linux-kernel - Re: [PATCH 12/12] device-dax: Introduce 'mapping' devices

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Date:   Tue, 24 Mar 2020 16:27:44 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-mm@...ck.org, dave.hansen@...ux.intel.com, hch@....de,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/12] device-dax: Introduce 'mapping' devices

On 3/23/20 11:55 PM, Dan Williams wrote:
> In support of interrogating the physical address layout of a device with
> dis-contiguous ranges, introduce a sysfs directory with 'start', 'end',
> and 'page_offset' attributes. The alternative is trying to parse
> /proc/iomem, and that file will not reflect the extent layout until the
> device is enabled.
> 
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/dax/bus.c         |  190 +++++++++++++++++++++++++++++++++++++++++++++
>  drivers/dax/dax-private.h |   14 +++
>  2 files changed, 202 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 07aeb8fa9ee8..645449a079bd 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -558,6 +558,167 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
>  }
>  EXPORT_SYMBOL_GPL(alloc_dax_region);
>  
> +static void dax_mapping_release(struct device *dev)
> +{
> +	struct dax_mapping *mapping = to_dax_mapping(dev);
> +	struct dev_dax *dev_dax = to_dev_dax(dev->parent);
> +
> +	ida_free(&dev_dax->ida, mapping->id);
> +	kfree(mapping);
> +}
> +
> +static void unregister_dax_mapping(void *data)
> +{
> +	struct device *dev = data;
> +	struct dax_mapping *mapping = to_dax_mapping(dev);
> +	struct dev_dax *dev_dax = to_dev_dax(dev->parent);
> +	struct dax_region *dax_region = dev_dax->region;
> +
> +	dev_dbg(dev, "%s\n", __func__);
> +
> +	device_lock_assert(dax_region->dev);
> +
> +	dev_dax->ranges[mapping->range_id].mapping = NULL;
> +	mapping->range_id = -1;
> +
> +	device_del(dev);
> +	put_device(dev);
> +}
> +
> +static struct dev_dax_range *get_dax_range(struct device *dev)
> +{
> +	struct dax_mapping *mapping = to_dax_mapping(dev);
> +	struct dev_dax *dev_dax = to_dev_dax(dev->parent);
> +	struct dax_region *dax_region = dev_dax->region;
> +
> +	device_lock(dax_region->dev);
> +	if (mapping->range_id < 1) {
            ^^^^^^^^^^^^^^^^^^^^^ perhaps "mapping->range_id < 0" ?

AFAICT, invalid/disabled ranges have id to -1.

Otherwise we can't use mapping0 entry fields.

 Joao