linux-kernel - Re: [PATCH v5 02/17] device-dax/kmem: introduce dax_kmem

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Date:   Wed, 30 Sep 2020 18:14:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>, akpm@...ux-foundation.org
Cc:     Vishal Verma <vishal.l.verma@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Brice Goglin <Brice.Goglin@...ia.fr>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>, Jia He <justin.he@....com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 02/17] device-dax/kmem: introduce dax_kmem_range()

On 25.09.20 21:11, Dan Williams wrote:
> Towards removing the mode specific @dax_kmem_res attribute from the
> generic 'struct dev_dax', and preparing for multi-range support, teach
> the driver to calculate the hotplug range from the device range. The
> hotplug range is the trivially calculated memory-block-size aligned
> version of the device range.
> 
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: Brice Goglin <Brice.Goglin@...ia.fr>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Jia He <justin.he@....com>
> Cc: Joao Martins <joao.m.martins@...cle.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/dax/kmem.c |   40 +++++++++++++++++-----------------------
>  1 file changed, 17 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 5bb133df147d..b0d6a99cf12d 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -19,13 +19,20 @@ static const char *kmem_name;
>  /* Set if any memory will remain added when the driver will be unloaded. */
>  static bool any_hotremove_failed;
>  
> +static struct range dax_kmem_range(struct dev_dax *dev_dax)
> +{
> +	struct range range;
> +
> +	/* memory-block align the hotplug range */
> +	range.start = ALIGN(dev_dax->range.start, memory_block_size_bytes());
> +	range.end = ALIGN_DOWN(dev_dax->range.end + 1, memory_block_size_bytes()) - 1;
> +	return range;
> +}
> +
>  int dev_dax_kmem_probe(struct device *dev)
>  {
>  	struct dev_dax *dev_dax = to_dev_dax(dev);
> -	struct range *range = &dev_dax->range;
> -	resource_size_t kmem_start;
> -	resource_size_t kmem_size;
> -	resource_size_t kmem_end;
> +	struct range range = dax_kmem_range(dev_dax);
>  	struct resource *new_res;
>  	const char *new_res_name;
>  	int numa_node;
> @@ -44,25 +51,14 @@ int dev_dax_kmem_probe(struct device *dev)
>  		return -EINVAL;
>  	}
>  
> -	/* Hotplug starting at the beginning of the next block: */
> -	kmem_start = ALIGN(range->start, memory_block_size_bytes());
> -
> -	kmem_size = range_len(range);
> -	/* Adjust the size down to compensate for moving up kmem_start: */
> -	kmem_size -= kmem_start - range->start;
> -	/* Align the size down to cover only complete blocks: */
> -	kmem_size &= ~(memory_block_size_bytes() - 1);
> -	kmem_end = kmem_start + kmem_size;
> -
>  	new_res_name = kstrdup(dev_name(dev), GFP_KERNEL);
>  	if (!new_res_name)
>  		return -ENOMEM;
>  
>  	/* Region is permanently reserved if hotremove fails. */
> -	new_res = request_mem_region(kmem_start, kmem_size, new_res_name);
> +	new_res = request_mem_region(range.start, range_len(&range), new_res_name);
>  	if (!new_res) {
> -		dev_warn(dev, "could not reserve region [%pa-%pa]\n",
> -			 &kmem_start, &kmem_end);
> +		dev_warn(dev, "could not reserve region [%#llx-%#llx]\n", range.start, range.end);
>  		kfree(new_res_name);
>  		return -EBUSY;
>  	}
> @@ -96,9 +92,8 @@ int dev_dax_kmem_probe(struct device *dev)
>  static int dev_dax_kmem_remove(struct device *dev)
>  {
>  	struct dev_dax *dev_dax = to_dev_dax(dev);
> +	struct range range = dax_kmem_range(dev_dax);
>  	struct resource *res = dev_dax->dax_kmem_res;
> -	resource_size_t kmem_start = res->start;
> -	resource_size_t kmem_size = resource_size(res);
>  	const char *res_name = res->name;
>  	int rc;
>  
> @@ -108,12 +103,11 @@ static int dev_dax_kmem_remove(struct device *dev)
>  	 * there is no way to hotremove this memory until reboot because device
>  	 * unbind will succeed even if we return failure.
>  	 */
> -	rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
> +	rc = remove_memory(dev_dax->target_node, range.start, range_len(&range));
>  	if (rc) {
>  		any_hotremove_failed = true;
> -		dev_err(dev,
> -			"DAX region %pR cannot be hotremoved until the next reboot\n",
> -			res);
> +		dev_err(dev, "%#llx-%#llx cannot be hotremoved until the next reboot\n",
> +				range.start, range.end);
>  		return rc;
>  	}
>  
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb