Re: [PATCH v6 02/12] cxl/region: Drop redundant pmem region release handling

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu, 01 Dec 2022 13:33:32 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> Now that a cxl_nvdimm object can only experience ->remove() via an
> unregistration event (because the cxl_nvdimm bind attributes are
> suppressed), additional cleanups are possible.
> 
> It is already the case that the removal of a cxl_memdev object triggers
> ->remove() on any associated region. With that mechanism in place there  
> is no need for the cxl_nvdimm removal to trigger the same. Just rely on
> cxl_region_detach() to tear down the whole cxl_pmem_region.
> 
> Tested-by: Robert Richter <rrichter@amd.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Seems logical. There was a bunch of stuff left in some of this where I didn't
follow why it was still there, but that's an artifact of how the series is built
up which is fair enough. FWIW

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/cxl/core/pmem.c |    2 -
>  drivers/cxl/cxl.h       |    1 -
>  drivers/cxl/pmem.c      |   90 -----------------------------------------------
>  3 files changed, 93 deletions(-)
> 
> diff --git a/drivers/cxl/core/pmem.c b/drivers/cxl/core/pmem.c
> index 36aa5070d902..1d12a8206444 100644
> --- a/drivers/cxl/core/pmem.c
> +++ b/drivers/cxl/core/pmem.c
> @@ -188,7 +188,6 @@ static void cxl_nvdimm_release(struct device *dev)
>  {
>  	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
>  
> -	xa_destroy(&cxl_nvd->pmem_regions);
>  	kfree(cxl_nvd);
>  }
>  
> @@ -231,7 +230,6 @@ static struct cxl_nvdimm *cxl_nvdimm_alloc(struct cxl_memdev *cxlmd)
>  
>  	dev = &cxl_nvd->dev;
>  	cxl_nvd->cxlmd = cxlmd;
> -	xa_init(&cxl_nvd->pmem_regions);
>  	device_initialize(dev);
>  	lockdep_set_class(&dev->mutex, &cxl_nvdimm_key);
>  	device_set_pm_not_required(dev);
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 7d07127eade3..4ac7938eaf6c 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -424,7 +424,6 @@ struct cxl_nvdimm {
>  	struct device dev;
>  	struct cxl_memdev *cxlmd;
>  	struct cxl_nvdimm_bridge *bridge;
> -	struct xarray pmem_regions;
>  };
>  
>  struct cxl_pmem_region_mapping {
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 946e171e7d4a..652f00fc68ca 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -27,26 +27,7 @@ static void clear_exclusive(void *cxlds)
>  
>  static void unregister_nvdimm(void *nvdimm)
>  {
> -	struct cxl_nvdimm *cxl_nvd = nvdimm_provider_data(nvdimm);
> -	struct cxl_nvdimm_bridge *cxl_nvb = cxl_nvd->bridge;
> -	struct cxl_pmem_region *cxlr_pmem;
> -	unsigned long index;
> -
> -	device_lock(&cxl_nvb->dev);
> -	dev_set_drvdata(&cxl_nvd->dev, NULL);
> -	xa_for_each(&cxl_nvd->pmem_regions, index, cxlr_pmem) {
> -		get_device(&cxlr_pmem->dev);
> -		device_unlock(&cxl_nvb->dev);
> -
> -		device_release_driver(&cxlr_pmem->dev);
> -		put_device(&cxlr_pmem->dev);
> -
> -		device_lock(&cxl_nvb->dev);
> -	}
> -	device_unlock(&cxl_nvb->dev);
> -
>  	nvdimm_delete(nvdimm);
> -	cxl_nvd->bridge = NULL;
>  }
>  
>  static int cxl_nvdimm_probe(struct device *dev)
> @@ -243,21 +224,6 @@ static int cxl_nvdimm_release_driver(struct device *dev, void *cxl_nvb)
>  	return 0;
>  }
>  
> -static int cxl_pmem_region_release_driver(struct device *dev, void *cxl_nvb)
> -{
> -	struct cxl_pmem_region *cxlr_pmem;
> -
> -	if (!is_cxl_pmem_region(dev))
> -		return 0;
> -
> -	cxlr_pmem = to_cxl_pmem_region(dev);
> -	if (cxlr_pmem->bridge != cxl_nvb)
> -		return 0;
> -
> -	device_release_driver(dev);
> -	return 0;
> -}
> -
>  static void offline_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb,
>  			       struct nvdimm_bus *nvdimm_bus)
>  {
> @@ -269,8 +235,6 @@ static void offline_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb,
>  	 * nvdimm_bus_unregister() rips the nvdimm objects out from
>  	 * underneath them.
