diff mbox series

[v7,02/13] block: allow blk-zoned devices to have non-power-of-2 zone size

Message ID 20220615101920.329421-3-p.raghav@samsung.com (mailing list archive)
State New, archived
Headers show
Series [v7,01/13] block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2 zsze | expand

Commit Message

Pankaj Raghav June 15, 2022, 10:19 a.m. UTC 
Checking if a given sector is aligned to a zone is a common
operation that is performed for zoned devices. Add
blk_queue_is_zone_start helper to check for this instead of opencoding it
everywhere.

Convert the calculations on zone size to be generic instead of relying on
power_of_2 based logic in the block layer using the helpers wherever
possible.

The only hot path affected by this change for power_of_2 zoned devices
is in blk_check_zone_append() but blk_queue_is_zone_start() helper is
used to optimize the calculation for po2 zone sizes. Note that the append
path cannot be accessed by direct raw access to the block device but only
through a filesystem abstraction.

Finally, allow non power of 2 zoned devices provided that their zone
capacity and zone size are equal. The main motivation to allow non
power_of_2 zoned device is to remove the unmapped LBA between zcap and
zsze for devices that cannot have a power_of_2 zcap.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 block/blk-core.c       |  3 +--
 block/blk-zoned.c      | 25 +++++++++++++++++++------
 include/linux/blkdev.h | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 8 deletions(-)

Comments

Bart Van Assche June 15, 2022, 8:28 p.m. UTC | #1 
On 6/15/22 03:19, Pankaj Raghav wrote:
> @@ -489,14 +489,27 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
>   	 * smaller last zone.
>   	 */
>   	if (zone->start == 0) {
> -		if (zone->len == 0 || !is_power_of_2(zone->len)) {
> -			pr_warn("%s: Invalid zoned device with non power of two zone size (%llu)\n",
> -				disk->disk_name, zone->len);
> +		if (zone->len == 0) {
> +			pr_warn("%s: Invalid zone size", disk->disk_name);
> +			return -ENODEV;
> +		}
> +
> +		/*
> +		 * Don't allow zoned device with non power_of_2 zone size with
> +		 * zone capacity less than zone size.
> +		 */

Please change "power_of_2" into "power-of-2".

> +		if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
> +			pr_warn("%s: Invalid zone capacity for non power of 2 zone size",
> +				disk->disk_name);
>   			return -ENODEV;
>   		}

The above check seems wrong to me. I don't see why devices that report a 
capacity that is less than the zone size should be rejected.

> +		/*
> +		 * Division is used to calculate nr_zones for both power_of_2
> +		 * and non power_of_2 zone sizes as it is not in the hot path.
> +		 */

Shouldn't the above comment be moved to the patch description? I'm not 
sure whether having such a comment in the source code is valuable.

> +static inline sector_t blk_queue_offset_from_zone_start(struct request_queue *q,
> +							sector_t sec)
> +{
> +	sector_t zone_sectors = blk_queue_zone_sectors(q);
> +	u64 remainder = 0;
> +
> +	if (!blk_queue_is_zoned(q))
> +		return false;

"return false" should only occur in functions returning a boolean. This 
function returns type sector_t.

Thanks,

Bart.
Pankaj Raghav June 16, 2022, 10:09 a.m. UTC | #2 
On 2022-06-15 22:28, Bart Van Assche wrote:
isk_name, zone->len);
>> +        if (zone->len == 0) {
>> +            pr_warn("%s: Invalid zone size", disk->disk_name);
>> +            return -ENODEV;
>> +        }
>> +
>> +        /*
>> +         * Don't allow zoned device with non power_of_2 zone size with
>> +         * zone capacity less than zone size.
>> +         */
> 

