Re: [PATCH 5/5] mm/hotplug: export try_online_node

Re: [PATCH 5/5] mm/hotplug: export try_online_node

[Christoph Hellwig]

On Mon, Jun 17, 2019 at 05:05:30PM +1000, Alastair D'Silva wrote:
> On Mon, 2019-06-17 at 08:59 +0200, Peter Zijlstra wrote:
> > On Mon, Jun 17, 2019 at 02:36:31PM +1000, Alastair D'Silva wrote:
> > > From: Alastair D'Silva <alastair@d-silva.org>
> > > 
> > > If an external driver module supplies physical memory and needs to
> > > expose
> > 
> > Why would you ever want to allow a module to do such a thing?
> > 
> 
> I'm working on a driver for Storage Class Memory, connected via an
> OpenCAPI link.
> 
> The memory is only usable once the card says it's OK to access it.

And all that should go through our pmem APIs, not not directly
poke into mm internals.  And if you still need core patches send them
along with the actual driver.

RE: [PATCH 5/5] mm/hotplug: export try_online_node

[Alastair D'Silva]

> -----Original Message-----
> From: Christoph Hellwig <hch@infradead.org>
> Sent: Monday, 17 June 2019 5:15 PM
> To: Alastair D'Silva <alastair@d-silva.org>
> Cc: Peter Zijlstra <peterz@infradead.org>; Andrew Morton <akpm@linux-
> foundation.org>; David Hildenbrand <david@redhat.com>; Oscar Salvador
> <osalvador@suse.com>; Michal Hocko <mhocko@suse.com>; Pavel Tatashin
> <pasha.tatashin@soleen.com>; Wei Yang <richard.weiyang@gmail.com>;
> Arun KS <arunks@codeaurora.org>; Qian Cai <cai@lca.pw>; Thomas Gleixner
> <tglx@linutronix.de>; Ingo Molnar <mingo@kernel.org>; Josh Poimboeuf
> <jpoimboe@redhat.com>; Jiri Kosina <jkosina@suse.cz>; Mukesh Ojha
> <mojha@codeaurora.org>; Mike Rapoport <rppt@linux.vnet.ibm.com>;
> Baoquan He <bhe@redhat.com>; Logan Gunthorpe
> <logang@deltatee.com>; linux-mm@kvack.org; linux-
> kernel@vger.kernel.org; linux-nvdimm@lists.01.org
> Subject: Re: [PATCH 5/5] mm/hotplug: export try_online_node
> 
> On Mon, Jun 17, 2019 at 05:05:30PM +1000, Alastair D'Silva wrote:
> > On Mon, 2019-06-17 at 08:59 +0200, Peter Zijlstra wrote:
> > > On Mon, Jun 17, 2019 at 02:36:31PM +1000, Alastair D'Silva wrote:
> > > > From: Alastair D'Silva <alastair@d-silva.org>
> > > >
> > > > If an external driver module supplies physical memory and needs to
> > > > expose
> > >
> > > Why would you ever want to allow a module to do such a thing?
> > >
> >
> > I'm working on a driver for Storage Class Memory, connected via an
> > OpenCAPI link.
> >
> > The memory is only usable once the card says it's OK to access it.
> 
> And all that should go through our pmem APIs, not not directly poke into
mm
> internals.  And if you still need core patches send them along with the
actual
> driver.

I tried that, but I was getting crashes as the NUMA data structures for that
node were not initialised.

Calling this was required to prevent uninitialized accesses in the pmem
library.

-- 
Alastair D'Silva           mob: 0423 762 819
skype: alastair_dsilva     msn: alastair@d-silva.org
blog: http://alastair.d-silva.org    Twitter: @EvilDeece



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Re: [PATCH 5/5] mm/hotplug: export try_online_node

['Christoph Hellwig']

On Mon, Jun 17, 2019 at 06:00:00PM +1000, Alastair D'Silva wrote:
> > And all that should go through our pmem APIs, not not directly poke into
> mm
> > internals.  And if you still need core patches send them along with the
> actual
> > driver.
> 
> I tried that, but I was getting crashes as the NUMA data structures for that
> node were not initialised.
> 
> Calling this was required to prevent uninitialized accesses in the pmem
> library.

Please send your driver to the linux-nvdimm and linux-mm lists so that
it can be carefully reviewed.