linux-kernel - Re: [PATCH v2 22/22] device-dax: Introduce 'mapping' devices

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Message-ID: <7ecd1b82-06ab-be49-4b92-ac42caab146c@oracle.com>
Date:   Thu, 16 Jul 2020 14:18:49 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...ts.01.org, Vishal Verma <vishal.l.verma@...el.com>,
        peterz@...radead.org, dave.hansen@...ux.intel.com,
        ard.biesheuvel@...aro.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        hch@....de
Subject: Re: [PATCH v2 22/22] device-dax: Introduce 'mapping' devices

On 7/12/20 5:28 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.
> 
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/dax/bus.c         |  191 +++++++++++++++++++++++++++++++++++++++++++++
>  drivers/dax/dax-private.h |   14 +++
>  2 files changed, 203 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index f342e36c69a1..8b6c4ddc5f42 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -579,6 +579,167 @@ 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) {
            ^^^^^^^^^^^^^^^^^^^^^ it's 'mapping->range_id < 0'

Otherwise 'mapping0' sysfs entries won't work.
Disabled ranges use id -1.

	Joao