[PATCH v4 00/13] support non power of 2 zoned devices

[PATCH v4 00/13] support non power of 2 zoned devices

[Pankaj Raghav]

- Background and Motivation:

The zone storage implementation in Linux, introduced since v4.10, first
targetted SMR drives which have a power of 2 (po2) zone size alignment
requirement. The po2 zone size was further imposed implicitly by the
block layer's blk_queue_chunk_sectors(), used to prevent IO merging
across chunks beyond the specified size, since v3.16 through commit
762380ad9322 ("block: add notion of a chunk size for request merging").
But this same general block layer po2 requirement for blk_queue_chunk_sectors()
was removed on v5.10 through commit 07d098e6bbad ("block: allow 'chunk_sectors'
to be non-power-of-2").

NAND, which is the media used in newer zoned storage devices, does not
naturally align to po2. In these devices, zone cap is not the same as the
po2 zone size. When the zone cap != zone size, then unmapped LBAs are
introduced to cover the space between the zone cap and zone size. po2
requirement does not make sense for these type of zone storage devices.
This patch series aims to remove these unmapped LBAs for zoned devices when
zone cap is npo2. This is done by relaxing the po2 zone size constraint
in the kernel and allowing zoned device with npo2 zone sizes if zone cap
== zone size.

Removing the po2 requirement from zone storage should be possible
now provided that no userspace regression and no performance regressions are
introduced. Stop-gap patches have been already merged into f2fs-tools to
proactively not allow npo2 zone sizes until proper support is added [0].
Additional kernel stop-gap patches are provided in this series for dm-zoned.
Support for npo2 zonefs and btrfs support is addressed in this series.

There was an effort previously [1] to add support to non po2 devices via
device level emulation but that was rejected with a final conclusion
to add support for non po2 zoned device in the complete stack[2].

- Patchset description:
This patchset aims at adding support to non power of 2 zoned devices in
the block layer, nvme layer, null blk and adds support to btrfs and
zonefs.

This round of patches **will not** support DM layer for non
power of 2 zoned devices. More about this in the future work section.

Patches 1-2 deals with removing the po2 constraint from the
block layer.

Patches 3-4 deals with removing the constraint from nvme zns.

Patches 5-9 adds support to btrfs for non po2 zoned devices.

Patch 10 removes the po2 constraint in ZoneFS

Patch 11-12 removes the po2 contraint in null blk

Patches 13 adds conditions to not allow non power of 2 devices in
DM.

The patch series is based on linux-next tag: next-20220502

- Performance:
PO2 zone sizes utilizes log and shifts instead of division when
determing alignment, zone number, etc. The same math cannot be used when
using a zoned device with non po2 zone size. Hence, to avoid any performance
regression on zoned devices with po2 zone sizes, the optimized math in the
hot paths has been retained with branching.

The performance was measured using null blk for regression
and the results have been posted in the appropriate commit log. No
performance regression was noticed.

- Testing
With respect to testing we need to tackle two things: one for regression
on po2 zoned device and progression on non po2 zoned devices.

kdevops (https://github.com/mcgrof/kdevops) was extensively used to
automate the testing for blktests and (x)fstests for btrfs changes. The
known failures were excluded during the test based on the baseline
v5.17.0-rc7

-- regression
Emulated zoned device with zone size =128M , nr_zones = 10000

Block and nvme zns:
blktests were run with no new failures

Btrfs:
Changes were tested with the following profile in QEMU:
[btrfs_simple_zns]
TEST_DIR=<dir>
SCRATCH_MNT=<mnt>
FSTYP=btrfs
MKFS_OPTIONS="-f -d single -m single"
TEST_DEV=<dev>
SCRATCH_DEV_POOL=<dev-pool>

No new failures were observed in btrfs, generic and shared test suite

ZoneFS:
zonefs-tests-nullblk.sh and zonefs-tests.sh from zonefs-tools were run
with no failures.

nullblk:
t/zbd/run-tests-against-nullb from fio was run with no failures.

DM:
It was verified if dm-zoned successfully mounts without any
error.

-- progression
Emulated zoned device with zone size = 96M , nr_zones = 10000

Block and nvme zns:
blktests were run with no new failures

Btrfs:
Same profile as po2 zone size was used.

Many tests in xfstests for btrfs included dm-flakey and some tests
required dm-linear. As they are not supported at the moment for non
po2 devices, those **tests were excluded for non po2 devices**.

No new failures were observed in btrfs, generic and shared test suite

ZoneFS:
zonefs-tests.sh from zonefs-tools were run with no failures.

nullblk:
A new section was added to cover non po2 devices:

section14()
{
       conv_pcnt=10
       zone_size=3
       zone_capacity=3
       max_open=${set_max_open}
       zbd_test_opts+=("-o ${max_open}")
}
t/zbd/run-tests-against-nullb from fio was run with no failures.

