Re: [PATCH 2/4] null_blk: add zone open, close, and finish support

Matias Bjørling
2019-06-25T13:03:53Z

On 6/25/19 2:36 PM, Damien Le Moal wrote:
> On 2019/06/25 20:06, Matias Bjørling wrote:
>> 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.
>
> Page 52/53, section 5.2.6.3.2:
>
> If the OPEN ALL bit is cleared to zero and the zone specified by the ZONE ID
> field (see 5.2.4.3.3) is in Zone Condition:
> a) EMPTY, IMPLICITLY OPENED, or CLOSED, then the device shall process an
> Explicitly Open Zone function
> (see 4.6.3.4.10) for the zone specified by the ZONE ID field;
> b) EXPLICITLY OPENED or FULL, then the device shall:
> A) not change the zone's state; and
> B) return successful command completion;
>
>>>
>>>> + 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.
>
> See ZAB/ZAC close command description. Same text as above, almost. Not an error.
> It is a nop. ZAC page 48, section 5.2.4.3.2:
>
> If the CLOSE ALL bit is cleared to zero and the zone specified by the ZONE ID
> field (see 5.2.4.3.3) is in Zone Condition:
> a) IMPLICITLY OPENED, or EXPLICITLY OPENED, then the device shall process a
> Close Zone function
> (see 4.6.3.4.11) for the zone specified by the ZONE ID field;
> b) EMPTY, CLOSED, or FULL, then the device shall:
> A) not change the zone's state; and
> B) return successful command completion;
>
>>
>> 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.
>
> See the zone state machine. It does return to empty from expl open if nothing
> was written, that is, if the WP is still at zone start. This text is in ZAC
> section 4.6.3.4.11 as noted above:
>
> For the specified zone, the Zone Condition state machine processing of this
> function (e.g., as shown in the ZC2: Implicit_Open state (see 4.6.3.4.3))
> results in the Zone Condition for the specified zone becoming:
> a) EMPTY, if the write pointer indicates the lowest LBA in the zone and Non
> Sequential Write Resources Active is false; or
> b) CLOSED, if the write pointer does not indicate the lowest LBA in the zone or
> Non-Sequential Write Resources Active is true.
>

Schooled! That is what one gets from having the spec in paper form on
the table ;)

>>
>> 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;
>>>> + }
>>>> }
>>>>
>>>
>>>
>>
>>
>
>