linux-kernel - Re: [PATCH v9 12/13] dm: introduce DM_EMULATED

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Date:   Wed, 10 Aug 2022 10:16:42 -0700
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Pankaj Raghav <p.raghav@...sung.com>, Johannes.Thumshirn@....com,
        snitzer@...nel.org, axboe@...nel.dk, agk@...hat.com, hch@....de
Cc:     dm-devel@...hat.com, matias.bjorling@....com, gost.dev@...sung.com,
        linux-kernel@...r.kernel.org, pankydev8@...il.com,
        jaegeuk@...nel.org, hare@...e.de, linux-block@...r.kernel.org,
        linux-nvme@...ts.infradead.org, bvanassche@....org
Subject: Re: [PATCH v9 12/13] dm: introduce DM_EMULATED_ZONES target type

On 2022/08/03 2:48, Pankaj Raghav wrote:
> Introduce a new target type DM_EMULATED_ZONES for targets with
> a different zone number of sectors than the underlying device zone
> number of sectors.

"zone number of sectors" is strange. "number of sectors per zone (aka zone
size)" is simpler and clear.

> 
> This target type is introduced as the existing zoned targets assume
> that the target and the underlying device have the same zone
> number of sectors. The new target: dm-po2zone will use this new target
> type as it emulates the zone boundary that is different from the
> underlying zoned device.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>

With that text fixed, looks OK to me.

Reviewed-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>

> ---
>  drivers/md/dm-table.c         | 13 ++++++++++---
>  include/linux/device-mapper.h |  9 +++++++++
>  2 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 31eb1d29d136..b37991ea3ffb 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -1614,13 +1614,20 @@ static bool dm_table_supports_zoned_model(struct dm_table *t,
>  	return true;
>  }
>  
> -static int device_not_matches_zone_sectors(struct dm_target *ti, struct dm_dev *dev,
> +/*
> + * Callback function to check for device zone sector across devices. If the
> + * DM_TARGET_EMULATED_ZONES target feature flag is not set, then the target
> + * should have the same zone sector as the underlying devices.
> + */
> +static int check_valid_device_zone_sectors(struct dm_target *ti, struct dm_dev *dev,
>  					   sector_t start, sector_t len, void *data)
>  {
>  	unsigned int *zone_sectors = data;
>  
> -	if (!bdev_is_zoned(dev->bdev))
> +	if (!bdev_is_zoned(dev->bdev) ||
> +	    dm_target_supports_emulated_zones(ti->type))
>  		return 0;
> +
>  	return bdev_zone_sectors(dev->bdev) != *zone_sectors;
>  }
>  
> @@ -1645,7 +1652,7 @@ static int validate_hardware_zoned_model(struct dm_table *t,
>  	if (!zone_sectors)
>  		return -EINVAL;
>  
> -	if (dm_table_any_dev_attr(t, device_not_matches_zone_sectors, &zone_sectors)) {
> +	if (dm_table_any_dev_attr(t, check_valid_device_zone_sectors, &zone_sectors)) {
>  		DMERR("%s: zone sectors is not consistent across all zoned devices",
>  		      dm_device_name(t->md));
>  		return -EINVAL;
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 04c6acf7faaa..83e20de264c9 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -294,6 +294,15 @@ struct target_type {
>  #define dm_target_supports_mixed_zoned_model(type) (false)
>  #endif
>  
> +#ifdef CONFIG_BLK_DEV_ZONED
> +#define DM_TARGET_EMULATED_ZONES	0x00000400
> +#define dm_target_supports_emulated_zones(type) \
> +	((type)->features & DM_TARGET_EMULATED_ZONES)
> +#else
> +#define DM_TARGET_EMULATED_ZONES	0x00000000
> +#define dm_target_supports_emulated_zones(type) (false)
> +#endif
> +
>  struct dm_target {
>  	struct dm_table *table;
>  	struct target_type *type;


-- 
Damien Le Moal
Western Digital Research