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Subject: Re: [PATCH 2/4] null_blk: add zone open, close, and finish support
To:     Damien Le Moal <Damien.LeMoal@wdc.com>,
        "axboe@fb.com" <axboe@fb.com>, "hch@lst.de" <hch@lst.de>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        Dmitry Fomichev <Dmitry.Fomichev@wdc.com>,
        Ajay Joshi <Ajay.Joshi@wdc.com>,
        Aravind Ramesh <Aravind.Ramesh@wdc.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "James.Bottomley@HansenPartnership.com" 
        <James.Bottomley@HansenPartnership.com>,
        "agk@redhat.com" <agk@redhat.com>,
        "snitzer@redhat.com" <snitzer@redhat.com>
Cc:     "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "dm-devel@redhat.com" <dm-devel@redhat.com>,
        Matias Bjorling <Matias.Bjorling@wdc.com>
References: <20190621130711.21986-1-mb@lightnvm.io>
 <20190621130711.21986-3-mb@lightnvm.io>
 <BYAPR04MB5816D471063D970DDCF9AEC7E7E60@BYAPR04MB5816.namprd04.prod.outlook.com>
From:   =?UTF-8?Q?Matias_Bj=c3=b8rling?= <mb@lightnvm.io>
Message-ID: <1aa6552c-ecf9-a168-df75-ec8c52ddbea6@lightnvm.io>
Date:   Tue, 25 Jun 2019 13:06:33 +0200
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On 6/22/19 3:02 AM, Damien Le Moal wrote:
> On 2019/06/21 22:07, Matias Bjørling wrote:
>> From: Ajay Joshi <ajay.joshi@wdc.com>
>>
>> Implement REQ_OP_ZONE_OPEN, REQ_OP_ZONE_CLOSE and REQ_OP_ZONE_FINISH
>> support to allow explicit control of zone states.
>>
>> Signed-off-by: Ajay Joshi <ajay.joshi@wdc.com>
>> Signed-off-by: Matias Bjørling <matias.bjorling@wdc.com>
>> ---
>>   drivers/block/null_blk.h       |  4 ++--
>>   drivers/block/null_blk_main.c  | 13 ++++++++++---
>>   drivers/block/null_blk_zoned.c | 33 ++++++++++++++++++++++++++++++---
>>   3 files changed, 42 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/block/null_blk.h b/drivers/block/null_blk.h
>> index 34b22d6523ba..62ef65cb0f3e 100644
>> --- a/drivers/block/null_blk.h
>> +++ b/drivers/block/null_blk.h
>> @@ -93,7 +93,7 @@ int null_zone_report(struct gendisk *disk, sector_t sector,
>>   		     gfp_t gfp_mask);
>>   void null_zone_write(struct nullb_cmd *cmd, sector_t sector,
>>   			unsigned int nr_sectors);
>> -void null_zone_reset(struct nullb_cmd *cmd, sector_t sector);
>> +void null_zone_mgmt_op(struct nullb_cmd *cmd, sector_t sector);
>>   #else
>>   static inline int null_zone_init(struct nullb_device *dev)
>>   {
>> @@ -111,6 +111,6 @@ static inline void null_zone_write(struct nullb_cmd *cmd, sector_t sector,
>>   				   unsigned int nr_sectors)
>>   {
>>   }
>> -static inline void null_zone_reset(struct nullb_cmd *cmd, sector_t sector) {}
>> +static inline void null_zone_mgmt_op(struct nullb_cmd *cmd, sector_t sector) {}
>>   #endif /* CONFIG_BLK_DEV_ZONED */
>>   #endif /* __NULL_BLK_H */
>> diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
>> index 447d635c79a2..5058fb980c9c 100644
>> --- a/drivers/block/null_blk_main.c
>> +++ b/drivers/block/null_blk_main.c
>> @@ -1209,10 +1209,17 @@ static blk_status_t null_handle_cmd(struct nullb_cmd *cmd)
>>   			nr_sectors = blk_rq_sectors(cmd->rq);
>>   		}
>>   
