Re: [PATCH v2 5/5] scsi: ufs: UFS Host Performance Booster(HPB) driver

[Bean Huo]

On 25.04.20 20:07, Bart Van Assche wrote:
> On 2020-04-16 13:31, huobean@xxxxxxxxx wrote:
> > +static int ufshpb_execute_cmd(struct ufshpb_lu *hpb, unsigned char *cmd)
> > +{
> > +	struct scsi_sense_hdr sshdr;
> > +	struct scsi_device *sdp;
> > +	struct ufs_hba *hba;
> > +	int retries;
> > +	int ret = 0;
> > +
> > +	hba = hpb->hba;
> > +
> > +	sdp = hba->sdev_ufs_lu[hpb->lun];
> > +	if (!sdp) {
> > +		hpb_warn("%s UFSHPB cannot find scsi_device\n",  __func__);
> > +		return -ENODEV;
> > +	}
> > +
> > +	ret = scsi_device_get(sdp);
> > +	if (!ret && !scsi_device_online(sdp)) {
> > +		ret = -ENODEV;
> > +		scsi_device_put(sdp);
> > +		return ret;
> > +	}
> > +
> > +	for (retries = 3; retries > 0; --retries) {
> > +		ret = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL, &sshdr,
> > +				   msecs_to_jiffies(30000), 3, 0, RQF_PM, NULL);
> > +		if (ret == 0)
> > +			break;
> > +	}
> > +
> > +	if (ret) {
> > +		if (driver_byte(ret) == DRIVER_SENSE &&
> > +		    scsi_sense_valid(&sshdr)) {
> > +			switch (sshdr.sense_key) {
> > +			case ILLEGAL_REQUEST:
> > +				hpb_err("ILLEGAL REQUEST asc=0x%x ascq=0x%x\n",
> > +					sshdr.asc, sshdr.ascq);
> > +				break;
> > +			default:
> > +				hpb_err("Unknown return code = %x\n", ret);
> > +				break;
> > +			}
> > +		}
> > +	}
> > +	scsi_device_put(sdp);
> > +
> > +	return ret;
> > +}
> If scsi_execute() would be changed into asynchronous SCSI command
> submission, can ufshpb_execute_cmd() be called from inside the UFS
> .queue_rq() callback instead of from workqueue context?
>
> The scsi_device_get() call looks misplaced. I think that call should
> happen before schedule_work() is called.
>
> > +static int ufshpb_l2p_load_req(struct ufshpb_lu *hpb, struct request_queue *q,
> > +			       struct ufshpb_map_req *map_req)
> > +{
> > +	struct scsi_request *scsi_rq;
> > +	unsigned char cmd[16] = { };
> > +	struct request *req;
> > +	struct bio *bio;
> > +	int alloc_len;
> > +	int ret;
> > +
> > +	bio = &map_req->bio;
> > +
> > +	ret = ufshpb_add_bio_page(hpb, q, bio, map_req->bvec, map_req->mctx);
> > +	if (ret) {
> > +		hpb_err("ufshpb_add_bio_page() failed with ret %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	alloc_len = hpb->hba->hpb_geo.subregion_entry_sz;
> > +	/*
> > +	 * HPB Sub-Regions are equally sized except for the last one which is
> > +	 * smaller if the last hpb Region is not an integer multiple of
> > +	 * bHPBSubRegionSize.
> > +	 */
> > +	if (map_req->region == (hpb->lu_region_cnt - 1) &&
> > +	    map_req->subregion == (hpb->subregions_in_last_region - 1))
> > +		alloc_len = hpb->last_subregion_entry_size;
> > +
> > +	ufshpb_prepare_read_buf_cmd(cmd, map_req->region, map_req->subregion,
> > +				    alloc_len);
> > +	if (!map_req->req) {
> > +		map_req->req = blk_get_request(q, REQ_OP_SCSI_IN, 0);
> > +		if (IS_ERR(map_req->req))
> > +			return PTR_ERR(map_req->req);
> > +	}
> > +	req = map_req->req;
> > +	scsi_rq = scsi_req(req);
> > +
> > +	blk_rq_append_bio(req, &bio);
> > +
> > +	scsi_req_init(scsi_rq);
> > +
> > +	scsi_rq->cmd_len = COMMAND_SIZE(cmd[0]);
> > +	memcpy(scsi_rq->cmd, cmd, scsi_rq->cmd_len);
> > +	req->timeout = msecs_to_jiffies(30000);
> > +	req->end_io_data = (void *)map_req;
> > +
> > +	hpb_dbg(SCHEDULE_INFO, hpb, "ISSUE READ_BUFFER : (%d-%d) retry = %d\n",
> > +		map_req->region, map_req->subregion, map_req->retry_cnt);
> > +	hpb_trace(hpb, "%s: I RB %d - %d", DRIVER_NAME, map_req->region,
> > +		  map_req->subregion);
> > +
> > +	blk_execute_rq_nowait(q, NULL, req, 1, ufshpb_l2p_load_req_done);
> > +	map_req->req_issue_t = ktime_to_ns(ktime_get());
> > +
> > +	atomic64_inc(&hpb->status.map_req_cnt);
> > +
> > +	return 0;
> > +}
> Same question here: if 'req' would be submitted asynchronously, can
> ufshpb_l2p_load_req() be called directly from inside the UFS .queue_rq()
> callback instead of from workqueue context?
>
> Thanks,
>
> Bart.

Hi, Bart
Thanks very much.
If I understood the Christoph's the second question correctly. Enqueue 
HPB requests to the
scsi_device->request_queueu, and fly back to SCSI schedule, it's 
unacceptable. I don't like this
implementation way either. Also, the latency of the L2P table update is 
higher. I will change it
in the RFC patch.

thanks,
Bean