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Subject: Re: [PATCH v5 04/17] device-dax/kmem: replace release_resource() with
 release_mem_region()
To:     Dan Williams <dan.j.williams@intel.com>, akpm@linux-foundation.org
Cc:     Vishal Verma <vishal.l.verma@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Brice Goglin <Brice.Goglin@inria.fr>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>, Jia He <justin.he@arm.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        linux-mm@kvack.org, linux-nvdimm@lists.01.org,
        linux-kernel@vger.kernel.org
References: <160106109960.30709.7379926726669669398.stgit@dwillia2-desk3.amr.corp.intel.com>
 <160106112239.30709.15909567572288425294.stgit@dwillia2-desk3.amr.corp.intel.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <86f450e7-d1a7-3d82-b486-afd6682c5942@redhat.com>
Date:   Wed, 30 Sep 2020 18:23:21 +0200
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In-Reply-To: <160106112239.30709.15909567572288425294.stgit@dwillia2-desk3.amr.corp.intel.com>
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Precedence: bulk

On 25.09.20 21:12, Dan Williams wrote:
> Towards removing the mode specific @dax_kmem_res attribute from the
> generic 'struct dev_dax', and preparing for multi-range support, change
> the kmem driver to use the idiomatic release_mem_region() to pair with
> the initial request_mem_region(). This also eliminates the need to open
> code the release of the resource allocated by request_mem_region().
> 
> As there are no more dax_kmem_res users, delete this struct member.
> 
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Brice Goglin <Brice.Goglin@inria.fr>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Jia He <justin.he@arm.com>
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/dax/dax-private.h |    3 ---
>  drivers/dax/kmem.c        |   20 +++++++-------------
>  2 files changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
> index 6779f683671d..12a2dbc43b40 100644
> --- a/drivers/dax/dax-private.h
> +++ b/drivers/dax/dax-private.h
> @@ -42,8 +42,6 @@ struct dax_region {
>   * @dev - device core
>   * @pgmap - pgmap for memmap setup / lifetime (driver owned)
>   * @range: resource range for the instance
> - * @dax_mem_res: physical address range of hotadded DAX memory
> - * @dax_mem_name: name for hotadded DAX memory via add_memory_driver_managed()
>   */
>  struct dev_dax {
>  	struct dax_region *region;
> @@ -52,7 +50,6 @@ struct dev_dax {
>  	struct device dev;
>  	struct dev_pagemap *pgmap;
>  	struct range range;
> -	struct resource *dax_kmem_res;
>  };
>  
>  static inline u64 range_len(struct range *range)
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 6fe2cb1c5f7c..e56fc688bdc5 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -33,7 +33,7 @@ int dev_dax_kmem_probe(struct device *dev)
>  {
>  	struct dev_dax *dev_dax = to_dev_dax(dev);
>  	struct range range = dax_kmem_range(dev_dax);
> -	struct resource *new_res;
> +	struct resource *res;
>  	char *res_name;
>  	int numa_node;
>  	int rc;
> @@ -56,8 +56,8 @@ int dev_dax_kmem_probe(struct device *dev)
>  		return -ENOMEM;
>  
>  	/* Region is permanently reserved if hotremove fails. */
> -	new_res = request_mem_region(range.start, range_len(&range), res_name);
> -	if (!new_res) {
> +	res = request_mem_region(range.start, range_len(&range), res_name);
> +	if (!res) {
>  		dev_warn(dev, "could not reserve region [%#llx-%#llx]\n", range.start, range.end);
>  		kfree(res_name);
>  		return -EBUSY;
> @@ -69,23 +69,20 @@ int dev_dax_kmem_probe(struct device *dev)
>  	 * inherit flags from the parent since it may set new flags
>  	 * unknown to us that will break add_memory() below.
>  	 */
> -	new_res->flags = IORESOURCE_SYSTEM_RAM;
> +	res->flags = IORESOURCE_SYSTEM_RAM;
>  
>  	/*
>  	 * Ensure that future kexec'd kernels will not treat this as RAM
>  	 * automatically.
>  	 */
> -	rc = add_memory_driver_managed(numa_node, new_res->start,
> -				       resource_size(new_res), kmem_name);
> +	rc = add_memory_driver_managed(numa_node, range.start, range_len(&range), kmem_name);
>  	if (rc) {
> -		release_resource(new_res);
> -		kfree(new_res);
> +		release_mem_region(range.start, range_len(&range));
>  		kfree(res_name);
>  		return rc;
>  	}
>  
>  	dev_set_drvdata(dev, res_name);
> -	dev_dax->dax_kmem_res = new_res;
>  
>  	return 0;
>  }
> @@ -95,7 +92,6 @@ 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;
>  	const char *res_name = dev_get_drvdata(dev);
>  	int rc;
>  
> @@ -114,10 +110,8 @@ static int dev_dax_kmem_remove(struct device *dev)
>  	}
>  
>  	/* Release and free dax resources */
> -	release_resource(res);
> -	kfree(res);
> +	release_mem_region(range.start, range_len(&range));

Does that work? AFAIKs,

__release_region(&iomem_resource, (start), (n)) -> __release_region()

will only remove stuff that is IORESOURCE_BUSY.

Maybe storing it in drvdata is indeed the easiest way to remove it from
struct dax_region.

-- 
Thanks,

David / dhildenb