DM:
It was verified that dm-zoned does not mount.

- Tools:
Some tools had to be updated to support non po2 devices. Once these
patches are accepted in the kernel, these tool updates will also be
upstreamed.
* btrfs-prog: https://github.com/Panky-codes/btrfs-progs/tree/remove-po2-btrfs
* blkzone: https://github.com/Panky-codes/util-linux/tree/remove-po2
* zonefs-tools: https://github.com/Panky-codes/zonefs-tools/tree/remove-po2

- Future work
To reduce the amount of changes and testing, support for DM was
excluded in this round of patches. The plan is to add support to F2FS
and DM in the forthcoming future.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git/commit/?h=dev-test&id=6afcf6493578e77528abe65ab8b12f3e1c16749f
[1] https://lore.kernel.org/all/20220310094725.GA28499@lst.de/T/
[2] https://lore.kernel.org/all/20220315135245.eqf4tqngxxb7ymqa@unifi/

Changes since v1:
- Put the function declaration and its usage in the same commit (Bart)
- Remove bdev_zone_aligned function (Bart)
- Change the name from blk_queue_zone_aligned to blk_queue_is_zone_start
  (Damien)
- q is never null in from bdev_get_queue (Damien)
- Add condition during bringup and check for zsze == zcap for npo2
  drives (Damien)
- Rounddown operation should be made generic to work in 32 bits arch
  (bart)
- Add comments where generic calculation is directly used instead having
  special handling for po2 zone sizes (Hannes)
- Make the minimum zone size alignment requirement for btrfs to be 1M
  instead of BTRFS_STRIPE_LEN(David)

Changes since v2:
- Minor formatting changes

Changes since v3:
- Make superblock mirror align with the existing superblock log offsets
  (David)
- DM change return value and remove extra newline (Damien and Mike)
- Optimize null blk zone index lookup with shift for po2 zone size
  (Damien)

Luis Chamberlain (1):
  dm-zoned: ensure only power of 2 zone sizes are allowed

Pankaj Raghav (12):
  block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2
    zsze
  block: allow blk-zoned devices to have non-power-of-2 zone size
  nvme: zns: Allow ZNS drives that have non-power_of_2 zone size
  nvmet: Allow ZNS target to support non-power_of_2 zone sizes
  btrfs: zoned: Cache superblock location in btrfs_zoned_device_info
  btrfs: zoned: Make sb_zone_number function non power of 2 compatible
  btrfs: zoned: use generic btrfs zone helpers to support npo2 zoned
    devices
  btrfs:zoned: make sb for npo2 zone devices align with sb log offsets
  btrfs: zoned: relax the alignment constraint for zoned devices
  zonefs: allow non power of 2 zoned devices
  null_blk: allow non power of 2 zoned devices
  null_blk: use zone_size_sects_shift for power of 2 zoned devices

 block/blk-core.c                  |   3 +-
 block/blk-zoned.c                 |  40 +++++--
 drivers/block/null_blk/main.c     |   5 +-
 drivers/block/null_blk/null_blk.h |   6 +
 drivers/block/null_blk/zoned.c    |  20 ++--
 drivers/md/dm-zone.c              |  12 ++
 drivers/nvme/host/zns.c           |  24 ++--
 drivers/nvme/target/zns.c         |   2 +-
 fs/btrfs/volumes.c                |  24 ++--
 fs/btrfs/zoned.c                  | 191 +++++++++++++++++++++---------
 fs/btrfs/zoned.h                  |  44 ++++++-
 fs/zonefs/super.c                 |   6 +-
 fs/zonefs/zonefs.h                |   1 -
 include/linux/blkdev.h            |  37 +++++-
 14 files changed, 303 insertions(+), 112 deletions(-)

-- 
2.25.1

[PATCH v4 01/13] block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2 zsze

[Pankaj Raghav]

Adapt blkdev_nr_zones and blk_queue_zone_no function so that it can
also work for non-power-of-2 zone sizes.

As the existing deployments of zoned devices had power-of-2
assumption, power-of-2 optimized calculation is kept for those devices.