>> -		if (op == REQ_OP_WRITE)
>> +		switch (op) {
>> +		case REQ_OP_WRITE:
>>   			null_zone_write(cmd, sector, nr_sectors);
>> -		else if (op == REQ_OP_ZONE_RESET)
>> -			null_zone_reset(cmd, sector);
>> +			break;
>> +		case REQ_OP_ZONE_RESET:
>> +		case REQ_OP_ZONE_OPEN:
>> +		case REQ_OP_ZONE_CLOSE:
>> +		case REQ_OP_ZONE_FINISH:
>> +			null_zone_mgmt_op(cmd, sector);
>> +			break;
>> +		}
>>   	}
>>   out:
>>   	/* Complete IO by inline, softirq or timer */
>> diff --git a/drivers/block/null_blk_zoned.c b/drivers/block/null_blk_zoned.c
>> index fca0c97ff1aa..47d956b2e148 100644
>> --- a/drivers/block/null_blk_zoned.c
>> +++ b/drivers/block/null_blk_zoned.c
>> @@ -121,17 +121,44 @@ void null_zone_write(struct nullb_cmd *cmd, sector_t sector,
>>   	}
>>   }
>>   
>> -void null_zone_reset(struct nullb_cmd *cmd, sector_t sector)
>> +void null_zone_mgmt_op(struct nullb_cmd *cmd, sector_t sector)
>>   {
>>   	struct nullb_device *dev = cmd->nq->dev;
>>   	unsigned int zno = null_zone_no(dev, sector);
>>   	struct blk_zone *zone = &dev->zones[zno];
>> +	enum req_opf op = req_op(cmd->rq);
>>   
>>   	if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL) {
>>   		cmd->error = BLK_STS_IOERR;
>>   		return;
>>   	}
>>   
>> -	zone->cond = BLK_ZONE_COND_EMPTY;
>> -	zone->wp = zone->start;
>> +	switch (op) {
>> +	case REQ_OP_ZONE_RESET:
>> +		zone->cond = BLK_ZONE_COND_EMPTY;
>> +		zone->wp = zone->start;
>> +		return;
>> +	case REQ_OP_ZONE_OPEN:
>> +		if (zone->cond == BLK_ZONE_COND_FULL) {
>> +			cmd->error = BLK_STS_IOERR;
>> +			return;
>> +		}
>> +		zone->cond = BLK_ZONE_COND_EXP_OPEN;
> 
> 
> With ZBC, open of a full zone is a "nop". No error. So I would rather have this as:
> 
> 		if (zone->cond != BLK_ZONE_COND_FULL)
> 			zone->cond = BLK_ZONE_COND_EXP_OPEN;
> 		
Is this only ZBC? I can't find a reference to it in ZAC. I think it 
should fail. One is trying to open a zone that is full, one can't open 
it again. It's done for this round.
> 
>> +		return;
>> +	case REQ_OP_ZONE_CLOSE:
>> +		if (zone->cond == BLK_ZONE_COND_FULL) {
>> +			cmd->error = BLK_STS_IOERR;
>> +			return;
>> +		}
>> +		zone->cond = BLK_ZONE_COND_CLOSED;
> 
> Sam as for open. Closing a full zone on ZBC is a nop. 

I think this should cause error.

And the code above would
> also set an empty zone to closed. Finally, if the zone is open but nothing was
> written to it, it must be returned to empty condition, not closed. 

Only on a reset event right? In general, if I do a expl. open, close it, 
it should not go to empty.

So something
> like this is needed.
> 
> 		switch (zone->cond) {
> 		case BLK_ZONE_COND_FULL:
> 		case BLK_ZONE_COND_EMPTY:
> 			break;
> 		case BLK_ZONE_COND_EXP_OPEN:
> 			if (zone->wp == zone->start) {
> 				zone->cond = BLK_ZONE_COND_EMPTY;
> 				break;
> 			}
> 		/* fallthrough */
> 		default:
> 			zone->cond = BLK_ZONE_COND_CLOSED;
> 		}
> 
>> +		return;
>> +	case REQ_OP_ZONE_FINISH:
>> +		zone->cond = BLK_ZONE_COND_FULL;
>> +		zone->wp = zone->start + zone->len;
>> +		return;
>> +	default:
>> +		/* Invalid zone condition */
>> +		cmd->error = BLK_STS_IOERR;
>> +		return;
>> +	}
>>   }
>>
> 
>