On 2020-03-20 05:16, Jack Wang wrote:
> +static void rnbd_clt_put_dev(struct rnbd_clt_dev *dev)
> +{
> + might_sleep();
> +
> + if (refcount_dec_and_test(&dev->refcount)) {
> + mutex_lock(&ida_lock);
> + ida_simple_remove(&index_ida, dev->clt_device_id);
> + mutex_unlock(&ida_lock);
> + kfree(dev->hw_queues);
> + rnbd_clt_put_sess(dev->sess);
> + mutex_destroy(&dev->lock);
> + kfree(dev);
> + }
> +}
Please use the coding style that is used elsewhere in the kernel, namely
return early to keep the indentation level low.
> +enum {
> + RNBD_DELAY_10ms = 10,
> + RNBD_DELAY_IFBUSY = -1,
> +};
How about removing the RNBD_DELAY_10ms constant and using 10/*ms*/ instead?
> +enum {
> + NO_WAIT = 0,
> + WAIT = 1
> +};
> +
> +static int send_usr_msg(struct rtrs_clt *rtrs, int dir,
> + struct rnbd_iu *iu, struct kvec *vec, size_t nr,
> + size_t len, struct scatterlist *sg, unsigned int sg_len,
> + void (*conf)(struct work_struct *work),
> + int *errno, bool wait)
Are the NO_WAIT and WAIT perhaps values that are passed as the last
argument to send_usr_msg()? If so, please use a proper enumeration type
instead of 'bool'.
> +static int rnbd_client_getgeo(struct block_device *block_device,
> + struct hd_geometry *geo)
> +{
> + u64 size;
> + struct rnbd_clt_dev *dev;
> +
> + dev = block_device->bd_disk->private_data;
> + size = dev->size * (dev->logical_block_size / SECTOR_SIZE);
> + geo->cylinders = (size & ~0x3f) >> 6; /* size/64 */
> + geo->heads = 4;
> + geo->sectors = 16;
> + geo->start = 0;
> +
> + return 0;
> +}
Is the "& ~0x3f" in the above function perhaps superfluous?
> +static void rnbd_clt_dev_kick_mq_queue(struct rnbd_clt_dev *dev,
> + struct blk_mq_hw_ctx *hctx,
> + int delay)
> +{
> + struct rnbd_queue *q = hctx->driver_data;
> +
> + if (delay != RNBD_DELAY_IFBUSY)
> + blk_mq_delay_run_hw_queue(hctx, delay);
> + else if (unlikely(!rnbd_clt_dev_add_to_requeue(dev, q)))
> + /*
> + * If session is not busy we have to restart
> + * the queue ourselves.
> + */
> + blk_mq_delay_run_hw_queue(hctx, RNBD_DELAY_10ms);
> +}
I think the above code will be easier to read if RNBD_DELAY_10ms is
changed into 10/*ms*/.
> +static blk_status_t rnbd_queue_rq(struct blk_mq_hw_ctx *hctx,
> + const struct blk_mq_queue_data *bd)
> +{
> + struct request *rq = bd->rq;
> + struct rnbd_clt_dev *dev = rq->rq_disk->private_data;
> + struct rnbd_iu *iu = blk_mq_rq_to_pdu(rq);
> + int err;
> +
> + if (unlikely(dev->dev_state != DEV_STATE_MAPPED))
> + return BLK_STS_IOERR;
> +
> + iu->permit = rnbd_get_permit(dev->sess, RTRS_IO_CON,
> + RTRS_PERMIT_NOWAIT);
> + if (unlikely(!iu->permit)) {
> + rnbd_clt_dev_kick_mq_queue(dev, hctx, RNBD_DELAY_IFBUSY);
> + return BLK_STS_RESOURCE;
> + }
> +
> + blk_mq_start_request(rq);
> + err = rnbd_client_xfer_request(dev, rq, iu);
> + if (likely(err == 0))
> + return BLK_STS_OK;
> + if (unlikely(err == -EAGAIN || err == -ENOMEM)) {
> + rnbd_clt_dev_kick_mq_queue(dev, hctx, RNBD_DELAY_10ms);
> + rnbd_put_permit(dev->sess, iu->permit);
> + return BLK_STS_RESOURCE;
> + }
> +
> + rnbd_put_permit(dev->sess, iu->permit);
> + return BLK_STS_IOERR;
> +}
Would it be possible to use the .get_budget / .put_budget callbacks for
obtaining / releasing a "permit" object? I'm asking this because it was
really tricky to get the .get_budget / .put_budget calls right in the
block layer core. See also commit 0bca799b9280 ("blk-mq: order getting
budget and driver tag") # v4.17.
Thanks,
Bart.
