After flush plug list, the list has no request, so we need to add a
trace_block_plug().
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Reviewed-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>