linux-kernel - Re: [RFC PATCH 4/5] scsi: ufs: L2P map management for HPB read

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Message-ID: <6d570594-96f8-764e-e252-97a714731650@acm.org>
Date:   Sat, 13 Jun 2020 08:24:04 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     daejun7.park@...sung.com, ALIM AKHTAR <alim.akhtar@...sung.com>,
        "avri.altman@....com" <avri.altman@....com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@...sung.com>,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        Adel Choi <adel.choi@...sung.com>,
        BoRam Shin <boram.shin@...sung.com>
Subject: Re: [RFC PATCH 4/5] scsi: ufs: L2P map management for HPB read

On 2020-06-11 20:37, Daejun Park wrote:
>>> +static int ufshpb_execute_map_req(struct ufshpb_lu *hpb,
>>> +				  struct ufshpb_req *map_req)
>>> +{
>>> +	struct request_queue *q;
>>> +	struct request *req;
>>> +	struct scsi_request *rq;
>>> +	int ret = 0;
>>> +
>>> +	q = hpb->sdev_ufs_lu->request_queue;
>>> +	ret = ufshpb_map_req_add_bio_page(hpb, q, map_req->bio,
>>> +					  map_req->mctx);
>>> +	if (ret) {
>>> +		dev_notice(&hpb->hpb_lu_dev,
>>> +			   "map_req_add_bio_page fail %d - %d\n",
>>> +			   map_req->rgn_idx, map_req->srgn_idx);
>>> +		return ret;
>>> +	}
>>> +
>>> +	req = map_req->req;
>>> +
>>> +	blk_rq_append_bio(req, &map_req->bio);
>>> +	req->rq_flags |= RQF_QUIET;
>>> +	req->timeout = MAP_REQ_TIMEOUT;
>>> +	req->end_io_data = (void *)map_req;
>>> +
>>> +	rq = scsi_req(req);
>>> +	ufshpb_set_read_buf_cmd(rq->cmd, map_req->rgn_idx,
>>> +				map_req->srgn_idx, hpb->srgn_mem_size);
>>> +	rq->cmd_len = HPB_READ_BUFFER_CMD_LENGTH;
>>> +
>>> +	blk_execute_rq_nowait(q, NULL, req, 1, ufshpb_map_req_compl_fn);
>>> +
>>> +	atomic_inc(&hpb->stats.map_req_cnt);
>>> +	return 0;
>>> +}
>> 
>> Why a custom timeout instead of the SCSI LUN timeout?
>
> There was no suitable timeout value to use. I've included sd.h, so I'll
> use sd_timeout.

Wouldn't that be a layering violation? The UFS driver is a SCSI LLD
driver and the sd driver is a SCSI ULD. A SCSI LLD must not make any
assumptions about which ULD driver has been attached.

How about leaving req->timeout zero such that blk_add_timer() sets it?
blk_add_timer() is called by blk_mq_start_request(). From blk_add_timer():

	if (!req->timeout)
		req->timeout = q->rq_timeout;

Thanks,

Bart.