[PATCH 1/3] mm: generalize VM_BUG_ON() macros

[Kirill A. Shutemov]

This patch makes VM_BUG_ON() to accept one to three arguments after the
condition. Any of these arguments can be page, vma or mm. VM_BUG_ON()
will dump info about the argument using appropriate dump_* function.

It's intended to replace separate VM_BUG_ON_PAGE(), VM_BUG_ON_VMA(),
VM_BUG_ON_MM() and allows additional use-cases like:

  VM_BUG_ON(cond, vma, page);
  VM_BUG_ON(cond, vma, src_page, dst_page);
  VM_BUG_ON(cond, mm, src_vma, dst_vma);
  ...

It's possible to extend list of supported data-structures or number of
arguments VM_BUG_ON() can accept.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/mmdebug.h | 49 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 877ef226f90f..12f304a36b01 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -14,33 +14,60 @@ void dump_vma(const struct vm_area_struct *vma);
 void dump_mm(const struct mm_struct *mm);
 
 #ifdef CONFIG_DEBUG_VM
-#define VM_BUG_ON(cond) BUG_ON(cond)
-#define VM_BUG_ON_PAGE(cond, page)					\
+#define GET_MACRO(_1, _2, _3, _4, NAME, ...) NAME
+
+#define _VM_DUMP(arg, cond) do {					\
+	if (__builtin_types_compatible_p(typeof(*arg), struct page))	\
+		dump_page((struct page *) arg,				\
+				"VM_BUG_ON(" __stringify(cond)")");	\
+	else if (__builtin_types_compatible_p(typeof(*arg),		\
+				struct vm_area_struct))			\
+		dump_vma((struct vm_area_struct *) arg);		\
+	else if (__builtin_types_compatible_p(typeof(*arg),		\
+				struct mm_struct))			\
+		dump_mm((struct mm_struct *) arg);			\
+	else								\
+		BUILD_BUG();						\
+} while(0)
+
+#define _VM_BUG_ON_ARG1(cond, arg1)					\
 	do {								\
 		if (unlikely(cond)) {					\
-			dump_page(page, "VM_BUG_ON_PAGE(" __stringify(cond)")");\
+			_VM_DUMP(arg1, cond);				\
 			BUG();						\
 		}							\
-	} while (0)
-#define VM_BUG_ON_VMA(cond, vma)					\
+	} while(0)
+#define _VM_BUG_ON_ARG2(cond, arg1, arg2)				\
 	do {								\
 		if (unlikely(cond)) {					\
-			dump_vma(vma);					\
+			_VM_DUMP(arg1, cond);				\
+			_VM_DUMP(arg2, cond);				\
 			BUG();						\
 		}							\
-	} while (0)
-#define VM_BUG_ON_MM(cond, mm)						\
+	} while(0)
+#define _VM_BUG_ON_ARG3(cond, arg1, arg2, arg3)				\
 	do {								\
 		if (unlikely(cond)) {					\
-			dump_mm(mm);					\
+			_VM_DUMP(arg1, cond);				\
+			_VM_DUMP(arg2, cond);				\
+			_VM_DUMP(arg3, cond);				\
 			BUG();						\
 		}							\
-	} while (0)
+	} while(0)
+
+#define VM_BUG_ON(...) GET_MACRO(__VA_ARGS__,				\
+		_VM_BUG_ON_ARG3,					\
+		_VM_BUG_ON_ARG2,					\
+		_VM_BUG_ON_ARG1,					\
+		BUG_ON)(__VA_ARGS__)
+#define VM_BUG_ON_PAGE VM_BUG_ON
+#define VM_BUG_ON_VMA VM_BUG_ON
+#define VM_BUG_ON_MM VM_BUG_ON
 #define VM_WARN_ON(cond) WARN_ON(cond)
 #define VM_WARN_ON_ONCE(cond) WARN_ON_ONCE(cond)
 #define VM_WARN_ONCE(cond, format...) WARN_ONCE(cond, format)
 #else
-#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
+#define VM_BUG_ON(cond, ...) BUILD_BUG_ON_INVALID(cond)
 #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
 #define VM_BUG_ON_VMA(cond, vma) VM_BUG_ON(cond)
 #define VM_BUG_ON_MM(cond, mm) VM_BUG_ON(cond)
-- 
2.1.0

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