Re: [PATCH 2/6] btrfs: export the device allocation_hint property in sysfs

[Boris Burkov <boris@bur.io>]

On Fri, Dec 17, 2021 at 07:47:18PM +0100, Goffredo Baroncelli wrote:
> From: Goffredo Baroncelli <kreijack@inwind.it>
> 
> Eport the device allocation_hint property via
> /sys/fs/btrfs/<uuid>/devinfo/<devid>/allocation_hint
> 
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Boris Burkov <boris@bur.io>
> ---
>  fs/btrfs/sysfs.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index beb7f72d50b8..a8d918700d2b 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -1575,6 +1575,17 @@ static ssize_t btrfs_devinfo_error_stats_show(struct kobject *kobj,
>  }
>  BTRFS_ATTR(devid, error_stats, btrfs_devinfo_error_stats_show);
>  
> +static ssize_t btrfs_devinfo_allocation_hint_show(struct kobject *kobj,
> +					struct kobj_attribute *a, char *buf)
> +{
> +	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
> +						   devid_kobj);
> +
> +	return scnprintf(buf, PAGE_SIZE, "0x%08llx\n",
> +		device->type & BTRFS_DEV_ALLOCATION_HINT_MASK );

I think I lightly prefer the string based interface like what was
discussed on V8, but this is fine as well, especially with the progs
change in mind to add the extra usability.

> +}
> +BTRFS_ATTR(devid, allocation_hint, btrfs_devinfo_allocation_hint_show);
> +
>  /*
>   * Information about one device.
>   *
> @@ -1588,6 +1599,7 @@ static struct attribute *devid_attrs[] = {
>  	BTRFS_ATTR_PTR(devid, replace_target),
>  	BTRFS_ATTR_PTR(devid, scrub_speed_max),
>  	BTRFS_ATTR_PTR(devid, writeable),
> +	BTRFS_ATTR_PTR(devid, allocation_hint),
>  	NULL
>  };
>  ATTRIBUTE_GROUPS(devid);
> -- 
> 2.34.1
>