linux-kernel - RE: [PATCH 5/5] mm/hotplug: export try_online

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Message-ID: <068d01d524e2$aa6f3000$ff4d9000$@d-silva.org>
Date:   Mon, 17 Jun 2019 18:00:00 +1000
From:   "Alastair D'Silva" <alastair@...ilva.org>
To:     "'Christoph Hellwig'" <hch@...radead.org>
Cc:     "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>,
        "'David Hildenbrand'" <david@...hat.com>,
        "'Oscar Salvador'" <osalvador@...e.com>,
        "'Michal Hocko'" <mhocko@...e.com>,
        "'Pavel Tatashin'" <pasha.tatashin@...een.com>,
        "'Wei Yang'" <richard.weiyang@...il.com>,
        "'Arun KS'" <arunks@...eaurora.org>, "'Qian Cai'" <cai@....pw>,
        "'Thomas Gleixner'" <tglx@...utronix.de>,
        "'Ingo Molnar'" <mingo@...nel.org>,
        "'Josh Poimboeuf'" <jpoimboe@...hat.com>,
        "'Jiri Kosina'" <jkosina@...e.cz>,
        "'Mukesh Ojha'" <mojha@...eaurora.org>,
        "'Mike Rapoport'" <rppt@...ux.vnet.ibm.com>,
        "'Baoquan He'" <bhe@...hat.com>,
        "'Logan Gunthorpe'" <logang@...tatee.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linux-nvdimm@...ts.01.org>
Subject: RE: [PATCH 5/5] mm/hotplug: export try_online_node

> -----Original Message-----
> From: Christoph Hellwig <hch@...radead.org>
> Sent: Monday, 17 June 2019 5:15 PM
> To: Alastair D'Silva <alastair@...ilva.org>
> Cc: Peter Zijlstra <peterz@...radead.org>; Andrew Morton <akpm@...ux-
> foundation.org>; David Hildenbrand <david@...hat.com>; Oscar Salvador
> <osalvador@...e.com>; Michal Hocko <mhocko@...e.com>; Pavel Tatashin
> <pasha.tatashin@...een.com>; Wei Yang <richard.weiyang@...il.com>;
> Arun KS <arunks@...eaurora.org>; Qian Cai <cai@....pw>; Thomas Gleixner
> <tglx@...utronix.de>; Ingo Molnar <mingo@...nel.org>; Josh Poimboeuf
> <jpoimboe@...hat.com>; Jiri Kosina <jkosina@...e.cz>; Mukesh Ojha
> <mojha@...eaurora.org>; Mike Rapoport <rppt@...ux.vnet.ibm.com>;
> Baoquan He <bhe@...hat.com>; Logan Gunthorpe
> <logang@...tatee.com>; linux-mm@...ck.org; linux-
> kernel@...r.kernel.org; linux-nvdimm@...ts.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@...ilva.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@...ilva.org
blog: http://alastair.d-silva.org    Twitter: @EvilDeece