There are no direct hot paths modified and the changes just
introduce one new branch per call.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 block/blk-zoned.c      | 13 ++++++++++---
 include/linux/blkdev.h |  8 +++++++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 38cd840d8..140230134 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -111,16 +111,23 @@ EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
  * blkdev_nr_zones - Get number of zones
  * @disk:	Target gendisk
  *
- * Return the total number of zones of a zoned block device.  For a block
- * device without zone capabilities, the number of zones is always 0.
+ * Return the total number of zones of a zoned block device, including the
+ * eventual small last zone if present. For a block device without zone
+ * capabilities, the number of zones is always 0.
  */
 unsigned int blkdev_nr_zones(struct gendisk *disk)
 {
 	sector_t zone_sectors = blk_queue_zone_sectors(disk->queue);
+	sector_t capacity = get_capacity(disk);
 
 	if (!blk_queue_is_zoned(disk->queue))
 		return 0;
-	return (get_capacity(disk) + zone_sectors - 1) >> ilog2(zone_sectors);
+
+	if (is_power_of_2(zone_sectors))
+		return (capacity + zone_sectors - 1) >>
+		       ilog2(zone_sectors);
+
+	return div64_u64(capacity + zone_sectors - 1, zone_sectors);
 }
 EXPORT_SYMBOL_GPL(blkdev_nr_zones);
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1b24c1fb3..22fe512ee 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -675,9 +675,15 @@ static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
 static inline unsigned int blk_queue_zone_no(struct request_queue *q,
 					     sector_t sector)
 {
+	sector_t zone_sectors = blk_queue_zone_sectors(q);
+
 	if (!blk_queue_is_zoned(q))
 		return 0;
-	return sector >> ilog2(q->limits.chunk_sectors);
+
+	if (is_power_of_2(zone_sectors))
+		return sector >> ilog2(zone_sectors);
+
+	return div64_u64(sector, zone_sectors);
 }
 
 static inline bool blk_queue_zone_is_seq(struct request_queue *q,
-- 
2.25.1

Re: [PATCH v4 01/13] block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2 zsze

[Damien Le Moal]

On 2022/05/16 15:39, Pankaj Raghav wrote:
> Adapt blkdev_nr_zones and blk_queue_zone_no function so that it can
> also work for non-power-of-2 zone sizes.
> 
> As the existing deployments of zoned devices had power-of-2
> assumption, power-of-2 optimized calculation is kept for those devices.
> 
> There are no direct hot paths modified and the changes just
> introduce one new branch per call.
> 
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  block/blk-zoned.c      | 13 ++++++++++---
>  include/linux/blkdev.h |  8 +++++++-
>  2 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 38cd840d8..140230134 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -111,16 +111,23 @@ EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
>   * blkdev_nr_zones - Get number of zones
>   * @disk:	Target gendisk
>   *
> - * Return the total number of zones of a zoned block device.  For a block
> - * device without zone capabilities, the number of zones is always 0.
> + * Return the total number of zones of a zoned block device, including the
> + * eventual small last zone if present. For a block device without zone
> + * capabilities, the number of zones is always 0.
>   */
>  unsigned int blkdev_nr_zones(struct gendisk *disk)
>  {
>  	sector_t zone_sectors = blk_queue_zone_sectors(disk->queue);
> +	sector_t capacity = get_capacity(disk);
>  
>  	if (!blk_queue_is_zoned(disk->queue))
>  		return 0;
> -	return (get_capacity(disk) + zone_sectors - 1) >> ilog2(zone_sectors);
> +
> +	if (is_power_of_2(zone_sectors))
> +		return (capacity + zone_sectors - 1) >>
> +		       ilog2(zone_sectors);

Why the line break here ? This fits on one line, no ?

> +
> +	return div64_u64(capacity + zone_sectors - 1, zone_sectors);
>  }
>  EXPORT_SYMBOL_GPL(blkdev_nr_zones);
>  
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 1b24c1fb3..22fe512ee 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -675,9 +675,15 @@ static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
>  static inline unsigned int blk_queue_zone_no(struct request_queue *q,
>  					     sector_t sector)
>  {
> +	sector_t zone_sectors = blk_queue_zone_sectors(q);
> +
>  	if (!blk_queue_is_zoned(q))
>  		return 0;
> -	return sector >> ilog2(q->limits.chunk_sectors);
> +
> +	if (is_power_of_2(zone_sectors))
> +		return sector >> ilog2(zone_sectors);
> +
> +	return div64_u64(sector, zone_sectors);
>  }
>  
>  static inline bool blk_queue_zone_is_seq(struct request_queue *q,


-- 
Damien Le Moal
Western Digital Research

[PATCH v4 02/13] block: allow blk-zoned devices to have non-power-of-2 zone size

[Pankaj Raghav]

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>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 block/blk-core.c       |  3 +--
 block/blk-zoned.c      | 27 +++++++++++++++++++++------
 include/linux/blkdev.h | 22 ++++++++++++++++++++++
 3 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index f305cb66c..b7051b7ea 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -634,8 +634,7 @@ 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 140230134..cfc2fb804 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -289,10 +289,10 @@ 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;
 
