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drbd: fix race between role change and handshake

Browse Source 
Symptoms:
If DRBD was "cleanly shut down" (all in sync, both Secondary before
disconnect, identical data generation uuids), and then one side was
promoted *during* the next connection handshake, the role change
could confuse the handshake.

The Primary would get stuck in WFBitmapS, the Secondary would log
unexpected cstate (Connected) in receive_bitmap
and get stuck in WFBitmapT.

Fix:
The test in is_valid_soft_transition wrong. It works because
the not allowed actions (promote/attach) do not touch the
cstate. The previous condition failed to demand a cstate change
in one clause.

In order to avoid deadlocks give up the state_mutex while waiting
for the transient state to go away.

Conflicts:
	drbd/drbd_state.c
	drbd/drbd_state.h
	drbd/drbd_wrappers.h

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Philipp Reisner 2014-11-10 17:21:11 +01:00 committed by Jens Axboe
parent f221f4bcc5
commit a88215312c
3 changed files with 40 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/block/drbd/drbd_nl.c
View File

@ -588,7 +588,7 @@ drbd_set_role(struct drbd_device *const device, enum drbd_role new_role, int for
val.i = 0; val.role = new_role;
while (try++ < max_tries) {
rv = _drbd_request_state(device, mask, val, CS_WAIT_COMPLETE);
rv = _drbd_request_state_holding_state_mutex(device, mask, val, CS_WAIT_COMPLETE);
/* in case we first succeeded to outdate,
* but now suddenly could establish a connection */

41
drivers/block/drbd/drbd_state.c
View File

@ -215,6 +215,18 @@ static bool no_peer_wf_report_params(struct drbd_connection *connection)
return rv;
}
static void wake_up_all_devices(struct drbd_connection *connection)
{
struct drbd_peer_device *peer_device;
int vnr;
rcu_read_lock();
idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
wake_up(&peer_device->device->state_wait);
rcu_read_unlock();
}
/**
* cl_wide_st_chg() - true if the state change is a cluster wide one
@ -410,6 +422,22 @@ _drbd_request_state(struct drbd_device *device, union drbd_state mask,
return rv;
}
enum drbd_state_rv
_drbd_request_state_holding_state_mutex(struct drbd_device *device, union drbd_state mask,
union drbd_state val, enum chg_state_flags f)
{
enum drbd_state_rv rv;
BUG_ON(f & CS_SERIALIZE);
wait_event_cmd(device->state_wait,
(rv = drbd_req_state(device, mask, val, f)) != SS_IN_TRANSIENT_STATE,
mutex_unlock(device->state_mutex),
mutex_lock(device->state_mutex));
return rv;
}
static void print_st(struct drbd_device *device, const char *name, union drbd_state ns)
{
drbd_err(device, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c%c%c }\n",
@ -629,14 +657,11 @@ is_valid_soft_transition(union drbd_state os, union drbd_state ns, struct drbd_c
if (ns.conn == C_DISCONNECTING && os.conn == C_UNCONNECTED)
rv = SS_IN_TRANSIENT_STATE;
/* if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
rv = SS_IN_TRANSIENT_STATE; */
/* While establishing a connection only allow cstate to change.
Delay/refuse role changes, detach attach etc... */
Delay/refuse role changes, detach attach etc... (they do not touch cstate) */
if (test_bit(STATE_SENT, &connection->flags) &&
!(os.conn == C_WF_REPORT_PARAMS ||
(ns.conn == C_WF_REPORT_PARAMS && os.conn == C_WF_CONNECTION)))
!((ns.conn == C_WF_REPORT_PARAMS && os.conn == C_WF_CONNECTION) ||
(ns.conn >= C_CONNECTED && os.conn == C_WF_REPORT_PARAMS)))
rv = SS_IN_TRANSIENT_STATE;
if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
@ -1032,8 +1057,10 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
/* Wake up role changes, that were delayed because of connection establishing */
if (os.conn == C_WF_REPORT_PARAMS && ns.conn != C_WF_REPORT_PARAMS &&
no_peer_wf_report_params(connection))
no_peer_wf_report_params(connection)) {
clear_bit(STATE_SENT, &connection->flags);
wake_up_all_devices(connection);
}
wake_up(&device->misc_wait);
wake_up(&device->state_wait);

5
drivers/block/drbd/drbd_state.h
View File

@ -117,6 +117,11 @@ extern enum drbd_state_rv _drbd_request_state(struct drbd_device *,
union drbd_state,
union drbd_state,
enum chg_state_flags);
extern enum drbd_state_rv
_drbd_request_state_holding_state_mutex(struct drbd_device *, union drbd_state,
union drbd_state, enum chg_state_flags);
extern enum drbd_state_rv __drbd_set_state(struct drbd_device *, union drbd_state,
enum chg_state_flags,
struct completion *done);