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Subject: Re: [PATCH v5 03/17] device-dax/kmem: move resource name tracking to
 drvdata
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>
 <160106111639.30709.17624822766862009183.stgit@dwillia2-desk3.amr.corp.intel.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <316f7227-caf9-f207-1dd9-45bb4a6d0fde@redhat.com>
Date:   Wed, 30 Sep 2020 18:19:45 +0200
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Precedence: bulk

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, move
> resource name tracking to driver data.  The memory for the resource name
> needs to have its own lifetime separate from the device bind lifetime
> for cases where the driver is unbound, but the kmem range could not be
> unplugged from the page allocator.
> 
> 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/kmem.c |   16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index b0d6a99cf12d..6fe2cb1c5f7c 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -34,7 +34,7 @@ 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;
> -	const char *new_res_name;
> +	char *res_name;

I wonder why that change ...

>  	int numa_node;
>  	int rc;
>  
> @@ -51,15 +51,15 @@ int dev_dax_kmem_probe(struct device *dev)
>  		return -EINVAL;
>  	}
>  
> -	new_res_name = kstrdup(dev_name(dev), GFP_KERNEL);
> -	if (!new_res_name)
> +	res_name = kstrdup(dev_name(dev), GFP_KERNEL);
> +	if (!res_name)
>  		return -ENOMEM;
>  
>  	/* Region is permanently reserved if hotremove fails. */
> -	new_res = request_mem_region(range.start, range_len(&range), new_res_name);
> +	new_res = request_mem_region(range.start, range_len(&range), res_name);
>  	if (!new_res) {
>  		dev_warn(dev, "could not reserve region [%#llx-%#llx]\n", range.start, range.end);
> -		kfree(new_res_name);
> +		kfree(res_name);
>  		return -EBUSY;
>  	}
>  
> @@ -80,9 +80,11 @@ int dev_dax_kmem_probe(struct device *dev)
>  	if (rc) {
>  		release_resource(new_res);
>  		kfree(new_res);
> -		kfree(new_res_name);
> +		kfree(res_name);
>  		return rc;
>  	}
> +
> +	dev_set_drvdata(dev, res_name);
>  	dev_dax->dax_kmem_res = new_res;
>  
>  	return 0;
> @@ -94,7 +96,7 @@ 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 = res->name;
> +	const char *res_name = dev_get_drvdata(dev);

... because here you're back to "const".

>  	int rc;
>  
>  	/*
> 

I do wonder if it wouldn't all be easier to just have some

struct {
	const char *res_name;
	struct resource *res;
};

allocating that and storing it as drvdata. But let's see what the next
patch brings :)

-- 
Thanks,

David / dhildenb