 	/*
@@ -490,14 +490,29 @@ 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 zoned size with non power of 2 zone size and zone capacity < 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 22fe512ee..32d7bd7b1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -686,6 +686,22 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
 	return div64_u64(sector, zone_sectors);
 }
 
+static inline bool blk_queue_is_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 IS_ALIGNED(sec, zone_sectors);
+
+	div64_u64_rem(sec, zone_sectors, &remainder);
+	/* if there is a remainder, then the sector is not aligned */
+	return remainder == 0;
+}
+
 static inline bool blk_queue_zone_is_seq(struct request_queue *q,
 					 sector_t sector)
 {
@@ -732,6 +748,12 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
 {
 	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;
-- 
2.25.1

Re: [PATCH v4 02/13] block: allow blk-zoned devices to have non-power-of-2 zone size

[Damien Le Moal]

On 2022/05/16 15:39, Pankaj Raghav wrote:
> 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>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  block/blk-core.c       |  3 +--
>  block/blk-zoned.c      | 27 +++++++++++++++++++++------
>  include/linux/blkdev.h | 22 ++++++++++++++++++++++
>  3 files changed, 44 insertions(+), 8 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index f305cb66c..b7051b7ea 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -634,8 +634,7 @@ 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 140230134..cfc2fb804 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -289,10 +289,10 @@ 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;
>  
>  	/*
> @@ -490,14 +490,29 @@ 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);

This fits on one line, no ?

> +			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 zoned size with non power of 2 zone size and zone capacity < zone size",
> +				disk->disk_name);

Very long... What about:

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.
> +		 */

This comment is not very useful.

> +		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 22fe512ee..32d7bd7b1 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -686,6 +686,22 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
>  	return div64_u64(sector, zone_sectors);
>  }
>  
> +static inline bool blk_queue_is_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 IS_ALIGNED(sec, zone_sectors);
> +
> +	div64_u64_rem(sec, zone_sectors, &remainder);
> +	/* if there is a remainder, then the sector is not aligned */

Hmmm... Fairly obvious. Not sure this comment is useful.

> +	return remainder == 0;
> +}
> +
>  static inline bool blk_queue_zone_is_seq(struct request_queue *q,
>  					 sector_t sector)
>  {
> @@ -732,6 +748,12 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
>  {
>  	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;


-- 
Damien Le Moal
Western Digital Research

[PATCH v4 03/13] nvme: zns: Allow ZNS drives that have non-power_of_2 zone size

[Pankaj Raghav]

Remove the condition which disallows non-power_of_2 zone size ZNS drive
to be updated and use generic method to calculate number of zones
instead of relying on log and shift based calculation on zone size.

The power_of_2 calculation has been replaced directly with generic
calculation without special handling. Both modified functions are not
used in hot paths, they are only used during initialization &
revalidation of the ZNS device.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 drivers/nvme/host/zns.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
index 9f81beb4d..65d2aa68a 100644
--- a/drivers/nvme/host/zns.c
+++ b/drivers/nvme/host/zns.c
@@ -101,13 +101,6 @@ int nvme_update_zone_info(struct nvme_ns *ns, unsigned lbaf)
 	}
 
 	ns->zsze = nvme_lba_to_sect(ns, le64_to_cpu(id->lbafe[lbaf].zsze));
-	if (!is_power_of_2(ns->zsze)) {
-		dev_warn(ns->ctrl->device,
-			"invalid zone size:%llu for namespace:%u\n",
-			ns->zsze, ns->head->ns_id);
-		status = -ENODEV;
-		goto free_data;
-	}
 
 	blk_queue_set_zoned(ns->disk, BLK_ZONED_HM);
 	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
@@ -128,8 +121,13 @@ static void *nvme_zns_alloc_report_buffer(struct nvme_ns *ns,
 	const size_t min_bufsize = sizeof(struct nvme_zone_report) +
 				   sizeof(struct nvme_zone_descriptor);
 
+	/*
+	 * Division is used to calculate nr_zones with no special handling
+	 * for power of 2 zone sizes as this function is not invoked in a
+	 * hot path
+	 */
 	nr_zones = min_t(unsigned int, nr_zones,
-			 get_capacity(ns->disk) >> ilog2(ns->zsze));
+			 div64_u64(get_capacity(ns->disk), ns->zsze));
 
 	bufsize = sizeof(struct nvme_zone_report) +
 		nr_zones * sizeof(struct nvme_zone_descriptor);
@@ -182,6 +180,7 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
 	int ret, zone_idx = 0;
 	unsigned int nz, i;
 	size_t buflen;
+	u64 remainder = 0;
 
 	if (ns->head->ids.csi != NVME_CSI_ZNS)
 		return -EINVAL;
@@ -197,7 +196,14 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
 	c.zmr.zrasf = NVME_ZRASF_ZONE_REPORT_ALL;
 	c.zmr.pr = NVME_REPORT_ZONE_PARTIAL;
 
