Re: [PATCH 2/2] ndctl, intel: Fallback to smart cached shutdown_count

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Tue, 2018-08-07 at 16:26 -0600, Keith Busch wrote:
> A user space rule saves the unsafe shutdown count to a fixed location
> for Intel dimms so that non-root users can read it. If the smart command
> submission fails, this patch uses that saved value in a newly added
> ndctl_cmd "handle_error" callback.  If the cached value is available,
> the error handler will override the command status to success, and set
> the valid flags for the shutdown count.
> 
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
>  ndctl/lib/intel.c    | 34 +++++++++++++++++++++++++++++++++-
>  ndctl/lib/libndctl.c |  2 ++
>  ndctl/lib/private.h  |  1 +
>  3 files changed, 36 insertions(+), 1 deletion(-)

Looks good to me!

> 
> diff --git a/ndctl/lib/intel.c b/ndctl/lib/intel.c
> index 0abea1e..83f8203 100644
> --- a/ndctl/lib/intel.c
> +++ b/ndctl/lib/intel.c
> @@ -56,6 +56,38 @@ static struct ndctl_cmd *alloc_intel_cmd(struct ndctl_dimm *dimm,
>  	return cmd;
>  }
>  
> +/*
> + * If provided, read the cached shutdown count in case the user does not have
> + * access rights to run the smart command, and pretend the command was
> + * successful with only the shutdown_count valid.
> + */
> +static int intel_smart_handle_error(struct ndctl_cmd *cmd)
> +{
> +	struct ndctl_dimm *dimm = cmd->dimm;
> +	char *path = NULL, shutdown_count[16] = {};
> +	int fd, rc = cmd->status;
> +
> +	if (asprintf(&path, DEF_TMPFS_DIR "/%s/usc",
> +		     ndctl_dimm_get_unique_id(dimm)) < 0)
> +		return rc;
> +
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0)
> +		goto free_path;
> +
> +	if (read(fd, shutdown_count, sizeof(shutdown_count)) < 0)
> +		goto close;
> +
> +	cmd->intel->smart.flags = ND_INTEL_SMART_SHUTDOWN_COUNT_VALID;
> +	cmd->intel->smart.shutdown_count = strtoull(shutdown_count, NULL, 0);
> +	rc = cmd->status = 0;
> + close:
> +	close (fd);
> + free_path:
> +	free(path);
> +	return rc;
> +}
> +
>  static struct ndctl_cmd *intel_dimm_cmd_new_smart(struct ndctl_dimm *dimm)
>  {
>  	struct ndctl_cmd *cmd;
> @@ -67,7 +99,7 @@ static struct ndctl_cmd *intel_dimm_cmd_new_smart(struct ndctl_dimm *dimm)
>  	if (!cmd)
>  		return NULL;
>  	cmd->firmware_status = &cmd->intel->smart.status;
> -
> +	cmd->handle_error = intel_smart_handle_error;
>  	return cmd;
>  }
>  
> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> index 47e005e..d94321e 100644
> --- a/ndctl/lib/libndctl.c
> +++ b/ndctl/lib/libndctl.c
> @@ -2651,6 +2651,8 @@ NDCTL_EXPORT int ndctl_cmd_submit(struct ndctl_cmd *cmd)
>  	close(fd);
>   out:
>  	cmd->status = rc;
> +	if (rc && cmd->handle_error)
> +		rc = cmd->handle_error(cmd);
>  	return rc;
>  }
>  
> diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
> index a94f894..5812c85 100644
> --- a/ndctl/lib/private.h
> +++ b/ndctl/lib/private.h
> @@ -255,6 +255,7 @@ struct ndctl_cmd {
>  		int dir;
>  	} iter;
>  	struct ndctl_cmd *source;
> +	int (*handle_error)(struct ndctl_cmd *cmd);
>  	union {
>  		struct nd_cmd_ars_cap ars_cap[0];
>  		struct nd_cmd_ars_start ars_start[0];
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