linux-kernel - [PATCH v5 01/14] mmdebug: Always evaluate the arguments to VM_BUG_ON

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Date:	Thu, 10 Mar 2016 18:55:18 -0500
From:	Matthew Wilcox <matthew.r.wilcox@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matthew Wilcox <matthew.r.wilcox@...el.com>, linux-mm@...ck.org,
	linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, willy@...ux.intel.com
Subject: [PATCH v5 01/14] mmdebug: Always evaluate the arguments to VM_BUG_ON_*

I recently got the order of arguments to VM_BUG_ON_VMA the wrong way
around, which was only noticable when compiling with CONFIG_DEBUG_VM.
Prevent the next mistake of this kind by making the macros evaluate both
their arguments at compile time (this has no effect on the built kernel).

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@...el.com>
---
 include/linux/mmdebug.h | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index de7be78..abfc316 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -41,9 +41,24 @@ void dump_mm(const struct mm_struct *mm);
 #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_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)
+#define VM_BUG_ON_PAGE(cond, page)					\
+	do {								\
+		if (0) dump_page(page, "");				\
+		VM_BUG_ON(cond);					\
+	} while (0)
+
+#define VM_BUG_ON_VMA(cond, vma)					\
+	do {								\
+		if (0) dump_vma(vma);					\
+		VM_BUG_ON(cond);					\
+	} while (0)
+
+#define VM_BUG_ON_MM(cond, mm)						\
+	do {								\
+		if (0) dump_mm(mm);					\
+		VM_BUG_ON(cond);					\
+	} while (0)
+
 #define VM_WARN_ON(cond) BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)
-- 
2.7.0