync finished cleanly, or aborted because of peer disk
Expand Down Expand Up @@ -2191,10 +2191,10 @@ int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags fl
}

/**
* drbd_send_state() - Sends the drbd state to the peer
* drbd_send_current_state() - Sends the drbd state to the peer
* @mdev: DRBD device.
*/
int drbd_send_state(struct drbd_conf *mdev)
int drbd_send_current_state(struct drbd_conf *mdev)
{
struct socket *sock;
struct p_state p;
Expand All @@ -2220,6 +2220,37 @@ int drbd_send_state(struct drbd_conf *mdev)
return ok;
}

/**
* drbd_send_state() - After a state change, sends the new state to the peer
* @mdev: DRBD device.
* @state: the state to send, not necessarily the current state.
*
* Each state change queues an "after_state_ch" work, which will eventually
* send the resulting new state to the peer. If more state changes happen
* between queuing and processing of the after_state_ch work, we still
* want to send each intermediary state in the order it occurred.
*/
int drbd_send_state(struct drbd_conf *mdev, union drbd_state state)
{
struct socket *sock;
struct p_state p;
int ok = 0;

mutex_lock(&mdev->data.mutex);

p.state = cpu_to_be32(state.i);
sock = mdev->data.socket;

if (likely(sock != NULL)) {
ok = _drbd_send_cmd(mdev, sock, P_STATE,
(struct p_header80 *)&p, sizeof(p), 0);
}

mutex_unlock(&mdev->data.mutex);

return ok;
}

int drbd_send_state_req(struct drbd_conf *mdev,
union drbd_state mask, union drbd_state val)
{
Expand Down
2 changes: 1 addition & 1 deletion drivers/block/drbd/drbd_nl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -432,7 +432,7 @@ drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
/* if this was forced, we should consider sync */
if (forced)
drbd_send_uuids(mdev);
drbd_send_state(mdev);
drbd_send_current_state(mdev);
}

drbd_md_sync(mdev);
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4 changes: 2 additions & 2 deletions drivers/block/drbd/drbd_receiver.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -899,7 +899,7 @@ static int drbd_connect(struct drbd_conf *mdev)
drbd_send_sync_param(mdev, &mdev->sync_conf);
drbd_send_sizes(mdev, 0, 0);
drbd_send_uuids(mdev);
drbd_send_state(mdev);
drbd_send_current_state(mdev);
clear_bit(USE_DEGR_WFC_T, &mdev->flags);
clear_bit(RESIZE_PENDING, &mdev->flags);

Expand Down Expand Up @@ -3294,7 +3294,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
/* Nowadays only used when forcing a node into primary role and
setting its disk to UpToDate with that */
drbd_send_uuids(mdev);
drbd_send_state(mdev);
drbd_send_current_state(mdev);
}
}

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