linux-kernel - [PATCH] [4.8-rc7, regression] fault_in_multipages

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Date:   Mon, 26 Sep 2016 09:57:33 +1000
From:   Dave Chinner <david@...morbit.com>
To:     linux-kernel@...r.kernel.org
Cc:     viro@...iv.linux.org.uk, torvalds@...ux-foundation.org
Subject: [PATCH] [4.8-rc7, regression] fault_in_multipages_readable() throws set-but-unused error

From: Dave Chinner <dchinner@...hat.com>

When building XFS with -Werror, it now fails with:

./include/linux/pagemap.h: In function ¿fault_in_multipages_readable¿:
./include/linux/pagemap.h:602:16: error: variable ¿c¿ set but not used [-Werror=unused-but-set-variable]
  volatile char c;
                ^

This is a regression caused by commit e23d415 ("fix
fault_in_multipages_...() on architectures with no-op access_ok()").
Fix it by re-adding the "(void)c" trick taht was previously used to
make the compiler think the variable is used.

Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
 include/linux/pagemap.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7e3d537..01e8443 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -620,6 +620,7 @@ static inline int fault_in_multipages_readable(const char __user *uaddr,
 		return __get_user(c, end);
 	}
 
+	(void)c;
 	return 0;
 }
 
-- 
2.8.0.rc3