Re: [PATCH v5 6/7] mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()

[Jerome Glisse <jglisse@redhat.com>]

On Wed, Sep 12, 2018 at 07:22:33PM -0700, Dan Williams wrote:
> Commit e8d513483300 "memremap: change devm_memremap_pages interface to
> use struct dev_pagemap" refactored devm_memremap_pages() to allow a
> dev_pagemap instance to be supplied. Passing in a dev_pagemap interface
> simplifies the design of pgmap type drivers in that they can rely on
> container_of() to lookup any private data associated with the given
> dev_pagemap instance.
> 
> In addition to the cleanups this also gives hmm users multi-order-radix
> improvements that arrived with commit ab1b597ee0e4 "mm,
> devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups"
> 
> As part of the conversion to the devm_memremap_pages() method of
> handling the percpu_ref relative to when pages are put, the percpu_ref
> completion needs to move to hmm_devmem_ref_exit(). See commit
> 71389703839e ("mm, zone_device: Replace {get, put}_zone_device_page...")
> for details.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jerome Glisse <jglisse@redhat.com>

> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  mm/hmm.c |  194 ++++++++------------------------------------------------------
>  1 file changed, 26 insertions(+), 168 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index ec1d9eccf176..c6cab5205b99 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -938,17 +938,16 @@ static void hmm_devmem_ref_exit(void *data)
>  	struct hmm_devmem *devmem;
>  
>  	devmem = container_of(ref, struct hmm_devmem, ref);
> +	wait_for_completion(&devmem->completion);
>  	percpu_ref_exit(ref);
>  }
>  
> -static void hmm_devmem_ref_kill(void *data)
> +static void hmm_devmem_ref_kill(struct percpu_ref *ref)
>  {
> -	struct percpu_ref *ref = data;
>  	struct hmm_devmem *devmem;
>  
>  	devmem = container_of(ref, struct hmm_devmem, ref);
>  	percpu_ref_kill(ref);
> -	wait_for_completion(&devmem->completion);
>  }
>  
>  static int hmm_devmem_fault(struct vm_area_struct *vma,
> @@ -971,152 +970,6 @@ static void hmm_devmem_free(struct page *page, void *data)
>  	devmem->ops->free(devmem, page);
>  }
>  
> -static DEFINE_MUTEX(hmm_devmem_lock);
> -static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
> -
> -static void hmm_devmem_radix_release(struct resource *resource)
> -{
> -	resource_size_t key;
> -
> -	mutex_lock(&hmm_devmem_lock);
> -	for (key = resource->start;
> -	     key <= resource->end;
> -	     key += PA_SECTION_SIZE)
> -		radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
> -	mutex_unlock(&hmm_devmem_lock);
> -}
> -
> -static void hmm_devmem_release(void *data)
> -{
> -	struct hmm_devmem *devmem = data;
> -	struct resource *resource = devmem->resource;
> -	unsigned long start_pfn, npages;
> -	struct zone *zone;
> -	struct page *page;
> -
> -	/* pages are dead and unused, undo the arch mapping */
> -	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
> -	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
> -
> -	page = pfn_to_page(start_pfn);
> -	zone = page_zone(page);
> -
> -	mem_hotplug_begin();
> -	if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
> -		__remove_pages(zone, start_pfn, npages, NULL);
> -	else
> -		arch_remove_memory(start_pfn << PAGE_SHIFT,
> -				   npages << PAGE_SHIFT, NULL);
> -	mem_hotplug_done();
> -
> -	hmm_devmem_radix_release(resource);
> -}
> -
> -static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
> -{
> -	resource_size_t key, align_start, align_size, align_end;
> -	struct device *device = devmem->device;
> -	int ret, nid, is_ram;
> -	unsigned long pfn;
> -
> -	align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
> -	align_size = ALIGN(devmem->resource->start +
> -			   resource_size(devmem->resource),
> -			   PA_SECTION_SIZE) - align_start;
> -
> -	is_ram = region_intersects(align_start, align_size,
> -				   IORESOURCE_SYSTEM_RAM,
> -				   IORES_DESC_NONE);
> -	if (is_ram == REGION_MIXED) {
> -		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
> -				__func__, devmem->resource);
> -		return -ENXIO;
> -	}
> -	if (is_ram == REGION_INTERSECTS)
> -		return -ENXIO;
> -
> -	if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
> -		devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
> -	else
> -		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> -
> -	devmem->pagemap.res = *devmem->resource;
> -	devmem->pagemap.page_fault = hmm_devmem_fault;
