Re: [PATCH v2] acpi, nfit: Further restrict userspace ARS start requests

[Dave Jiang <dave.jiang@intel.com>]

On 10/15/2018 02:00 PM, Dan Williams wrote:
> In addition to not allowing ARS start while the background thread is
> actively running, prevent ARS start while any scrub request is pending.
> 
> This aligns the window for ARS start submission with the status of ARS
> reported via sysfs. Previously userspace could sneak its own ARS start
> requests in while sysfs reported -EBUSY.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
> Changes in v2:
> * Require acpi_desc->scrub_spa to be NULL to prevent requests being sent
>   while a scrub is active, or whose results are waiting to be reaped.
> 
>  drivers/acpi/nfit/core.c |   19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index f7efcd9843e0..253c0e85554d 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -3364,6 +3364,8 @@ static int __acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
>  		struct nvdimm *nvdimm, unsigned int cmd)
>  {
>  	struct acpi_nfit_desc *acpi_desc = to_acpi_nfit_desc(nd_desc);
> +	struct nfit_spa *nfit_spa;
> +	int rc = 0;
>  
>  	if (nvdimm)
>  		return 0;
> @@ -3373,13 +3375,20 @@ static int __acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
>  	/*
>  	 * The kernel and userspace may race to initiate a scrub, but
>  	 * the scrub thread is prepared to lose that initial race.  It
> -	 * just needs guarantees that any ars it initiates are not
> -	 * interrupted by any intervening start reqeusts from userspace.
> +	 * just needs guarantees that any ARS it initiates are not
> +	 * interrupted by any intervening start requests from userspace.
>  	 */
> -	if (work_busy(&acpi_desc->dwork.work))
> -		return -EBUSY;
> +	mutex_lock(&acpi_desc->init_mutex);
> +	list_for_each_entry(nfit_spa, &acpi_desc->spas, list)
> +		if (acpi_desc->scrub_spa
> +				|| test_bit(ARS_REQ_SHORT, &nfit_spa->ars_state)
> +				|| test_bit(ARS_REQ_LONG, &nfit_spa->ars_state)) {
> +			rc = -EBUSY;
> +			break;
> +		}
> +	mutex_unlock(&acpi_desc->init_mutex);
>  
> -	return 0;
> +	return rc;
>  }
>  
>  /* prevent security commands from being issued via ioctl */
> 
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