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From: Bart Van Assche <bvanassche@acm.org>
To: Jack Wang <jinpu.wang@cloud.ionos.com>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org
Cc: axboe@kernel.dk, hch@infradead.org, sagi@grimberg.me,
	leon@kernel.org, dledford@redhat.com, jgg@ziepe.ca,
	danil.kipnis@cloud.ionos.com, rpenyaev@suse.de,
	pankaj.gupta@cloud.ionos.com
Subject: Re: [PATCH v11 18/26] block/rnbd: client: main functionality
Date: Fri, 27 Mar 2020 21:45:55 -0700	[thread overview]
Message-ID: <198cd2da-cbf8-17b0-3ee5-5dec366a43e2@acm.org> (raw)
In-Reply-To: <20200320121657.1165-19-jinpu.wang@cloud.ionos.com>

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.

  reply	other threads:[~2020-03-28  4:46 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-20 12:16 [PATCH v11 00/26] RTRS (former IBTRS) RDMA Transport Library and RNBD (former IBNBD) RDMA Network Block Device Jack Wang
2020-03-20 12:16 ` [PATCH v11 01/26] sysfs: export sysfs_remove_file_self() Jack Wang
2020-03-20 12:16 ` [PATCH v11 02/26] RDMA/rtrs: public interface header to establish RDMA connections Jack Wang
2020-03-20 12:16 ` [PATCH v11 03/26] RDMA/rtrs: private headers with rtrs protocol structs and helpers Jack Wang
2020-03-20 12:16 ` [PATCH v11 04/26] RDMA/rtrs: core: lib functions shared between client and server modules Jack Wang
2020-03-28  4:26   ` Bart Van Assche
2020-03-30 10:34     ` Jinpu Wang
2020-03-30 22:25       ` Bart Van Assche
2020-03-31  7:11         ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 05/26] RDMA/rtrs: client: private header with client structs and functions Jack Wang
2020-03-20 12:16 ` [PATCH v11 06/26] RDMA/rtrs: client: main functionality Jack Wang
2020-03-20 12:16 ` [PATCH v11 07/26] RDMA/rtrs: client: statistics functions Jack Wang
2020-03-20 12:16 ` [PATCH v11 08/26] RDMA/rtrs: client: sysfs interface functions Jack Wang
2020-03-30 22:28   ` Bart Van Assche
2020-03-31  7:20     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 09/26] RDMA/rtrs: server: private header with server structs and functions Jack Wang
2020-03-20 12:16 ` [PATCH v11 10/26] RDMA/rtrs: server: main functionality Jack Wang
2020-03-20 12:16 ` [PATCH v11 11/26] RDMA/rtrs: server: statistics functions Jack Wang
2020-03-20 12:16 ` [PATCH v11 12/26] RDMA/rtrs: server: sysfs interface functions Jack Wang
2020-03-30 22:29   ` Bart Van Assche
2020-03-31  7:13     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 13/26] RDMA/rtrs: include client and server modules into kernel compilation Jack Wang
2020-03-20 12:16 ` [PATCH v11 14/26] RDMA/rtrs: a bit of documentation Jack Wang
2020-03-20 12:16 ` [PATCH v11 15/26] block: reexport bio_map_kern Jack Wang
2020-03-28  3:58   ` Bart Van Assche
2020-03-28  8:29     ` Christoph Hellwig
2020-03-28 16:16       ` Bart Van Assche
2020-03-29 15:05         ` Christoph Hellwig
2020-03-29 18:08           ` Chaitanya Kulkarni
2020-03-30  6:28             ` hch
2020-03-30 10:44           ` Jinpu Wang
2020-03-30 18:57             ` Chaitanya Kulkarni
2020-03-20 12:16 ` [PATCH v11 16/26] block/rnbd: private headers with rnbd protocol structs and helpers Jack Wang
2020-03-28  4:58   ` Bart Van Assche
2020-03-31  7:32     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 17/26] block/rnbd: client: private header with client structs and functions Jack Wang
2020-03-28  4:26   ` Bart Van Assche
2020-03-31  9:08     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 18/26] block/rnbd: client: main functionality Jack Wang
2020-03-28  4:45   ` Bart Van Assche [this message]
2020-03-31  9:23     ` Jinpu Wang
2020-04-02 16:27       ` Jinpu Wang
2020-03-28  4:59   ` Bart Van Assche
2020-03-31  9:25     ` Jinpu Wang
2020-03-31 14:12       ` Bart Van Assche
2020-03-31 14:20         ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 19/26] block/rnbd: client: sysfs interface functions Jack Wang
2020-03-28  4:59   ` Bart Van Assche
2020-03-31  9:26     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 20/26] block/rnbd: server: private header with server structs and functions Jack Wang
2020-03-20 12:16 ` [PATCH v11 21/26] block/rnbd: server: main functionality Jack Wang
2020-03-28 17:40   ` Bart Van Assche
2020-03-31  9:29     ` Jinpu Wang
2020-03-31 15:32       ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 22/26] block/rnbd: server: functionality for IO submission to file or block dev Jack Wang
2020-03-28 18:39   ` Bart Van Assche
2020-03-31 10:06     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 23/26] block/rnbd: server: sysfs interface functions Jack Wang
2020-03-28 19:31   ` Bart Van Assche
2020-03-28 23:06     ` Jason Gunthorpe
2020-03-30 13:14     ` Danil Kipnis
2020-03-20 12:16 ` [PATCH v11 24/26] block/rnbd: include client and server modules into kernel compilation Jack Wang
2020-03-28 19:34   ` Bart Van Assche
2020-03-31  7:23     ` Jinpu Wang
2020-03-20 12:16 ` [PATCH v11 25/26] block/rnbd: a bit of documentation Jack Wang
2020-03-28 19:40   ` Bart Van Assche
2020-03-30 10:17     ` Danil Kipnis
2020-03-20 12:16 ` [PATCH v11 26/26] MAINTAINERS: Add maintainers for RNBD/RTRS modules Jack Wang
2020-03-28 19:40   ` Bart Van Assche
2020-03-30 10:12     ` Danil Kipnis
2020-03-26 17:38 ` [PATCH v11 00/26] RTRS (former IBTRS) RDMA Transport Library and RNBD (former IBNBD) RDMA Network Block Device Jinpu Wang

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