Re: [PATCH] nbd: fix partial sending

[Bart Van Assche <bvanassche@acm.org>]

On 10/17/24 4:36 AM, Ming Lei wrote:
> +static blk_status_t nbd_send_pending_cmd(struct nbd_device *nbd,
> +		struct nbd_cmd *cmd)
> +{
> +	struct request *req = blk_mq_rq_from_pdu(cmd);
> +	unsigned long deadline = READ_ONCE(req->deadline);
> +	unsigned int wait_ms = 2;
> +	blk_status_t res;
> +
> +	WARN_ON_ONCE(test_bit(NBD_CMD_REQUEUED, &cmd->flags));
> +
> +	while (true) {
> +		res = nbd_send_cmd(nbd, cmd, cmd->index);
> +		if (res != BLK_STS_RESOURCE)
> +			return res;
> +		if (READ_ONCE(jiffies) + msecs_to_jiffies(wait_ms) >= deadline)
> +			break;
> +		msleep(wait_ms);
> +		wait_ms *= 2;
> +	}

I think that there are better solutions to wait until more data
can be sent, e.g. by using the kernel equivalent of the C library
function select().

Thanks,

Bart.