-	sector &= ~(ns->zsze - 1);
+	/*
+	 * rounddown the sector value to the nearest zone size. roundown macro
+	 * provided in math.h will not work for 32 bit architectures.
+	 * Division is used here with no special handling for power of 2
+	 * zone sizes as this function is not invoked in a hot path
+	 */
+	div64_u64_rem(sector, ns->zsze, &remainder);
+	sector -= remainder;
 	while (zone_idx < nr_zones && sector < get_capacity(ns->disk)) {
 		memset(report, 0, buflen);
 
-- 
2.25.1

Re: [dm-devel] [PATCH v4 03/13] nvme: zns: Allow ZNS drives that have non-power_of_2 zone size

[Damien Le Moal]

On 2022/05/16 15:39, Pankaj Raghav wrote:
> Remove the condition which disallows non-power_of_2 zone size ZNS drive
> to be updated and use generic method to calculate number of zones
> instead of relying on log and shift based calculation on zone size.
> 
> The power_of_2 calculation has been replaced directly with generic
> calculation without special handling. Both modified functions are not
> used in hot paths, they are only used during initialization &
> revalidation of the ZNS device.
> 
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  drivers/nvme/host/zns.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> index 9f81beb4d..65d2aa68a 100644
> --- a/drivers/nvme/host/zns.c
> +++ b/drivers/nvme/host/zns.c
> @@ -101,13 +101,6 @@ int nvme_update_zone_info(struct nvme_ns *ns, unsigned lbaf)
>  	}
>  
>  	ns->zsze = nvme_lba_to_sect(ns, le64_to_cpu(id->lbafe[lbaf].zsze));
> -	if (!is_power_of_2(ns->zsze)) {
> -		dev_warn(ns->ctrl->device,
> -			"invalid zone size:%llu for namespace:%u\n",
> -			ns->zsze, ns->head->ns_id);
> -		status = -ENODEV;
> -		goto free_data;
> -	}
>  
>  	blk_queue_set_zoned(ns->disk, BLK_ZONED_HM);
>  	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
> @@ -128,8 +121,13 @@ static void *nvme_zns_alloc_report_buffer(struct nvme_ns *ns,
>  	const size_t min_bufsize = sizeof(struct nvme_zone_report) +
>  				   sizeof(struct nvme_zone_descriptor);
>  
> +	/*
> +	 * Division is used to calculate nr_zones with no special handling
> +	 * for power of 2 zone sizes as this function is not invoked in a
> +	 * hot path
> +	 */

Comment not very useful.

>  	nr_zones = min_t(unsigned int, nr_zones,
> -			 get_capacity(ns->disk) >> ilog2(ns->zsze));
> +			 div64_u64(get_capacity(ns->disk), ns->zsze));
>  
>  	bufsize = sizeof(struct nvme_zone_report) +
>  		nr_zones * sizeof(struct nvme_zone_descriptor);
> @@ -182,6 +180,7 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
>  	int ret, zone_idx = 0;
>  	unsigned int nz, i;
>  	size_t buflen;
> +	u64 remainder = 0;
>  
>  	if (ns->head->ids.csi != NVME_CSI_ZNS)
>  		return -EINVAL;
> @@ -197,7 +196,14 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
>  	c.zmr.zrasf = NVME_ZRASF_ZONE_REPORT_ALL;
>  	c.zmr.pr = NVME_REPORT_ZONE_PARTIAL;
>  
> -	sector &= ~(ns->zsze - 1);
> +	/*
> +	 * rounddown the sector value to the nearest zone size. roundown macro
> +	 * provided in math.h will not work for 32 bit architectures.
> +	 * Division is used here with no special handling for power of 2
> +	 * zone sizes as this function is not invoked in a hot path
> +	 */

Please simplify this to:

	/* Round down the sector value to the nearest zone start */

> +	div64_u64_rem(sector, ns->zsze, &remainder);
> +	sector -= remainder;
>  	while (zone_idx < nr_zones && sector < get_capacity(ns->disk)) {
>  		memset(report, 0, buflen);
>  


-- 
Damien Le Moal
Western Digital Research

[PATCH v4 04/13] nvmet: Allow ZNS target to support non-power_of_2 zone sizes

[Pankaj Raghav]

A generic bdev_zone_no helper is added to calculate zone number for a given
sector in a block device. This helper internally uses blk_queue_zone_no to
find the zone number.

