linux-kernel - Re: [PATCH v2 15/17] libnvdimm: Set numa

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Date:	Thu, 25 Jun 2015 18:55:15 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	"Williams, Dan J" <dan.j.williams@...el.com>
Cc:	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"hch@....de" <hch@....de>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"axboe@...nel.dk" <axboe@...nel.dk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2 15/17] libnvdimm: Set numa_node to NVDIMM devices

On Thu, 2015-06-25 at 23:42 +0000, Williams, Dan J wrote:
> On Thu, 2015-06-25 at 16:55 -0600, Toshi Kani wrote:
> > On Thu, 2015-06-25 at 15:34 -0700, Dan Williams wrote:
> > > On Thu, Jun 25, 2015 at 3:11 PM, Toshi Kani <toshi.kani@...com> wrote:
> > > > On Thu, 2015-06-25 at 15:00 -0700, Dan Williams wrote:
> > > > Yes, I see no problem with bound BTTs and their device files.  So, how
> > > > do we bind BTT with this new version?
> > > >
> > > 
> > > # cd /sys/bus/nd/devices
> > > # uuidgen > btt6/uuid
> > > # echo 4096 > btt6/sector_size
> > > # echo namespace6.0 > btt6/namespace
> > > # echo namespace6.0 > ../drivers/nd_pmem/unbind
> > > # echo btt6 > ../drivers/nd_pmem/bind
> > > 
> > > After reboot, when the system sees namespace6.0 again it will notice
> > > the btt instance and attach bttX instead.  The net effect is that now
> > > you'll only ever have /dev/pmem6 or /dev/pmem6s, never both at the
> > > same time that was a side effect of the stacking approach.
> > > 
> > > I'll post the patch that updates libndctl and the unit tests shortly
> > 
> > Maybe I am missing something, but I am getting errors on my system.  (I
> > used btt0 since there is no btt6.)
> > 
> > # cat bind.sh
> > set -x
> > cd /sys/bus/nd/devices
> > uuidgen > btt0/uuid
> > echo 4096 > btt0/sector_size
> > echo namespace0.0 > btt0/namespace
> > echo namespace0.0 > ../drivers/nd_pmem/unbind
> > echo btt0 > ../drivers/nd_pmem/bind
> > 
> > # sh bind.sh
> > + cd /sys/bus/nd/devices
> > + uuidgen
> > + echo 4096
> > + echo namespace0.0
> > bind.sh: line 6: echo: write error: Device or resource busy
> > + echo namespace0.0
> > bind.sh: line 7: echo: write error: No such device
> > + echo btt0
> > bind.sh: line 8: echo: write error: No such device
> > 
> > # dmesg
> >  :
> > [12513.839162] nd btt0: uuid_store: result: 0 wrote:
> > b32cd195-9aae-4c54-a5ac-49adb50a8a98
> > [12513.880286] nd btt0: sector_size_store: result: 0 wrote: 4096
> > [12513.909494] nd btt0: namespace0.0 already claimed
> > [12513.933364] nd btt0: namespace_store: result: -16 wrote: namespace0.0
> > [12513.966808]  ndbus0: nd_pmem.probe(btt0) = -19
> > 
> 
> So this turned out to be a perfect example of why we might want to have
> the region-id in the btt device name just like namespaces, because btt0
> was actually bound to namespace4.0 on Toshi's system.  The following
> update, that I will fold in to the series, fixes this.  Note that the
> association of btt id to to namespace is still non-deterministic.  I.e.
> btt0.1 could be assigned as the btt for namespace0.0, but at least when
> looking at /sys/bus/nd/devices it will be clear which btts belong to
> which regions.
> 
> # ls /sys/bus/nd/devices
> btt0.0  btt3.0  btt6.0        namespace2.0  namespace5.0  nmem1  nmem4    region2  region5
> btt1.0  btt4.0  namespace0.0  namespace3.0  namespace6.0  nmem2  region0  region3  region6
> btt2.0  btt5.0  namespace1.0  namespace4.0  nmem0         nmem3  region1  region4

Yes, this works nicely. :-)

Now, how do I unbind BTT?  I did the following as a guess, but BTT got
reattached again before I have a chance to delete the metadata, which I
need /dev/pmemN.  

NUM=1 
cd /sys/bus/nd/devices
echo ""  > btt${NUM}.1/namespace
echo btt${NUM}.1 > ../drivers/nd_pmem/unbind
echo namespace${NUM}.0 > ../drivers/nd_pmem/bind

Thanks,
-Toshi



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