mm/hugetlb: introduce ARCH_HAS_GIGANTIC_PAGE

Avoid making ifdef get pretty unwieldy if many ARCHs support gigantic
page.  No functional change with this patch.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Yisheng Xie <[email protected]>
Suggested-by: Michal Hocko <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Naoya Horiguchi <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: Hanjun Guo <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Sudeep Holla <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Mike Kravetz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Yisheng Xie

arch/s390/Kconfig

@@ -71,6 +71,7 @@ config S390
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_UBSAN_SANITIZE_ALL

arch/x86/Kconfig

@@ -28,6 +28,7 @@ config X86
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_GIGANTIC_PAGE		if X86_64
 	select ARCH_HAS_KCOV			if X86_64
 	select ARCH_HAS_PMEM_API		if X86_64
 	select ARCH_HAS_MMIO_FLUSH

fs/Kconfig

@@ -200,6 +200,9 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
+config ARCH_HAS_GIGANTIC_PAGE
+	bool
+
 source "fs/configfs/Kconfig"
 source "fs/efivarfs/Kconfig"
 

mm/hugetlb.c

@@ -1022,7 +1022,7 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
 		((node = hstate_next_node_to_free(hs, mask)) || 1);	\
 		nr_nodes--)
 
-#if (defined(CONFIG_X86_64) || defined(CONFIG_S390)) && \
+#if defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) && \
 	((defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || \
 	defined(CONFIG_CMA))
 static void destroy_compound_gigantic_page(struct page *page,