[PATCHv2, RESEND 18/19] mm: define default PGTABLE_LEVELS to two

[Kirill A. Shutemov]

By this time all architectures which support more than two page table
levels should be covered. This patch add default definiton of
PGTABLE_LEVELS equal 2.

We also add assert to detect inconsistence between CONFIG_PGTABLE_LEVELS
and __PAGETABLE_PMD_FOLDED/__PAGETABLE_PUD_FOLDED.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
 arch/Kconfig                  | 4 ++++
 include/asm-generic/pgtable.h | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 05d7a8a458d5..a9c95d36ba70 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -484,6 +484,10 @@ config HAVE_IRQ_EXIT_ON_IRQ_STACK
 	  This spares a stack switch and improves cache usage on softirq
 	  processing.
 
+config PGTABLE_LEVELS
+	int
+	default 2
+
 #
 # ABI hall of shame
 #
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 4d46085c1b90..1f9f5da6828f 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -7,6 +7,11 @@
 #include <linux/mm_types.h>
 #include <linux/bug.h>
 
+#if 4 - defined(__PAGETABLE_PUD_FOLDED) - defined(__PAGETABLE_PMD_FOLDED) != \
+	CONFIG_PGTABLE_LEVELS
+#error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{PUD,PMD}_FOLDED
+#endif
+
 /*
  * On almost all architectures and configurations, 0 can be used as the
  * upper ceiling to free_pgtables(): on many architectures it has the same
-- 
2.1.4

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