> -	devmem->pagemap.page_free = hmm_devmem_free;
> -	devmem->pagemap.dev = devmem->device;
> -	devmem->pagemap.ref = &devmem->ref;
> -	devmem->pagemap.data = devmem;
> -
> -	mutex_lock(&hmm_devmem_lock);
> -	align_end = align_start + align_size - 1;
> -	for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
> -		struct hmm_devmem *dup;
> -
> -		dup = radix_tree_lookup(&hmm_devmem_radix,
> -					key >> PA_SECTION_SHIFT);
> -		if (dup) {
> -			dev_err(device, "%s: collides with mapping for %s\n",
> -				__func__, dev_name(dup->device));
> -			mutex_unlock(&hmm_devmem_lock);
> -			ret = -EBUSY;
> -			goto error;
> -		}
> -		ret = radix_tree_insert(&hmm_devmem_radix,
> -					key >> PA_SECTION_SHIFT,
> -					devmem);
> -		if (ret) {
> -			dev_err(device, "%s: failed: %d\n", __func__, ret);
> -			mutex_unlock(&hmm_devmem_lock);
> -			goto error_radix;
> -		}
> -	}
> -	mutex_unlock(&hmm_devmem_lock);
> -
> -	nid = dev_to_node(device);
> -	if (nid < 0)
> -		nid = numa_mem_id();
> -
> -	mem_hotplug_begin();
> -	/*
> -	 * For device private memory we call add_pages() as we only need to
> -	 * allocate and initialize struct page for the device memory. More-
> -	 * over the device memory is un-accessible thus we do not want to
> -	 * create a linear mapping for the memory like arch_add_memory()
> -	 * would do.
> -	 *
> -	 * For device public memory, which is accesible by the CPU, we do
> -	 * want the linear mapping and thus use arch_add_memory().
> -	 */
> -	if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
> -		ret = arch_add_memory(nid, align_start, align_size, NULL,
> -				false);
> -	else
> -		ret = add_pages(nid, align_start >> PAGE_SHIFT,
> -				align_size >> PAGE_SHIFT, NULL, false);
> -	if (ret) {
> -		mem_hotplug_done();
> -		goto error_add_memory;
> -	}
> -	move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
> -				align_start >> PAGE_SHIFT,
> -				align_size >> PAGE_SHIFT, NULL);
> -	mem_hotplug_done();
> -
> -	for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
> -		struct page *page = pfn_to_page(pfn);
> -
> -		page->pgmap = &devmem->pagemap;
> -	}
> -	return 0;
> -
> -error_add_memory:
> -	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
> -error_radix:
> -	hmm_devmem_radix_release(devmem->resource);
> -error:
> -	return ret;
> -}
> -
>  /*
>   * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
>   *
> @@ -1140,6 +993,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  {
>  	struct hmm_devmem *devmem;
>  	resource_size_t addr;
> +	void *result;
>  	int ret;
>  
>  	dev_pagemap_get_ops();
> @@ -1194,14 +1048,18 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  	devmem->pfn_last = devmem->pfn_first +
>  			   (resource_size(devmem->resource) >> PAGE_SHIFT);
>  
> -	ret = hmm_devmem_pages_create(devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> +	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> +	devmem->pagemap.res = *devmem->resource;
> +	devmem->pagemap.page_fault = hmm_devmem_fault;
> +	devmem->pagemap.page_free = hmm_devmem_free;
> +	devmem->pagemap.altmap_valid = false;
> +	devmem->pagemap.ref = &devmem->ref;
> +	devmem->pagemap.data = devmem;
>  
> +	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
> +			hmm_devmem_ref_kill);
> +	if (IS_ERR(result))
> +		return result;
>  	return devmem;
>  }
>  EXPORT_SYMBOL(hmm_devmem_add);
> @@ -1211,6 +1069,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  					   struct resource *res)
>  {
>  	struct hmm_devmem *devmem;
> +	void *result;
>  	int ret;
>  
>  	if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
> @@ -1243,19 +1102,18 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  	devmem->pfn_last = devmem->pfn_first +
>  			   (resource_size(devmem->resource) >> PAGE_SHIFT);
>  
> -	ret = hmm_devmem_pages_create(devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
> -			&devmem->ref);
> -	if (ret)
> -		return ERR_PTR(ret);
> +	devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
> +	devmem->pagemap.res = *devmem->resource;
> +	devmem->pagemap.page_fault = hmm_devmem_fault;
> +	devmem->pagemap.page_free = hmm_devmem_free;
> +	devmem->pagemap.altmap_valid = false;
> +	devmem->pagemap.ref = &devmem->ref;
> +	devmem->pagemap.data = devmem;
>  
> +	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
> +			hmm_devmem_ref_kill);
> +	if (IS_ERR(result))
> +		return result;
>  	return devmem;
>  }
>  EXPORT_SYMBOL(hmm_devmem_add_resource);
>