>  	 */
> -	bus_for_each_dev(&cxl_bus_type, NULL, cxl_nvb,
> -			 cxl_pmem_region_release_driver);
>  	bus_for_each_dev(&cxl_bus_type, NULL, cxl_nvb,
>  			 cxl_nvdimm_release_driver);
>  	nvdimm_bus_unregister(nvdimm_bus);
> @@ -378,48 +342,6 @@ static void unregister_nvdimm_region(void *nd_region)
>  	nvdimm_region_delete(nd_region);
>  }
>  
> -static int cxl_nvdimm_add_region(struct cxl_nvdimm *cxl_nvd,
> -				 struct cxl_pmem_region *cxlr_pmem)
> -{
> -	int rc;
> -
> -	rc = xa_insert(&cxl_nvd->pmem_regions, (unsigned long)cxlr_pmem,
> -		       cxlr_pmem, GFP_KERNEL);
> -	if (rc)
> -		return rc;
> -
> -	get_device(&cxlr_pmem->dev);
> -	return 0;
> -}
> -
> -static void cxl_nvdimm_del_region(struct cxl_nvdimm *cxl_nvd,
> -				  struct cxl_pmem_region *cxlr_pmem)
> -{
> -	/*
> -	 * It is possible this is called without a corresponding
> -	 * cxl_nvdimm_add_region for @cxlr_pmem
> -	 */
> -	cxlr_pmem = xa_erase(&cxl_nvd->pmem_regions, (unsigned long)cxlr_pmem);
> -	if (cxlr_pmem)
> -		put_device(&cxlr_pmem->dev);
> -}
> -
> -static void release_mappings(void *data)
> -{
> -	int i;
> -	struct cxl_pmem_region *cxlr_pmem = data;
> -	struct cxl_nvdimm_bridge *cxl_nvb = cxlr_pmem->bridge;
> -
> -	device_lock(&cxl_nvb->dev);
> -	for (i = 0; i < cxlr_pmem->nr_mappings; i++) {
> -		struct cxl_pmem_region_mapping *m = &cxlr_pmem->mapping[i];
> -		struct cxl_nvdimm *cxl_nvd = m->cxl_nvd;
> -
> -		cxl_nvdimm_del_region(cxl_nvd, cxlr_pmem);
> -	}
> -	device_unlock(&cxl_nvb->dev);
> -}
> -
>  static void cxlr_pmem_remove_resource(void *res)
>  {
>  	remove_resource(res);
> @@ -508,10 +430,6 @@ static int cxl_pmem_region_probe(struct device *dev)
>  		goto out_nvb;
>  	}
>  
> -	rc = devm_add_action_or_reset(dev, release_mappings, cxlr_pmem);
> -	if (rc)
> -		goto out_nvd;
> -
>  	for (i = 0; i < cxlr_pmem->nr_mappings; i++) {
>  		struct cxl_pmem_region_mapping *m = &cxlr_pmem->mapping[i];
>  		struct cxl_memdev *cxlmd = m->cxlmd;
> @@ -538,14 +456,6 @@ static int cxl_pmem_region_probe(struct device *dev)
>  			goto out_nvd;
>  		}
>  
> -		/*
> -		 * Pin the region per nvdimm device as those may be released
> -		 * out-of-order with respect to the region, and a single nvdimm
> -		 * maybe associated with multiple regions
> -		 */
> -		rc = cxl_nvdimm_add_region(cxl_nvd, cxlr_pmem);
> -		if (rc)
> -			goto out_nvd;
>  		m->cxl_nvd = cxl_nvd;
>  		mappings[i] = (struct nd_mapping_desc) {
>  			.nvdimm = nvdimm,
>