Use the helper bdev_zone_no() to calculate nr of zones. This let's us
make modifications to the math if needed in one place and adds now
support for npo2 zone devices.

Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 drivers/nvme/target/zns.c | 2 +-
 include/linux/blkdev.h    | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
index 82b61acf7..5516dd6cc 100644
--- a/drivers/nvme/target/zns.c
+++ b/drivers/nvme/target/zns.c
@@ -242,7 +242,7 @@ static unsigned long nvmet_req_nr_zones_from_slba(struct nvmet_req *req)
 	unsigned int sect = nvmet_lba_to_sect(req->ns, req->cmd->zmr.slba);
 
 	return blkdev_nr_zones(req->ns->bdev->bd_disk) -
-		(sect >> ilog2(bdev_zone_sectors(req->ns->bdev)));
+	       bdev_zone_no(req->ns->bdev, sect);
 }
 
 static unsigned long get_nr_zones_from_buf(struct nvmet_req *req, u32 bufsize)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 32d7bd7b1..967790f51 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1370,6 +1370,13 @@ static inline sector_t bdev_zone_sectors(struct block_device *bdev)
 	return 0;
 }
 
+static inline unsigned int bdev_zone_no(struct block_device *bdev, sector_t sec)
+{
+	struct request_queue *q = bdev_get_queue(bdev);
+
+	return blk_queue_zone_no(q, sec);
+}
+
 static inline unsigned int bdev_max_open_zones(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
-- 
2.25.1

Re: [dm-devel] [PATCH v4 00/13] support non power of 2 zoned devices

[Damien Le Moal]

On 2022/05/16 15:39, Pankaj Raghav wrote:
[...]
> - Patchset description:
> This patchset aims at adding support to non power of 2 zoned devices in
> the block layer, nvme layer, null blk and adds support to btrfs and
> zonefs.
> 
> This round of patches **will not** support DM layer for non
> power of 2 zoned devices. More about this in the future work section.
> 
> Patches 1-2 deals with removing the po2 constraint from the
> block layer.
> 
> Patches 3-4 deals with removing the constraint from nvme zns.
> 
> Patches 5-9 adds support to btrfs for non po2 zoned devices.
> 
> Patch 10 removes the po2 constraint in ZoneFS
> 
> Patch 11-12 removes the po2 contraint in null blk
> 
> Patches 13 adds conditions to not allow non power of 2 devices in
> DM.


Not sure what is going on but I only got the first 4 patches and I do not see
the remaining patches on the lists anywhere.


-- 
Damien Le Moal
Western Digital Research

[PATCH v4 00/13] support non power of 2 zoned devices

[Pankaj Raghav]

- Background and Motivation:

The zone storage implementation in Linux, introduced since v4.10, first
targetted SMR drives which have a power of 2 (po2) zone size alignment
requirement. The po2 zone size was further imposed implicitly by the
block layer's blk_queue_chunk_sectors(), used to prevent IO merging
across chunks beyond the specified size, since v3.16 through commit
762380ad9322 ("block: add notion of a chunk size for request merging").
But this same general block layer po2 requirement for blk_queue_chunk_sectors()
was removed on v5.10 through commit 07d098e6bbad ("block: allow 'chunk_sectors'
to be non-power-of-2").

NAND, which is the media used in newer zoned storage devices, does not
naturally align to po2. In these devices, zone cap is not the same as the
po2 zone size. When the zone cap != zone size, then unmapped LBAs are
introduced to cover the space between the zone cap and zone size. po2
requirement does not make sense for these type of zone storage devices.
This patch series aims to remove these unmapped LBAs for zoned devices when
zone cap is npo2. This is done by relaxing the po2 zone size constraint
in the kernel and allowing zoned device with npo2 zone sizes if zone cap
== zone size.

Removing the po2 requirement from zone storage should be possible
now provided that no userspace regression and no performance regressions are
introduced. Stop-gap patches have been already merged into f2fs-tools to
proactively not allow npo2 zone sizes until proper support is added [0].
Additional kernel stop-gap patches are provided in this series for dm-zoned.
Support for npo2 zonefs and btrfs support is addressed in this series.

There was an effort previously [1] to add support to non po2 devices via
device level emulation but that was rejected with a final conclusion
to add support for non po2 zoned device in the complete stack[2].

- Patchset description:
This patchset aims at adding support to non power of 2 zoned devices in
the block layer, nvme layer, null blk and adds support to btrfs and
zonefs.

This round of patches **will not** support DM layer for non
power of 2 zoned devices. More about this in the future work section.

Patches 1-2 deals with removing the po2 constraint from the
block layer.

Patches 3-4 deals with removing the constraint from nvme zns.

