2014-02-13 02:21:36

by Patrick Palka

Subject: [PATCH] ext4: address a benign compiler warning

When !defined(CONFIG_EXT4_DEBUG), mb_debug() should be defined as an
empty do-while statement so as to suppress the following compiler
warning:

fs/ext4/mballoc.c: In function ‘ext4_mb_cleanup_pa’:
fs/ext4/mballoc.c:2659:47: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
mb_debug(1, "mballoc: %u PAs left\n", count);

Signed-off-by: Patrick Palka <[email protected]>
---
fs/ext4/mballoc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 08481ee..92eeb98 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -48,7 +48,7 @@ extern ushort ext4_mballoc_debug;
} \
} while (0)
#else
-#define mb_debug(n, fmt, a...)
+#define mb_debug(n, fmt, a...) do { } while (0)
#endif

#define EXT4_MB_HISTORY_ALLOC 1 /* allocation */
--
1.9.0.rc3

2014-02-13 02:59:48

by Joe Perches

Subject: Re: [PATCH] ext4: address a benign compiler warning

On Wed, 2014-02-12 at 21:13 -0500, Patrick Palka wrote:
> When !defined(CONFIG_EXT4_DEBUG), mb_debug() should be defined as an
> empty do-while statement so as to suppress the following compiler
> warning:

Hello Patrick.

> fs/ext4/mballoc.c: In function ‘ext4_mb_cleanup_pa’:
> fs/ext4/mballoc.c:2659:47: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
> mb_debug(1, "mballoc: %u PAs left\n", count);
> ---
> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
[]
> @@ -48,7 +48,7 @@ extern ushort ext4_mballoc_debug;
> } \
> } while (0)
> #else
> -#define mb_debug(n, fmt, a...)
> +#define mb_debug(n, fmt, a...) do { } while (0)

Ideally, this section should be something like below
so the !CONFIG_EXT4_DEBUG case still verifies that
the format and argument types match.

This can help avoid people adding debug statements but
not compiling with the proper CONFIG_<foo> variable set.

---

#ifdef CONFIG_EXT4_DEBUG
extern ushort ext4_mballoc_debug;

#define mb_debug(n, fmt, ...) \
do { \
if ((n) <= ext4_mballoc_debug) \
pr_debug(fmt, ##__VA_ARGS__); \
} \
} while (0)
#else
#define mb_debug(n, fmt, ...) \
no_printk(KERN_DEBUG fmt, ##__VA_ARGS__)
#endif

2014-02-13 04:03:06

by Patrick Palka

Subject: Re: [PATCH] ext4: address a benign compiler warning

On Wed, Feb 12, 2014 at 9:59 PM, Joe Perches <[email protected]> wrote:
> On Wed, 2014-02-12 at 21:13 -0500, Patrick Palka wrote:
>> When !defined(CONFIG_EXT4_DEBUG), mb_debug() should be defined as an
>> empty do-while statement so as to suppress the following compiler
>> warning:
>
> Hello Patrick.
>
>> fs/ext4/mballoc.c: In function 'ext4_mb_cleanup_pa':
>> fs/ext4/mballoc.c:2659:47: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
>> mb_debug(1, "mballoc: %u PAs left\n", count);
>> ---
>> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
> []
>> @@ -48,7 +48,7 @@ extern ushort ext4_mballoc_debug;
>> } \
>> } while (0)
>> #else
>> -#define mb_debug(n, fmt, a...)
>> +#define mb_debug(n, fmt, a...) do { } while (0)
>
> Ideally, this section should be something like below
> so the !CONFIG_EXT4_DEBUG case still verifies that
> the format and argument types match.
>
> This can help avoid people adding debug statements but
> not compiling with the proper CONFIG_<foo> variable set.
>
> ---
>
> #ifdef CONFIG_EXT4_DEBUG
> extern ushort ext4_mballoc_debug;
>
> #define mb_debug(n, fmt, ...) \
> do { \
> if ((n) <= ext4_mballoc_debug) \
> pr_debug(fmt, ##__VA_ARGS__); \
> } \
> } while (0)
> #else
> #define mb_debug(n, fmt, ...) \
> no_printk(KERN_DEBUG fmt, ##__VA_ARGS__)
> #endif
>
>

Hi Joe,

Thanks! I was not aware of that idiom. It makes a good amount of
sense. I'm going to send a revised version of the patch shortly.

Patrick

2014-02-13 04:12:25

by Patrick Palka

Subject: [PATCH] ext4: address a benign compiler warning

When !defined(CONFIG_EXT4_DEBUG), mb_debug() should be defined as a
no_printk() statement instead of an empty statement in order to suppress
the following compiler warning:

fs/ext4/mballoc.c: In function ‘ext4_mb_cleanup_pa’:
fs/ext4/mballoc.c:2659:47: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
mb_debug(1, "mballoc: %u PAs left\n", count);

Signed-off-by: Patrick Palka <[email protected]>
---
fs/ext4/mballoc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 08481ee..9347328 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -48,7 +48,7 @@ extern ushort ext4_mballoc_debug;
} \
} while (0)
#else
-#define mb_debug(n, fmt, a...)
+#define mb_debug(n, fmt, a...) no_printk(fmt, ## a)
#endif

#define EXT4_MB_HISTORY_ALLOC 1 /* allocation */
--
1.9.0.rc3

2014-02-18 01:44:04

by Theodore Ts'o

Subject: Re: [PATCH] ext4: address a benign compiler warning

On Wed, Feb 12, 2014 at 11:12:04PM -0500, Patrick Palka wrote:
> When !defined(CONFIG_EXT4_DEBUG), mb_debug() should be defined as a
> no_printk() statement instead of an empty statement in order to suppress
> the following compiler warning:
>
> fs/ext4/mballoc.c: In function ‘ext4_mb_cleanup_pa’:
> fs/ext4/mballoc.c:2659:47: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
> mb_debug(1, "mballoc: %u PAs left\n", count);
>
> Signed-off-by: Patrick Palka <[email protected]>

Thanks, applied.

- Ted