Re: [PATCH v7] ndctl: Add support for get bus and region persistence domain

[Dan Williams <dan.j.williams@intel.com>]

On Wed, Mar 21, 2018 at 12:55 PM, Dave Jiang <dave.jiang@intel.com> wrote:
> Adding helper functions to iterate through sysfs region persistence domain
> attribute. The region will display the domain with the most persistence for the
> region.  The bus will display the domain attribute with the least persistence
> amongst all the regions. ndctl_bus_get_persistence_domain() and
> ndctl_region_get_persistence_domain are exported. ndctl list will also display
> the region persistence domain as well.
>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
> v7:
> - set attrib to unknown when no attrib detected instead of none. will add
>   support of none attrib in kernel at a later time.
>
> v6:
> - emit "none" when there's nothing in sysfs attrib, and "unknown" when there
>   is no sysfs attrib at all.
> - Use sysfs_read_attr() to retrieve domain values
> - Change INT32_MAX to INT_MAX.
>
> v5:
> - space out ndctl_persistence_domain for future attributes
>
> v4:
> - change enum ndctl_persistence to enum ndctl_persistence_domain
>
> v3:
> - fixed up return types per Ross's comments
> - removed persistence_domain for bus and calculate on the fly per Dan's comment
>
> v2:
> - Simplied scanning of persistence domain from Ross's comments.
>
>  ndctl/lib/libndctl.c   |   88 ++++++++++++++++++++++++++++++++++++++++++++++++
>  ndctl/lib/libndctl.sym |    2 +
>  ndctl/libndctl.h       |   13 +++++++
>  ndctl/list.c           |   20 +++++++++++
>  4 files changed, 123 insertions(+)
>
> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> index a165e697..991042df 100644
> --- a/ndctl/lib/libndctl.c
> +++ b/ndctl/lib/libndctl.c
> @@ -180,6 +180,7 @@ struct ndctl_region {
>         } iset;
>         FILE *badblocks;
>         struct badblock bb;
> +       enum ndctl_persistence_domain persistence_domain;
>  };
>
>  /**
> @@ -916,6 +917,22 @@ NDCTL_EXPORT struct ndctl_bus *ndctl_bus_get_by_provider(struct ndctl_ctx *ctx,
>         return NULL;
>  }
>
> +NDCTL_EXPORT enum ndctl_persistence_domain
> +ndctl_bus_get_persistence_domain(struct ndctl_bus *bus)
> +{
> +       struct ndctl_region *region;
> +       enum ndctl_persistence_domain pd = PERSISTENCE_UNKNOWN;
> +
> +       /* iterate through region to get the region persistence domain */
> +       ndctl_region_foreach(bus, region) {
> +               /* we are looking for the least persistence domain */
> +               if (pd > region->persistence_domain)

If I'm reading this right it will never return anything other than
PERSISTENCE_UNKNOWN because nothing is greater than INT_MAX. It seems
this should start at -1 and then be the max of all regions. If it's
still -1 at the end of the loop then return PERSISTENCE_UNKNOWN
otherwise the max.
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