Re: [PATCH 04/26] btrfs-progs: zoned: add new ZONED feature flag

[David Sterba <dsterba@suse.cz>]

On Mon, Apr 26, 2021 at 03:27:20PM +0900, Naohiro Aota wrote:
> With the zoned feature enabled, a zoned block device-aware btrfs allocates
> block groups aligned to the device zones and always write in sequential
> zones at the zone write pointer position.
> 
> It also supports "emulated" zoned mode on a non-zoned device. In the
> emulated mode, btrfs emulates conventional zones by slicing the device with
> a fixed size.
> 
> We don't support conversion from the ext4 volume with the zoned feature
> because we can't be sure all the converted block groups are aligned to zone
> boundaries.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  common/fsfeatures.c        | 8 ++++++++
>  common/fsfeatures.h        | 3 ++-
>  kernel-shared/ctree.h      | 4 +++-
>  kernel-shared/print-tree.c | 1 +
>  4 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/common/fsfeatures.c b/common/fsfeatures.c
> index 569208a9e5b1..c0793339b531 100644
> --- a/common/fsfeatures.c
> +++ b/common/fsfeatures.c
> @@ -100,6 +100,14 @@ static const struct btrfs_feature mkfs_features[] = {
>  		NULL, 0,
>  		NULL, 0,
>  		"RAID1 with 3 or 4 copies" },
> +#ifdef BTRFS_ZONED
> +	{ "zoned", BTRFS_FEATURE_INCOMPAT_ZONED,
> +		"zoned",
> +		NULL, 0,
> +		NULL, 0,
> +		NULL, 0,
> +		"support Zoned devices" },
> +#endif
>  	/* Keep this one last */
>  	{ "list-all", BTRFS_FEATURE_LIST_ALL, NULL }
>  };
> diff --git a/common/fsfeatures.h b/common/fsfeatures.h
> index 74ec2a21caf6..1a7d7f62897f 100644
> --- a/common/fsfeatures.h
> +++ b/common/fsfeatures.h
> @@ -25,7 +25,8 @@
>  		| BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA)
>  
>  /*
> - * Avoid multi-device features (RAID56) and mixed block groups
> + * Avoid multi-device features (RAID56), mixed block groups, and zoned
> + * btrfs
>   */
>  #define BTRFS_CONVERT_ALLOWED_FEATURES				\
>  	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF			\

Looks like BTRFS_FEATURE_INCOMPAT_ZONED should be here.