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From:   "Alastair D'Silva" <alastair@d-silva.org>
To:     "'Christoph Hellwig'" <hch@infradead.org>
Cc:     "'Peter Zijlstra'" <peterz@infradead.org>,
        "'Andrew Morton'" <akpm@linux-foundation.org>,
        "'David Hildenbrand'" <david@redhat.com>,
        "'Oscar Salvador'" <osalvador@suse.com>,
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        "'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>
References: <20190617043635.13201-1-alastair@au1.ibm.com> <20190617043635.13201-6-alastair@au1.ibm.com> <20190617065921.GV3436@hirez.programming.kicks-ass.net> <f1bad6f784efdd26508b858db46f0192a349c7a1.camel@d-silva.org> <20190617071527.GA14003@infradead.org>
In-Reply-To: <20190617071527.GA14003@infradead.org>
Subject: RE: [PATCH 5/5] mm/hotplug: export try_online_node
Date:   Mon, 17 Jun 2019 18:00:00 +1000
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> -----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