Patches 5-9 adds support to btrfs for non po2 zoned devices.

Patch 10 removes the po2 constraint in ZoneFS

Patch 11-12 removes the po2 contraint in null blk

Patches 13 adds conditions to not allow non power of 2 devices in
DM.

The patch series is based on linux-next tag: next-20220502

- Performance:
PO2 zone sizes utilizes log and shifts instead of division when
determing alignment, zone number, etc. The same math cannot be used when
using a zoned device with non po2 zone size. Hence, to avoid any performance
regression on zoned devices with po2 zone sizes, the optimized math in the
hot paths has been retained with branching.

The performance was measured using null blk for regression
and the results have been posted in the appropriate commit log. No
performance regression was noticed.

- Testing
With respect to testing we need to tackle two things: one for regression
on po2 zoned device and progression on non po2 zoned devices.

kdevops (https://github.com/mcgrof/kdevops) was extensively used to
automate the testing for blktests and (x)fstests for btrfs changes. The
known failures were excluded during the test based on the baseline
v5.17.0-rc7

-- regression
Emulated zoned device with zone size =128M , nr_zones = 10000

Block and nvme zns:
blktests were run with no new failures

Btrfs:
Changes were tested with the following profile in QEMU:
[btrfs_simple_zns]
TEST_DIR=<dir>
SCRATCH_MNT=<mnt>
FSTYP=btrfs
MKFS_OPTIONS="-f -d single -m single"
TEST_DEV=<dev>
SCRATCH_DEV_POOL=<dev-pool>

No new failures were observed in btrfs, generic and shared test suite

ZoneFS:
zonefs-tests-nullblk.sh and zonefs-tests.sh from zonefs-tools were run
with no failures.

nullblk:
t/zbd/run-tests-against-nullb from fio was run with no failures.

DM:
It was verified if dm-zoned successfully mounts without any
error.

-- progression
Emulated zoned device with zone size = 96M , nr_zones = 10000

Block and nvme zns:
blktests were run with no new failures

Btrfs:
Same profile as po2 zone size was used.

Many tests in xfstests for btrfs included dm-flakey and some tests
required dm-linear. As they are not supported at the moment for non
po2 devices, those **tests were excluded for non po2 devices**.

No new failures were observed in btrfs, generic and shared test suite

ZoneFS:
zonefs-tests.sh from zonefs-tools were run with no failures.

nullblk:
A new section was added to cover non po2 devices:

section14()
{
       conv_pcnt=10
       zone_size=3
       zone_capacity=3
       max_open=${set_max_open}
       zbd_test_opts+=("-o ${max_open}")
}
t/zbd/run-tests-against-nullb from fio was run with no failures.

DM:
It was verified that dm-zoned does not mount.

- Tools:
Some tools had to be updated to support non po2 devices. Once these
patches are accepted in the kernel, these tool updates will also be
upstreamed.
* btrfs-prog: https://github.com/Panky-codes/btrfs-progs/tree/remove-po2-btrfs
* blkzone: https://github.com/Panky-codes/util-linux/tree/remove-po2
* zonefs-tools: https://github.com/Panky-codes/zonefs-tools/tree/remove-po2

- Future work
To reduce the amount of changes and testing, support for DM was
excluded in this round of patches. The plan is to add support to F2FS
and DM in the forthcoming future.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git/commit/?h=dev-test&id=6afcf6493578e77528abe65ab8b12f3e1c16749f
[1] https://lore.kernel.org/all/20220310094725.GA28499@lst.de/T/
[2] https://lore.kernel.org/all/20220315135245.eqf4tqngxxb7ymqa@unifi/

Changes since v1:
- Put the function declaration and its usage in the same commit (Bart)
- Remove bdev_zone_aligned function (Bart)
- Change the name from blk_queue_zone_aligned to blk_queue_is_zone_start
  (Damien)
- q is never null in from bdev_get_queue (Damien)
- Add condition during bringup and check for zsze == zcap for npo2
  drives (Damien)
- Rounddown operation should be made generic to work in 32 bits arch
  (bart)
- Add comments where generic calculation is directly used instead having
  special handling for po2 zone sizes (Hannes)
- Make the minimum zone size alignment requirement for btrfs to be 1M
  instead of BTRFS_STRIPE_LEN(David)

Changes since v2:
- Minor formatting changes

Changes since v3:
- Make superblock mirror align with the existing superblock log offsets
  (David)
- DM change return value and remove extra newline
- Optimize null blk zone index lookup with shift for po2 zone size

