linux-kernel - Re: [RFC PATCH] dax: add badblocks check to Device DAX

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Date:   Wed, 3 May 2017 23:25:38 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     "dan.j.williams@...el.com" <dan.j.williams@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dave.jiang@...el.com" <dave.jiang@...el.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: [RFC PATCH] dax: add badblocks check to Device DAX

On Wed, 2017-05-03 at 16:08 -0700, Dan Williams wrote:
> On Wed, May 3, 2017 at 3:51 PM, Dan Williams <dan.j.williams@...el.co
> m> wrote:
> > On Wed, May 3, 2017 at 3:41 PM, Kani, Toshimitsu <toshi.kani@....co
> > m> wrote:
> > > On Wed, 2017-05-03 at 14:48 -0700, Dan Williams wrote:
 :
> > 
> > I believe we already have all the data needed to calculate the data
> > offset. Given the following sysfs path:
> > 
> >     /sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0012:00/ndbus0/region1
> > /dax1.1/dax/dax1.0
> > 
> > ...we can find the associated namespace device from that dax1.1.
> > From
> > there we have the base address of the namespace and the size
> > device-dax instance.
> > 
> >     device_dax_data_offset == namespace_base + namespace_size -
> > device_dax_size
> 
> Dave reminds me that we do have the data offset of the device-dax
> instance at the libnvdimm level:
> 
>     /sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0012:00/ndbus0/region1/d
> ax1.1/resource
> 
> ...in this example, which maps to ndctl_dax_get_resource().

Thanks for the info!  I noticed why I did not catch this info before.

# ll /dev/dax*
crw------- 1 root root 251, 3 May  3 04:28 /dev/dax0.0

# pwd
/sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0012:00/ndbus0/region0/dax0.0

# grep . *
align:2097152
devtype:nd_dax
modalias:nd:t7
mode:none
numa_node:0
grep: power: Is a directory
grep: resource: No such device or address
grep: size: No such device or address
grep: subsystem: Is a directory
uevent:DEVTYPE=nd_dax
uevent:MODALIAS=nd:t7

But I noticed that "resource" and "size" that are under
".../region0/dax0.1" work.  Is this intended?

-Toshi