linux-kernel - [PATCH] x86: kernel: fix unused variable warning in vm86

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Date:   Mon, 13 Feb 2017 15:05:11 +0900
From:   Seunghun Han <kkamagui@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Seunghun Han <kkamagui@...il.com>
Subject: [PATCH] x86: kernel: fix unused variable warning in vm86_32.c

If CONFIG_TRANSPARENT_HUGEPAGE is not set in kernel config, a warning is shown
in vm86_32.c.

The warning is as follows:
>arch/x86/kernel/vm86_32.c: In function ‘mark_screen_rdonly’:
>arch/x86/kernel/vm86_32.c:180:26: warning: unused variable ‘vma’ [-Wunused-variable]
> struct vm_area_struct *vma = find_vma(mm, 0xA0000);

The vma variable is used to call split_huge_pmd() macro function, but
split_huge_pmd() is defined as a null macro when CONFIG_TRANSPARENT_HUGEPAGE is
not set in kernel config. Therefore, the compiler shows an unused variable
warning.

To remove this warning, I change the split_huge_pmd() macro function to static
inline function and static inline null function.
Inline function works like a macro function, therefore there is no impact on
Linux kernel working.

Signed-off-by: Seunghun Han <kkamagui@...il.com>
---
 include/linux/huge_mm.h | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a3762d4..912a763 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -123,15 +123,12 @@ void deferred_split_huge_page(struct page *page);
 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long address, bool freeze, struct page *page);
 
-#define split_huge_pmd(__vma, __pmd, __address)				\
-	do {								\
-		pmd_t *____pmd = (__pmd);				\
-		if (pmd_trans_huge(*____pmd)				\
-					|| pmd_devmap(*____pmd))	\
-			__split_huge_pmd(__vma, __pmd, __address,	\
-						false, NULL);		\
-	}  while (0)
-
+static inline void split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+		unsigned long address)
+{
+	if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))
+		__split_huge_pmd(vma, pmd, address, false, NULL);
+}
 
 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
 		bool freeze, struct page *page);
@@ -241,9 +238,8 @@ static inline int split_huge_page(struct page *page)
 	return 0;
 }
 static inline void deferred_split_huge_page(struct page *page) {}
-#define split_huge_pmd(__vma, __pmd, __address)	\
-	do { } while (0)
-
+static inline void split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+		unsigned long address) {}
 static inline void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long address, bool freeze, struct page *page) {}
 static inline void split_huge_pmd_address(struct vm_area_struct *vma,
-- 
2.1.4