librbd: track in-flight flush events for journaling

The tracking for flush events was accidentally dropped. This
can result in the journal being closed too early since it
might miss in-flight flush ops.

Signed-off-by: Jason Dillaman <dillaman@redhat.com>

src/librbd/AioCompletion.cc

@@ -135,11 +135,11 @@ namespace librbd {
     }
   }
 
-  void AioCompletion::start_op() {
+  void AioCompletion::start_op(bool ignore_type) {
     Mutex::Locker locker(lock);
     assert(ictx != nullptr);
     assert(!async_op.started());
-    if (state == STATE_PENDING && aio_type != AIO_TYPE_FLUSH) {
+    if (state == STATE_PENDING && (ignore_type || aio_type != AIO_TYPE_FLUSH)) {
       async_op.start_op(*ictx);
     }
   }

src/librbd/AioCompletion.h

@@ -118,7 +118,7 @@ namespace librbd {
     void finalize(ssize_t rval);
 
     void init_time(ImageCtx *i, aio_type_t t);
-    void start_op();
+    void start_op(bool ignore_type = false);
     void fail(int r);
 
     void complete();

src/librbd/AioImageRequest.cc

@@ -472,6 +472,8 @@ void AioImageFlush::send_request() {
   C_AioRequest *req_comp = new C_AioRequest(m_aio_comp);
   m_image_ctx.flush(req_comp);
 
+  // track flush op for block writes
+  m_aio_comp->start_op(true);
   m_aio_comp->put();
 
   m_image_ctx.perfcounter->inc(l_librbd_aio_flush);