[PATCH v4 1/2] mm: hugetlb_vmemmap: introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP

[Muchun Song]

The feature of minimizing overhead of struct page associated with each
HugeTLB page is implemented on x86_64, however, the infrastructure of
this feature is already there, we could easily enable it for other
architectures.  Introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP for other
architectures to be easily enabled.  Just select this config if they
want to enable this feature.

Suggested-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Muchun Song <songmuchun at bytedance.com>
---
 arch/x86/Kconfig |  1 +
 fs/Kconfig       | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9f5bd41bf660..e69d42528542 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -119,6 +119,7 @@ config X86
 	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_HUGE_PMD_SHARE
+	select ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP	if X86_64
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_THP_SWAP		if X86_64
 	select ARCH_HAS_PARANOID_L1D_FLUSH
diff --git a/fs/Kconfig b/fs/Kconfig
index 6c7dc1387beb..f6db2af33738 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -245,9 +245,17 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
+#
+# Select this config option from the architecture Kconfig, if it is preferred
+# to enable the feature of minimizing overhead of struct page associated with
+# each HugeTLB page.
+#
+config ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
+	bool
+
 config HUGETLB_PAGE_FREE_VMEMMAP
 	def_bool HUGETLB_PAGE
-	depends on X86_64
+	depends on ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
 	depends on SPARSEMEM_VMEMMAP
 
 config HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON
-- 
2.11.0