Re: [PATCH 2/5] btrfs: export the device allocation_hint property in sysfs

[Josef Bacik <josef@toxicpanda.com>]

On Sun, Mar 06, 2022 at 07:14:40PM +0100, Goffredo Baroncelli wrote:
> From: Goffredo Baroncelli <kreijack@inwind.it>
> 
> Export the device allocation_hint property via
> /sys/fs/btrfs/<uuid>/devinfo/<devid>/allocation_hint
> 
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  fs/btrfs/sysfs.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 17389a42a3ab..59d92a385a96 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -1578,6 +1578,36 @@ static ssize_t btrfs_devinfo_error_stats_show(struct kobject *kobj,
>  }
>  BTRFS_ATTR(devid, error_stats, btrfs_devinfo_error_stats_show);
>  
> +
> +struct allocation_hint_name_t {
> +	const char *name;
> +	const u64 value;
> +} allocation_hint_name[] = {
> +	{ "DATA_PREFERRED", BTRFS_DEV_ALLOCATION_HINT_DATA_PREFERRED },
> +	{ "METADATA_PREFERRED", BTRFS_DEV_ALLOCATION_HINT_METADATA_PREFERRED },
> +	{ "DATA_ONLY", BTRFS_DEV_ALLOCATION_HINT_DATA_ONLY },
> +	{ "METADATA_ONLY", BTRFS_DEV_ALLOCATION_HINT_METADATA_ONLY },
> +};
> +

The ktest robot complained about this, but also we don't need to be this clever,
also it looks better to have the flags first with standard tabbing.

struct allocation_hint_name {
	const u64 val;
	const char *name;
};

static struct allocation_hint_name allocation_hints[] = {
	{ BTRFS_DEV_ALLOCATION_HINT_DATA_PREFERRED,	"DATA_PREFERRED"	},
	{ BTRFS_DEV_ALLOCATION_HINT_METADATA_PREFERRED,	"METADATA_PREFERRED"	},
	...
};


> +static ssize_t btrfs_devinfo_allocation_hint_show(struct kobject *kobj,
> +					struct kobj_attribute *a, char *buf)
> +{
> +	int i;
> +	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
> +						   devid_kobj);
> +
> +	for (i = 0 ; i < ARRAY_SIZE(allocation_hint_name) ; i++) {
> +		if ((device->type & BTRFS_DEV_ALLOCATION_HINT_MASK) !=
> +		    allocation_hint_name[i].value)
> +			continue;
> +
> +		return scnprintf(buf, PAGE_SIZE, "%s\n",
> +			allocation_hint_name[i].name);
> +	}
> +	return scnprintf(buf, PAGE_SIZE, "<UNKNOWN>\n");

Since we have fs'es that won't use this you should just spit out "NONE".
Thanks,

Josef