drbd: Create new current UUID as late as possible

The choice was to either delay creation of the new UUID until
IO got thawed or to delay it until the first IO request.

Both are correct, the later is more friendly to users of
dual-primary setups, that actually only write on one side.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 20 insertions, 5 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index d0fabac..c144509 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1217,17 +1217,16 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 		mdev->p_uuid = NULL;
 		if (get_ldev(mdev)) {
 			if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
-			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
-				drbd_uuid_new_current(mdev);
-				drbd_send_uuids(mdev);
-			}
+			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE)
+				atomic_set(&mdev->new_c_uuid, 2);
 			put_ldev(mdev);
 		}
 	}
 
 	if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
+		/* Diskless peer becomes primary or got connected do diskless, primary peer. */
 		if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0)
-			drbd_uuid_new_current(mdev);
+			atomic_set(&mdev->new_c_uuid, 2);
 
 		/* D_DISKLESS Peer becomes secondary */
 		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
@@ -1351,6 +1350,19 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	drbd_md_sync(mdev);
 }
 
+static int w_new_current_uuid(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	if (get_ldev(mdev)) {
+		drbd_uuid_new_current(mdev);
+		drbd_send_uuids(mdev);
+		drbd_md_sync(mdev);
+		put_ldev(mdev);
+	}
+	atomic_dec(&mdev->new_c_uuid);
+	wake_up(&mdev->misc_wait);
+
+	return 1;
+}
 
 static int drbd_thread_setup(void *arg)
 {
@@ -2691,6 +2703,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	atomic_set(&mdev->net_cnt, 0);
 	atomic_set(&mdev->packet_seq, 0);
 	atomic_set(&mdev->pp_in_use, 0);
+	atomic_set(&mdev->new_c_uuid, 0);
 
 	mutex_init(&mdev->md_io_mutex);
 	mutex_init(&mdev->data.mutex);
@@ -2721,12 +2734,14 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
 	INIT_LIST_HEAD(&mdev->delay_probes);
 	INIT_LIST_HEAD(&mdev->delay_probe_work.list);
+	INIT_LIST_HEAD(&mdev->uuid_work.list);
 
 	mdev->resync_work.cb  = w_resync_inactive;
 	mdev->unplug_work.cb  = w_send_write_hint;
 	mdev->md_sync_work.cb = w_md_sync;
 	mdev->bm_io_work.w.cb = w_bitmap_io;
 	mdev->delay_probe_work.cb = w_delay_probes;
+	mdev->uuid_work.cb = w_new_current_uuid;
 	init_timer(&mdev->resync_timer);
 	init_timer(&mdev->md_sync_timer);
 	init_timer(&mdev->delay_probe_timer);