powerpc/mm: Update FORCE_MAX_ZONEORDER range to allow hugetlb w/4K

For hugetlb to work with 4K page size, we need MAX_ORDER to be 13 or
more. When switching from a 64K page size to 4K linux page size using
make oldconfig, we end up with a CONFIG_FORCE_MAX_ZONEORDER value of 9.
This results in a 16M hugepage beiing considered as a gigantic huge page
which in turn results in failure to setup hugepages if gigantic hugepage
support is not enabled.

This also results in kernel crash with 4K radix configuration. We
hit the below BUG_ON on radix:

  kernel BUG at mm/huge_memory.c:364!
  Oops: Exception in kernel mode, sig: 5 [#1]
  SMP NR_CPUS=2048 NUMA PowerNV
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc1-00006-gbae9cc6 #1
  task: c0000000f1af8000 task.stack: c0000000f1aec000
  NIP: c000000000c5fa0c LR: c000000000c5f9d8 CTR: c000000000c5f9a4
  REGS: c0000000f1aef920 TRAP: 0700   Not tainted (4.8.0-rc1-00006-gbae9cc6)
  MSR: 9000000102029033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE,TM[E]>  CR: 24000844  XER: 00000000
  CFAR: c000000000c5f9e0 SOFTE: 1
  ....
  NIP [c000000000c5fa0c] hugepage_init+0x68/0x238
  LR [c000000000c5f9d8] hugepage_init+0x34/0x238

Fixes: a7ee539584acf ("powerpc/Kconfig: Update config option based on page size")
Cc: stable@vger.kernel.org # v4.7+
Reported-by: Santhosh <santhog4@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9416e35f15b2741d1329ea202dbaf739f901cc48..0a70c86855d9fb0b7b44d3a968009110dfd2665e 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -632,7 +632,7 @@ config FORCE_MAX_ZONEORDER
        int "Maximum zone order"
        range 8 9 if PPC64 && PPC_64K_PAGES
        default "9" if PPC64 && PPC_64K_PAGES
-       range 9 13 if PPC64 && !PPC_64K_PAGES
+       range 13 13 if PPC64 && !PPC_64K_PAGES
        default "13" if PPC64 && !PPC_64K_PAGES
        range 9 64 if PPC32 && PPC_16K_PAGES
        default "9" if PPC32 && PPC_16K_PAGES