[PATCH v2] nvmet: avoid unnecessary fsync and flush bio

[Christoph Hellwig]

On Mon, Jul 25, 2022 at 02:28:18PM +0800, Guixin Liu wrote:
>  u16 nvmet_file_flush(struct nvmet_req *req)
>  {
> -	return errno_to_nvme_status(req, vfs_fsync(req->ns->file, 1));
> +	if (req->ns->buffered_io)
> +		return errno_to_nvme_status(req, vfs_fsync(req->ns->file, 1));
> +	return NVME_SC_SUCCESS;

This is broken.  Even direct I/O needs an fsync to commit metadata
changes.