linux-kernel - [PATCH] s390/mm: Explicitly compare PAGE_DEFAULT_KEY against zero in storage_key_init

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Message-Id: <20200214064207.10381-1-natechancellor@gmail.com>
Date:   Thu, 13 Feb 2020 23:42:07 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] s390/mm: Explicitly compare PAGE_DEFAULT_KEY against zero in storage_key_init_range

Clang warns:

 In file included from ../arch/s390/purgatory/purgatory.c:10:
 In file included from ../include/linux/kexec.h:18:
 In file included from ../include/linux/crash_core.h:6:
 In file included from ../include/linux/elfcore.h:5:
 In file included from ../include/linux/user.h:1:
 In file included from ../arch/s390/include/asm/user.h:11:
 ../arch/s390/include/asm/page.h:45:6: warning: converting the result of
 '<<' to a boolean always evaluates to false
 [-Wtautological-constant-compare]
         if (PAGE_DEFAULT_KEY)
            ^
 ../arch/s390/include/asm/page.h:23:44: note: expanded from macro
 'PAGE_DEFAULT_KEY'
 #define PAGE_DEFAULT_KEY        (PAGE_DEFAULT_ACC << 4)
                                                  ^
 1 warning generated.

Explicitly compare this against zero to silence the warning as it is
intended to be used in a boolean context.

Fixes: de3fa841e429 ("s390/mm: fix compile for PAGE_DEFAULT_KEY != 0")
Link: https://github.com/ClangBuiltLinux/linux/issues/860
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 arch/s390/include/asm/page.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 85e944f04c70..1019efd85b9d 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -42,7 +42,7 @@ void __storage_key_init_range(unsigned long start, unsigned long end);
 
 static inline void storage_key_init_range(unsigned long start, unsigned long end)
 {
-	if (PAGE_DEFAULT_KEY)
+	if (PAGE_DEFAULT_KEY != 0)
 		__storage_key_init_range(start, end);
 }
 
-- 
2.25.0