linux-kernel - [PATCH AUTOSEL 4.9 013/114] arm64: Fix compiler warning from pte

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Date:   Wed, 22 May 2019 15:28:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Qian Cai <cai@....pw>, Will Deacon <will.deacon@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.9 013/114] arm64: Fix compiler warning from pte_unmap() with -Wunused-but-set-variable

From: Qian Cai <cai@....pw>

[ Upstream commit 74dd022f9e6260c3b5b8d15901d27ebcc5f21eda ]

When building with -Wunused-but-set-variable, the compiler shouts about
a number of pte_unmap() users, since this expands to an empty macro on
arm64:

  | mm/gup.c: In function 'gup_pte_range':
  | mm/gup.c:1727:16: warning: variable 'ptem' set but not used
  | [-Wunused-but-set-variable]
  | mm/gup.c: At top level:
  | mm/memory.c: In function 'copy_pte_range':
  | mm/memory.c:821:24: warning: variable 'orig_dst_pte' set but not used
  | [-Wunused-but-set-variable]
  | mm/memory.c:821:9: warning: variable 'orig_src_pte' set but not used
  | [-Wunused-but-set-variable]
  | mm/swap_state.c: In function 'swap_ra_info':
  | mm/swap_state.c:641:15: warning: variable 'orig_pte' set but not used
  | [-Wunused-but-set-variable]
  | mm/madvise.c: In function 'madvise_free_pte_range':
  | mm/madvise.c:318:9: warning: variable 'orig_pte' set but not used
  | [-Wunused-but-set-variable]

Rewrite pte_unmap() as a static inline function, which silences the
warnings.

Signed-off-by: Qian Cai <cai@....pw>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/include/asm/pgtable.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 3a30a3994e4a2..73e3718356b05 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -413,6 +413,8 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)
 	return pmd_val(pmd) & PHYS_MASK & (s32)PAGE_MASK;
 }
 
+static inline void pte_unmap(pte_t *pte) { }
+
 /* Find an entry in the third-level page table. */
 #define pte_index(addr)		(((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
 
@@ -421,7 +423,6 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)
 
 #define pte_offset_map(dir,addr)	pte_offset_kernel((dir), (addr))
 #define pte_offset_map_nested(dir,addr)	pte_offset_kernel((dir), (addr))
-#define pte_unmap(pte)			do { } while (0)
 #define pte_unmap_nested(pte)		do { } while (0)
 
 #define pte_set_fixmap(addr)		((pte_t *)set_fixmap_offset(FIX_PTE, addr))
-- 
2.20.1