> Please change "power_of_2" into "power-of-2".
> 
Ok.
>> +        if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
>> +            pr_warn("%s: Invalid zone capacity for non power of 2
>> zone size",
>> +                disk->disk_name);
>>               return -ENODEV;
>>           }
> 
> The above check seems wrong to me. I don't see why devices that report a
> capacity that is less than the zone size should be rejected.
> 
This was brought up by Damien during previous reviews. The argument was
that the reason to allow non power-of-2 zoned device is to remove the
gaps between zone size and zone capacity. Allowing a npo2 zone size with
a different capacity, even though it is technically possible, it does
not make any practical sense. That is why this check was introduced.
Does that answer your question?
>> +        /*
>> +         * Division is used to calculate nr_zones for both power_of_2
>> +         * and non power_of_2 zone sizes as it is not in the hot path.
>> +         */
> 
> Shouldn't the above comment be moved to the patch description? I'm not
> sure whether having such a comment in the source code is valuable.
> 
Yeah, I will remove it. Maybe it is very obvious at this point.
>> +static inline sector_t blk_queue_offset_from_zone_start(struct
>> request_queue *q,
>> +                            sector_t sec)
>> +{
>> +    sector_t zone_sectors = blk_queue_zone_sectors(q);
>> +    u64 remainder = 0;
>> +
>> +    if (!blk_queue_is_zoned(q))
>> +        return false;
> 
> "return false" should only occur in functions returning a boolean. This
> function returns type sector_t.
> 
Good catch. It was a copy paste mistake. Fixed it.
> Thanks,
> 
> Bart.
Luis Chamberlain June 16, 2022, 4:04 p.m. UTC | #3 
On Thu, Jun 16, 2022 at 12:09:35PM +0200, Pankaj Raghav wrote:
> On 2022-06-15 22:28, Bart Van Assche wrote:
> >> +        if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
> >> +            pr_warn("%s: Invalid zone capacity for non power of 2
> >> zone size",
> >> +                disk->disk_name);
> >>               return -ENODEV;
> >>           }
> > 
> > The above check seems wrong to me. I don't see why devices that report a
> > capacity that is less than the zone size should be rejected.
> > 
> This was brought up by Damien during previous reviews. The argument was
> that the reason to allow non power-of-2 zoned device is to remove the
> gaps between zone size and zone capacity. Allowing a npo2 zone size with
> a different capacity, even though it is technically possible, it does
> not make any practical sense. That is why this check was introduced.
> Does that answer your question?

Perhaps just add a comment because unless you are involved in the prior
reviews this might not be clear.

  Luis
Damien Le Moal June 16, 2022, 11:30 p.m. UTC | #4 
On 6/16/22 19:09, Pankaj Raghav wrote:
> On 2022-06-15 22:28, Bart Van Assche wrote:
> isk_name, zone->len);
>>> +        if (zone->len == 0) {
>>> +            pr_warn("%s: Invalid zone size", disk->disk_name);
>>> +            return -ENODEV;
>>> +        }
>>> +
>>> +        /*
>>> +         * Don't allow zoned device with non power_of_2 zone size with
>>> +         * zone capacity less than zone size.
>>> +         */
>>
> 
>> Please change "power_of_2" into "power-of-2".
>>
> Ok.
>>> +        if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
>>> +            pr_warn("%s: Invalid zone capacity for non power of 2
>>> zone size",
>>> +                disk->disk_name);
>>>               return -ENODEV;
>>>           }
>>
>> The above check seems wrong to me. I don't see why devices that report a
>> capacity that is less than the zone size should be rejected.
>>
> This was brought up by Damien during previous reviews. The argument was
> that the reason to allow non power-of-2 zoned device is to remove the
> gaps between zone size and zone capacity. Allowing a npo2 zone size with
> a different capacity, even though it is technically possible, it does
> not make any practical sense. That is why this check was introduced.
> Does that answer your question?

Add a comment explaining this restriction, clearly mentioning that it is a
Linux restrictions and not mandated by the specifications.

>>> +        /*
>>> +         * Division is used to calculate nr_zones for both power_of_2
>>> +         * and non power_of_2 zone sizes as it is not in the hot path.
>>> +         */
>>
>> Shouldn't the above comment be moved to the patch description? I'm not
>> sure whether having such a comment in the source code is valuable.
>>
> Yeah, I will remove it. Maybe it is very obvious at this point.
>>> +static inline sector_t blk_queue_offset_from_zone_start(struct
>>> request_queue *q,
>>> +                            sector_t sec)
>>> +{
>>> +    sector_t zone_sectors = blk_queue_zone_sectors(q);
>>> +    u64 remainder = 0;
>>> +
>>> +    if (!blk_queue_is_zoned(q))
>>> +        return false;
>>
>> "return false" should only occur in functions returning a boolean. This
>> function returns type sector_t.
>>
> Good catch. It was a copy paste mistake. Fixed it.
>> Thanks,
>>
>> Bart.
> 
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://listman.redhat.com/mailman/listinfo/dm-devel
diff mbox series

