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

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Date:   Thu, 16 Jul 2020 09:00:47 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Joao Martins <joao.m.martins@...cle.com>
Cc:     linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 22/22] device-dax: Introduce 'mapping' devices

On Thu, Jul 16, 2020 at 6:19 AM Joao Martins <joao.m.martins@...cle.com> wrote:
>
> 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.

Whoops, yes. Needs a unit test.