linux-kernel - Re: [PATCH RFC v3 04/22] scsi: core: Add support to send reserved commands

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Message-ID: <76fe5007-5c53-9cdf-7c57-6af7ebaf8c97@huawei.com>
Date:   Thu, 27 Oct 2022 10:13:24 +0100
From:   John Garry <john.garry@...wei.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        <axboe@...nel.dk>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <jinpu.wang@...ud.ionos.com>,
        <hare@...e.de>, <bvanassche@....org>, <hch@....de>,
        <ming.lei@...hat.com>, <niklas.cassel@....com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-ide@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <linuxarm@...wei.com>
Subject: Re: [PATCH RFC v3 04/22] scsi: core: Add support to send reserved
 commands

On 27/10/2022 02:21, Damien Le Moal wrote:
>>   
>> +	if (blk_mq_is_reserved_rq(rq)) {
>> +		struct scsi_device *sdev = cmd->device;
> This variable is not really needed. You can call:
> 		
> 		scsi_device_unbusy(cmd->device, cmd);
> 
> No ?

ok, your suggestion is good

> 
>> +
>> +		scsi_mq_uninit_cmd(cmd);
>> +		scsi_device_unbusy(sdev, cmd);
>> +		__blk_mq_end_request(rq, 0);
>> +
>> +		return;
>> +	}
>> +
>>   	INIT_LIST_HEAD(&cmd->eh_entry);
>>   
>>   	atomic_inc(&cmd->device->iodone_cnt);
>> @@ -1718,6 +1728,21 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
>>   	blk_status_t ret;
>>   	int reason;
>>   
>> +	if (blk_mq_is_reserved_rq(req)) {
>> +		if (!(req->rq_flags & RQF_DONTPREP)) {
>> +			ret = scsi_prepare_cmd(req);
>> +			if (ret != BLK_STS_OK)
>> +				goto out_dec_host_busy;
>> +
>> +			req->rq_flags |= RQF_DONTPREP;
>> +		} else {
>> +			clear_bit(SCMD_STATE_COMPLETE, &cmd->state);
>> +		}
>> +		blk_mq_start_request(req);
>> +
>> +		return shost->hostt->reserved_queuecommand(shost, cmd);
>> +	}
>> +
>>   	WARN_ON_ONCE(cmd->budget_token < 0);
>>   
>>   	/*
>> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
>> index 91678c77398e..a39f36aa0b0d 100644
>> --- a/include/scsi/scsi_host.h
>> +++ b/include/scsi/scsi_host.h
>> @@ -73,6 +73,7 @@ struct scsi_host_template {
>>   	 * STATUS: REQUIRED
>>   	 */
>>   	int (* queuecommand)(struct Scsi_Host *, struct scsi_cmnd *);
>> +	int (*reserved_queuecommand)(struct Scsi_Host *, struct scsi_cmnd *);
> Nit: This op name sound like something returning a bool... May be a
> straight "queue_reserved_command" name would be clearer ?

or queuecommand_reserved ? I'm just trying to have the name a variant of 
"queuecommand".

> 

thanks,
John