linux-kernel - [PATCH] dm raid: Remove unnecessary negation of a shift in raid10_format_to_md

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Date:   Thu, 24 Oct 2019 13:28:03 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...hat.com>
Cc:     dm-devel@...hat.com, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] dm raid: Remove unnecessary negation of a shift in raid10_format_to_md_layout

When building with Clang + -Wtautological-constant-compare:

 drivers/md/dm-raid.c:619:8: warning: converting the result of '<<' to a
 boolean always evaluates to true [-Wtautological-constant-compare]
                 r = !RAID10_OFFSET;
                      ^
 drivers/md/dm-raid.c:517:28: note: expanded from macro 'RAID10_OFFSET'
 #define RAID10_OFFSET                   (1 << 16) /* stripes with data
 copies area adjacent on devices */
                                           ^
 1 warning generated.

Negating a non-zero number will always make it zero, which is the
default value of r in this function so this statement is unnecessary;
remove it so that clang no longer warns.

Link: https://github.com/ClangBuiltLinux/linux/issues/753
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 drivers/md/dm-raid.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index b0aa595e4375..13fabc6779e5 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -616,7 +616,6 @@ static int raid10_format_to_md_layout(struct raid_set *rs,
 
 	} else if (algorithm == ALGORITHM_RAID10_FAR) {
 		f = copies;
-		r = !RAID10_OFFSET;
 		if (!test_bit(__CTR_FLAG_RAID10_USE_NEAR_SETS, &rs->ctr_flags))
 			r |= RAID10_USE_FAR_SETS;
 
-- 
2.24.0.rc1