Re: [ndctl PATCH] libndctl: Update nvdimm flags after inject-smart

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

On Tue, Jul 13, 2021 at 1:25 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote:
>
> Presently after performing a inject-smart the nvdimm flags reported are out
> of date as shown below where no 'smart_notify' or 'flush_fail' flags were
> reported even though they are set after injecting the smart error:
>
> $ sudo inject-smart -fU nmem0
> [
>   {
>     "dev":"nmem0",
>     "health":{
>       "health_state":"fatal",
>       "shutdown_state":"dirty",
>       "shutdown_count":0
>     }
>   }
> ]
> $ sudo cat /sys/class/nd/ndctl0/device/nmem0/papr/flags
> flush_fail smart_notify
>
> This happens because nvdimm flags are only parsed once during its probe and
> not refreshed even after a inject-smart operation makes them out of
> date. To fix this the patch adds a new export from libndctl named as
> ndctl_refresh_dimm_flags() that can be called after inject-smart that
> forces a refresh of nvdimm flags. This ensures that correct nvdimm flags
> are reported after the inject-smart operation as shown below:
>
> $ sudo ndctl inject-smart -fU nmem0
> [
>   {
>     "dev":"nmem0",
>     "flag_failed_flush":true,
>     "flag_smart_event":true,
>     "health":{
>       "health_state":"fatal",
>       "shutdown_state":"dirty",
>       "shutdown_count":0
>     }
>   }
> ]
>
> The patch refactors populate_dimm_attributes() to move the nvdimm flags
> parsing code to the newly introduced ndctl_refresh_dimm_flags()
> export. Since reading nvdimm flags requires constructing path using
> 'bus_prefix' which is only available during add_dimm(), the patch
> introduces a new member 'struct ndctl_dimm.bus_prefix' to cache its
> value. During ndctl_refresh_dimm_flags() the cached bus_prefix is used to
> read the contents of the nvdimm flag file and pass it on to the appropriate
> flag parsing function.

I think this can be handled without needing an explicit
ndctl_refresh_dimm_flags() api. Teach all the flag retrieval apis to
check if the cached value has been invalidated and re-parse the flags.
Then teach the inject-smart path to invalidate the cached copy of the
flags.