Use sync_blockdev instead of opencoding it. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> Link: https://lore.kernel.org/r/20211019062530.2174626-4-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>