[PATCH V3] mm: Generalize HUGETLB_PAGE_SIZE_VARIABLE

[Anshuman Khandual]

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

Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Christophe Leroy <christophe.leroy at csgroup.eu>
Cc: linux-ia64 at vger.kernel.org
Cc: linuxppc-dev at lists.ozlabs.org
Cc: linux-mm at kvack.org
Cc: linux-kernel at vger.kernel.org
Suggested-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.com>
---
This change was originally suggested in an earilier discussion. This
applies on v5.12-rc1 and has been build tested on all applicable
platforms i.e ia64 and powerpc.

https://patchwork.kernel.org/project/linux-mm/patch/1613024531-19040-3-git-send-email-anshuman.khandual@arm.com/

Changes in V3:

- Dropped the bool desciption that enabled user selection
- Dropped the dependency on HUGETLB_PAGE for HUGETLB_PAGE_SIZE_VARIABLE

Changes in V2:

https://patchwork.kernel.org/project/linux-mm/patch/1614661987-23881-1-git-send-email-anshuman.khandual@arm.com/

- Added a description for HUGETLB_PAGE_SIZE_VARIABLE
- Added HUGETLB_PAGE dependency while selecting HUGETLB_PAGE_SIZE_VARIABLE

Changes in V1:

https://patchwork.kernel.org/project/linux-mm/patch/1614577853-7452-1-git-send-email-anshuman.khandual@arm.com/

 arch/ia64/Kconfig    | 6 +-----
 arch/powerpc/Kconfig | 6 +-----
 mm/Kconfig           | 7 +++++++
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 2ad7a8d29fcc..dccf5bfebf48 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -32,6 +32,7 @@ config IA64
 	select TTY
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_VIRT_CPU_ACCOUNTING
+	select HUGETLB_PAGE_SIZE_VARIABLE if HUGETLB_PAGE
 	select VIRT_TO_BUS
 	select GENERIC_IRQ_PROBE
 	select GENERIC_PENDING_IRQ if SMP
@@ -82,11 +83,6 @@ 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
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 386ae12d8523..11fea95a1f2c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -231,6 +231,7 @@ 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 && HUGETLB_PAGE
 	select MMU_GATHER_RCU_TABLE_FREE
 	select MMU_GATHER_PAGE_SIZE
 	select HAVE_REGS_AND_STACK_ACCESS_API
@@ -415,11 +416,6 @@ 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
diff --git a/mm/Kconfig b/mm/Kconfig
index 24c045b24b95..4413a69e7850 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -274,6 +274,13 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
 config ARCH_ENABLE_THP_MIGRATION
 	bool
 
+config HUGETLB_PAGE_SIZE_VARIABLE
+	def_bool n
+	help
+	  Allows the pageblock_order value to be dynamic instead of just standard
+	  HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
+	  on a platform.
+
 config CONTIG_ALLOC
 	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 
-- 
2.20.1