[PATCHv2 0/3] mm: bugfix for NULL reference in mm on all archs

[Pingfan Liu]

This bug is original reported at https://lore.kernel.org/patchwork/patch/1020838/
In a short word, this bug should affect all archs, where a machine with a
numa-node having no memory, if nr_cpus prevents the instance of nodeA, and the
device on nodeA tries to allocate memory with device->numa_node info.
And node_zonelist(preferred_nid, gfp_mask) will panic due to uninstanced nodeA.

And there are two alternative methods to fix it.
-1st. Fix it in mm system
-2nd. Fix it in all archs independently, by online all possible nodes.

Originaly, I tries to fix it by the 1st method, while Michal suggests the 2nd one.
This series [1-2/3] tries to resolve some defect in v1, pointed out by Michal.
For discussion purpose, I send [3/3] in this thread, which tries to show e.g of
the 2nd method on powerpc platform.
For x86, I still help Michal to verify his patch on my test machine, please see:
https://lore.kernel.org/patchwork/comment/1208479/
https://lore.kernel.org/patchwork/comment/1210452/

It has already cost a little long time to find a solution, cc x86 and ppc mailing list
and hope their maintainers to give some suggestion to speed up the final solution.

Pingfan Liu (3):
  mm/numa: change the topo of build_zonelist_xx()
  mm/numa: build zonelist when alloc for device on offline node
  powerpc/numa: make all possible node be instanced against NULL
    reference in node_zonelist()

 arch/powerpc/mm/numa.c | 13 ++++++--
 include/linux/gfp.h    | 10 +++++-
 mm/page_alloc.c        | 85 ++++++++++++++++++++++++++++++++++++--------------
 3 files changed, 81 insertions(+), 27 deletions(-)

Cc: linuxppc-dev at lists.ozlabs.org
Cc: x86 at kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Michal Hocko <mhocko at suse.com>
Cc: Vlastimil Babka <vbabka at suse.cz>
Cc: Mike Rapoport <rppt at linux.vnet.ibm.com>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: Jonathan Cameron <Jonathan.Cameron at huawei.com>
Cc: David Rientjes <rientjes at google.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Borislav Petkov <bp at alien8.de>
Cc: "H. Peter Anvin" <hpa at zytor.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
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2.7.4