linux-kernel - [PATCH] dm block manager: use do/while(0) for empty macros

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Date:   Tue, 25 Oct 2016 17:54:10 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Mike Snitzer <snitzer@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Alasdair Kergon <agk@...hat.com>,
        dm-devel@...hat.com, Shaohua Li <shli@...nel.org>,
        Mikulas Patocka <mpatocka@...hat.com>,
        Joe Thornber <ejt@...hat.com>, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] dm block manager: use do/while(0) for empty macros

make W=1 reports a new warning for the dm-block-manager:

drivers/md/persistent-data/dm-block-manager.c: In function ‘dm_bm_unlock’:
drivers/md/persistent-data/dm-block-manager.c:598:3: error: suggest braces around empty body in an ‘else’ statement [-Werror=empty-body]

This is completely harmless, but generally speaking it's a good idea to
address this warning as it can often detect nasty bugs, and replacing
empty macros with "do { } while (0)" is generally considered good style
to make code more robust anyway.

Fixes: f94bdb2e26b6 ("dm block manager: make block locking optional")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/md/persistent-data/dm-block-manager.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/md/persistent-data/dm-block-manager.c b/drivers/md/persistent-data/dm-block-manager.c
index b619c383d88d..a6dde7cab458 100644
--- a/drivers/md/persistent-data/dm-block-manager.c
+++ b/drivers/md/persistent-data/dm-block-manager.c
@@ -306,13 +306,13 @@ static void report_recursive_bug(dm_block_t b, int r)
 
 #else  /* !CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
 
-#define bl_init(x)
+#define bl_init(x) do { } while (0)
 #define bl_down_read(x) 0
 #define bl_down_read_nonblock(x) 0
-#define bl_up_read(x)
+#define bl_up_read(x) do { } while (0)
 #define bl_down_write(x) 0
-#define bl_up_write(x)
-#define report_recursive_bug(x, y)
+#define bl_up_write(x) do { } while (0)
+#define report_recursive_bug(x, y) do { } while (0)
 
 #endif /* CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
 
-- 
2.9.0