Luis Chamberlain (1):
  dm-zoned: ensure only power of 2 zone sizes are allowed

Pankaj Raghav (12):
  block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2
    zsze
  block: allow blk-zoned devices to have non-power-of-2 zone size
  nvme: zns: Allow ZNS drives that have non-power_of_2 zone size
  nvmet: Allow ZNS target to support non-power_of_2 zone sizes
  btrfs: zoned: Cache superblock location in btrfs_zoned_device_info
  btrfs: zoned: Make sb_zone_number function non power of 2 compatible
  btrfs: zoned: use generic btrfs zone helpers to support npo2 zoned
    devices
  btrfs:zoned: make sb for npo2 zone devices align with sb log offsets
  btrfs: zoned: relax the alignment constraint for zoned devices
  zonefs: allow non power of 2 zoned devices
  null_blk: allow non power of 2 zoned devices
  null_blk: use zone_size_sects_shift for power of 2 zoned devices

 block/blk-core.c                  |   3 +-
 block/blk-zoned.c                 |  40 +++++--
 drivers/block/null_blk/main.c     |   5 +-
 drivers/block/null_blk/null_blk.h |   6 +
 drivers/block/null_blk/zoned.c    |  20 ++--
 drivers/md/dm-zone.c              |  12 ++
 drivers/nvme/host/zns.c           |  24 ++--
 drivers/nvme/target/zns.c         |   2 +-
 fs/btrfs/volumes.c                |  24 ++--
 fs/btrfs/zoned.c                  | 191 +++++++++++++++++++++---------
 fs/btrfs/zoned.h                  |  44 ++++++-
 fs/zonefs/super.c                 |   6 +-
 fs/zonefs/zonefs.h                |   1 -
 include/linux/blkdev.h            |  37 +++++-
 14 files changed, 303 insertions(+), 112 deletions(-)

-- 
2.25.1

Re: [PATCH v4 00/13] support non power of 2 zoned devices

[Christoph Hellwig]

I'm a little surprised about all this activity.

I though the conclusion at LSF/MM was that for Linux itself there
is very little benefit in supporting this scheme.  It will massively
fragment the supported based of devices and applications, while only
having the benefit of supporting some Samsung legacy devices.

So my impression was that this work, while technically feasible, is
rather useless.  So unless I missed something important I have no
interest in supporting this in NVMe.

Re: [PATCH v4 00/13] support non power of 2 zoned devices

[Javier González]

On 17.05.2022 10:10, Christoph Hellwig wrote:
>I'm a little surprised about all this activity.
>
>I though the conclusion at LSF/MM was that for Linux itself there
>is very little benefit in supporting this scheme.  It will massively
>fragment the supported based of devices and applications, while only
>having the benefit of supporting some Samsung legacy devices.

I believed we had agreed that non-power-of-2 zoned devices was something
to explore. Let me summarize the 3 main points we covered at different
times at LSF/MM:

   - This is not for legacy Samsung ZNS devices. At least 4 other
     vendors have reported building non-power-of-2 ZNS devices to meet
     customer demands on removing holes in the address space. It seems
     like there will be more ZNS devices with size=capacity out there
     than with PO2 sizes. Block device and FS support is very desirable
     for these.

   - We also talked about how the capacity not being a PO2 is the one
     introducing the fragmentation, as applications that already worked
     with SMR HDDs will have to change their data placement policy. The
     size is just a construction, but the real work is adopting the
     capacity.

   - Besides the previous poit, the fragmentation will happen from the
     moment we have available devices. This is not a kernel-only issue.
     We have SMR, ZNS, and soon another spec for zone devices. I
     understood that as long as we do not break any existing support, we
     would be able to expend the zoned ecosystem in Linux.

>So my impression was that this work, while technically feasible, is
>rather useless.  So unless I missed something important I have no
>interest in supporting this in NVMe.

Does the above help you reconsidering your interest in supporting this
in NVMe?

Re: [PATCH v4 00/13] support non power of 2 zoned devices

[Christoph Hellwig]

On Tue, May 17, 2022 at 11:18:34AM +0200, Javier González wrote:
> Does the above help you reconsidering your interest in supporting this
> in NVMe?

Very little.  It just seems like a really bad idea.

Re: [PATCH v4 00/13] support non power of 2 zoned devices

[Javier González]

> On 18 May 2022, at 10.16, Christoph Hellwig <hch@lst.de> wrote:
> 
> On Tue, May 17, 2022 at 11:18:34AM +0200, Javier González wrote:
>> Does the above help you reconsidering your interest in supporting this
>> in NVMe?
> 
> Very little.  It just seems like a really bad idea.

I understand you don’t like this, but I still hope you see value in supporting it. We are getting close to a very minimal patchset, which is also helping to fix bugs in the zoned stack.

If you take a look at the last version abs give some feedback, I’m sure we can end up with a good solution. 

Can you help?