Ceph » rbd

AbstractWriteLog::m_lock vs ImageCtx::owner_lock lock ordering

AbstractWriteLog::periodic_stats() takes m_lock and ends up calling AbstractWriteLog::write_image_cache_state():

periodic_stats
  update_image_cache_state
    update_image_cache_state(Context*)
      write_image_cache_state

write_image_cache_state() takes owner_lock, so we have m_lock -> owner_lock order.

SnapshotCreateRequest::handle_notify_quiesce() takes owner_lock and ends up executing GuardedRequestFunctionContext callback:

handle_notify_quiesce
  send_suspend_requests
    send_suspend_aio
      WriteBlockImageDispatch::block_writes
        WriteBlockImageDispatch::flush_io
          ImageDispatchSpec::send
            ...
              WriteLogImageDispatch::flush
                AbstractWriteLog::flush
                  internal_flush
                    detain_guarded_request
                      Context::complete
                        GuardedRequestFunctionContext::finish

The callback may take m_lock, e.g. one defined in AbstractWriteLog::flush() or in AbstractWriteLog::internal_flush(), so we have owner_lock -> m_lock order.