mm: Generalize HUGETLB_PAGE_SIZE_VARIABLE

HUGETLB_PAGE_SIZE_VARIABLE need not be defined for each individual
platform subscribing it. Instead just make it generic.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

arch/ia64/Kconfig

@@ -33,6 +33,7 @@ config IA64
 	select TTY
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_VIRT_CPU_ACCOUNTING
+	select HUGETLB_PAGE_SIZE_VARIABLE
 	select VIRT_TO_BUS
 	select GENERIC_IRQ_PROBE
 	select GENERIC_PENDING_IRQ if SMP
@@ -83,11 +84,6 @@ config STACKTRACE_SUPPORT
 config GENERIC_LOCKBREAK
 	def_bool n
 
-config HUGETLB_PAGE_SIZE_VARIABLE
-	bool
-	depends on HUGETLB_PAGE
-	default y
-
 config GENERIC_CALIBRATE_DELAY
 	bool
 	default y

arch/powerpc/Kconfig

@@ -232,6 +232,7 @@ config PPC
 	select HAVE_HARDLOCKUP_DETECTOR_PERF	if PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !HAVE_HARDLOCKUP_DETECTOR_ARCH
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
+	select HUGETLB_PAGE_SIZE_VARIABLE	if PPC_BOOK3S_64
 	select MMU_GATHER_RCU_TABLE_FREE
 	select MMU_GATHER_PAGE_SIZE
 	select HAVE_REGS_AND_STACK_ACCESS_API
@@ -416,11 +417,6 @@ config HIGHMEM
 
 source "kernel/Kconfig.hz"
 
-config HUGETLB_PAGE_SIZE_VARIABLE
-	bool
-	depends on HUGETLB_PAGE && PPC_BOOK3S_64
-	default y
-
 config MATH_EMULATION
 	bool "Math emulation"
 	depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE

mm/Kconfig

@@ -274,6 +274,14 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
 config ARCH_ENABLE_THP_MIGRATION
 	bool
 
+config HUGETLB_PAGE_SIZE_VARIABLE
+	def_bool n
+	depends on HUGETLB_PAGE
+	help
+	  When there are multiple HugeTLB sizes available on a platform
+	  and pageblock_order could then be a dynamic value instead of
+	  standard HUGETLB_PAGE_ORDER.
+
 config CONTIG_ALLOC
 	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA