[PATCH 15/30] drbd: finish resync on sync source only by notification from sync target

From: Philipp Reisner
Date: Mon Jun 13 2016 - 18:31:41 EST


From: Lars Ellenberg <lars@xxxxxxxxxx>

If the replication link breaks exactly during "resync finished" detection,
finishing too early on the sync source could again lead to UUIDs rotated
too fast, and potentially a spurious full resync on next handshake.

Always wait for explicit resync finished state change notification from
the sync target.

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_actlog.c | 16 ++++++++++++----
drivers/block/drbd/drbd_int.h | 19 ++++++++++++++-----
2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 265b2b6..cafa9c4 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -770,10 +770,18 @@ static bool lazy_bitmap_update_due(struct drbd_device *device)

static void maybe_schedule_on_disk_bitmap_update(struct drbd_device *device, bool rs_done)
{
- if (rs_done)
- set_bit(RS_DONE, &device->flags);
- /* and also set RS_PROGRESS below */
- else if (!lazy_bitmap_update_due(device))
+ if (rs_done) {
+ struct drbd_connection *connection = first_peer_device(device)->connection;
+ if (connection->agreed_pro_version <= 95 ||
+ is_sync_target_state(device->state.conn))
+ set_bit(RS_DONE, &device->flags);
+ /* and also set RS_PROGRESS below */
+
+ /* Else: rather wait for explicit notification via receive_state,
+ * to avoid uuids-rotated-too-fast causing full resync
+ * in next handshake, in case the replication link breaks
+ * at the most unfortunate time... */
+ } else if (!lazy_bitmap_update_due(device))
return;

drbd_device_post_work(device, RS_PROGRESS);
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 9c68ec5..c5dbc85 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2102,13 +2102,22 @@ static inline void _sub_unacked(struct drbd_device *device, int n, const char *f
ERR_IF_CNT_IS_NEGATIVE(unacked_cnt, func, line);
}

+static inline bool is_sync_target_state(enum drbd_conns connection_state)
+{
+ return connection_state == C_SYNC_TARGET ||
+ connection_state == C_PAUSED_SYNC_T;
+}
+
+static inline bool is_sync_source_state(enum drbd_conns connection_state)
+{
+ return connection_state == C_SYNC_SOURCE ||
+ connection_state == C_PAUSED_SYNC_S;
+}
+
static inline bool is_sync_state(enum drbd_conns connection_state)
{
- return
- (connection_state == C_SYNC_SOURCE
- || connection_state == C_SYNC_TARGET
- || connection_state == C_PAUSED_SYNC_S
- || connection_state == C_PAUSED_SYNC_T);
+ return is_sync_source_state(connection_state) ||
+ is_sync_target_state(connection_state);
}

/**
--
2.7.4