drbd: Removed a race that could cause unexpected execution of w_make_resync_request()

The actual race happened int the drbd_start_resync() function. Where
drbd_resync_finished() -> __drbd_set_state() set STOP_SYNC_TIMER and
armed the timer.

If the timer fired before execution reaches the mod_timer statement
at the end of drbd_start_resync() the latter would cause an
unexpected call to w_make_resync_request().

Removed the STOP_SYNC_TIMER bit, and base it on the connection state.

The STOP_SYNC_TIMER bit probably originates probably the time before
the state engine.

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

1 files changed, 9 insertions, 12 deletions

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 8be983263374..0e5bf8c98293 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -395,25 +395,22 @@ defer:
 
 void resync_timer_fn(unsigned long data)
 {
-	unsigned long flags;
 	struct drbd_conf *mdev = (struct drbd_conf *) data;
 	int queue;
 
-	spin_lock_irqsave(&mdev->req_lock, flags);
-
-	if (likely(!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))) {
-		queue = 1;
-		if (mdev->state.conn == C_VERIFY_S)
-			mdev->resync_work.cb = w_make_ov_request;
-		else
-			mdev->resync_work.cb = w_make_resync_request;
-	} else {
+	queue = 1;
+	switch (mdev->state.conn) {
+	case C_VERIFY_S:
+		mdev->resync_work.cb = w_make_ov_request;
+		break;
+	case C_SYNC_TARGET:
+		mdev->resync_work.cb = w_make_resync_request;
+		break;
+	default:
 		queue = 0;
 		mdev->resync_work.cb = w_resync_inactive;
 	}
 
-	spin_unlock_irqrestore(&mdev->req_lock, flags);
-
 	/* harmless race: list_empty outside data.work.q_lock */
 	if (list_empty(&mdev->resync_work.list) && queue)
 		drbd_queue_work(&mdev->data.work, &mdev->resync_work);