Patch

diff --git a/block/blk-core.c b/block/blk-core.c
index 06ff5bbfe..248b947e5 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -629,8 +629,7 @@  static inline blk_status_t blk_check_zone_append(struct request_queue *q,
 		return BLK_STS_NOTSUPP;
 
 	/* The bio sector must point to the start of a sequential zone */
-	if (pos & (blk_queue_zone_sectors(q) - 1) ||
-	    !blk_queue_zone_is_seq(q, pos))
+	if (!blk_queue_is_zone_start(q, pos) || !blk_queue_zone_is_seq(q, pos))
 		return BLK_STS_IOERR;
 
 	/*
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 8b0615287..7957eec04 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -288,10 +288,10 @@  int blkdev_zone_mgmt(struct block_device *bdev, enum req_opf op,
 		return -EINVAL;
 
 	/* Check alignment (handle eventual smaller last zone) */
-	if (sector & (zone_sectors - 1))
+	if (!blk_queue_is_zone_start(q, sector))
 		return -EINVAL;
 
-	if ((nr_sectors & (zone_sectors - 1)) && end_sector != capacity)
+	if (!blk_queue_is_zone_start(q, nr_sectors) && end_sector != capacity)
 		return -EINVAL;
 
 	/*
@@ -489,14 +489,27 @@  static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
 	 * smaller last zone.
 	 */
 	if (zone->start == 0) {
-		if (zone->len == 0 || !is_power_of_2(zone->len)) {
-			pr_warn("%s: Invalid zoned device with non power of two zone size (%llu)\n",
-				disk->disk_name, zone->len);
+		if (zone->len == 0) {
+			pr_warn("%s: Invalid zone size", disk->disk_name);
+			return -ENODEV;
+		}
+
+		/*
+		 * Don't allow zoned device with non power_of_2 zone size with
+		 * zone capacity less than zone size.
+		 */
+		if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
+			pr_warn("%s: Invalid zone capacity for non power of 2 zone size",
+				disk->disk_name);
 			return -ENODEV;
 		}
 
 		args->zone_sectors = zone->len;
-		args->nr_zones = (capacity + zone->len - 1) >> ilog2(zone->len);
+		/*
+		 * Division is used to calculate nr_zones for both power_of_2
+		 * and non power_of_2 zone sizes as it is not in the hot path.
+		 */
+		args->nr_zones = div64_u64(capacity + zone->len - 1, zone->len);
 	} else if (zone->start + args->zone_sectors < capacity) {
 		if (zone->len != args->zone_sectors) {
 			pr_warn("%s: Invalid zoned device with non constant zone size\n",
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 39017ae9d..3c106dba1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -692,6 +692,27 @@  static inline unsigned int blk_queue_zone_no(struct request_queue *q,
 	return div64_u64(sector, zone_sectors);
 }
 
+static inline sector_t blk_queue_offset_from_zone_start(struct request_queue *q,
+							sector_t sec)
+{
+	sector_t zone_sectors = blk_queue_zone_sectors(q);
+	u64 remainder = 0;
+
+	if (!blk_queue_is_zoned(q))
+		return false;
+
+	if (is_power_of_2(zone_sectors))
+		return sec & (zone_sectors - 1);
+
+	div64_u64_rem(sec, zone_sectors, &remainder);
+	return remainder;
+}
+
+static inline bool blk_queue_is_zone_start(struct request_queue *q, sector_t sec)
+{
+	return blk_queue_offset_from_zone_start(q, sec) == 0;
+}
+
 static inline bool blk_queue_zone_is_seq(struct request_queue *q,
 					 sector_t sector)
 {
@@ -738,6 +759,18 @@  static inline unsigned int blk_queue_zone_no(struct request_queue *q,
 {
 	return 0;
 }
+
+static inline sector_t blk_queue_offset_from_zone_start(struct request_queue *q,
+							sector_t sec)
+{
+	return 0;
+}
+
+static inline bool blk_queue_is_zone_start(struct request_queue *q, sector_t sec)
+{
+	return false;
+}
+
 static inline unsigned int queue_max_open_zones(const struct request_queue *q)
 {
 	return 0;