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Re: [dm-devel] [PATCH]md:dm.c Fix warning: statement with no effect




On Jan 11, 2011, at 1:22 PM, Mike Snitzer wrote:

On Sun, Aug 01 2010 at  6:23pm -0400,
Justin P. Mattock <justinmattock gmail com> wrote:

On 07/31/2010 12:07 PM, Alasdair G Kergon wrote:
On Sat, Jul 31, 2010 at 12:05:04PM -0700, Justin P. Mattock wrote:
haven't heard any feedback on this any ideas?
Ive noticed that having CONFIG_BLK_DEV_INTEGRITY=n I get warning messages generated by GCC(below)
  CC      drivers/md/dm.o
drivers/md/dm.c: In function 'split_bvec':
drivers/md/dm.c:1117:3: warning: statement with no effect
drivers/md/dm.c: In function 'clone_bio':
drivers/md/dm.c:1145:3: warning: statement with no effect

I'd suggest hiding it inside the .h files and not trying to scatter #ifdefs
throughout the code.

Alasdair




o.k. this ones a bit tricky.. but I did finally get this to build clean.
below is an updated patch that gets me to build clean. Let me know
if something other than this should be used.(or if this is a good
solution then let me know and I'll resend)

<---cut--->

When building the kernel with CONFIG_BLK_DEV_INTEGRITY=n everything
gets sent(if Im reading this correctly) too:
(line #660 bio.h)
#else /* CONFIG_BLK_DEV_INTEGRITY */

#define bio_integrity(a)		(0)
#define bioset_integrity_create(a, b)	(0)
#define bio_integrity_prep(a)		(0)
#define bio_integrity_enabled(a)	(0)
#define bio_integrity_clone(a, b, c, d)	(0)
#define bioset_integrity_free(a)	do { } while (0)
#define bio_integrity_free(a, b)	do { } while (0)
#define bio_integrity_endio(a, b)	do { } while (0)
#define bio_integrity_advance(a, b)	do { } while (0)
#define bio_integrity_trim(a, b, c)	do { } while (0)
#define bio_integrity_split(a, b, c)	do { } while (0)
#define bio_integrity_set_tag(a, b, c)	do { } while (0)
#define bio_integrity_get_tag(a, b, c)	do { } while (0)
#define bio_integrity_init(a)		do { } while (0)

changing #else preprocessor to #elif ! defined(CONFIG_BLK_DEV_INTEGRITY)
opposite of #if defined(CONFIG_BLK_DEV_INTEGRITY)
gets me to build dm.c without the warning message.
please have a look when you have time and let me know if this is a good
solution to this.

I'm not seeing any warnings.  My .config has:
# CONFIG_BLK_DEV_INTEGRITY is not set

The bio.h block is:

#if defined(CONFIG_BLK_DEV_INTEGRITY)
...
#else /* CONFIG_BLK_DEV_INTEGRITY */
#define bio_integrity_clone(a, b, c, d)       (0)
#endif

So I'm not seeing why your proposed change matters.  Should already
behave properly (and in practice I'm not seeing any problems).


right now, I am not running that system(clfs) that this was showing up on i.e. built with gcc 4.6.* (august) What I can do is load that one up(when I have some free time) and see if this shows up again with the latest
gcc



Signed-off-by: Justin P. Mattock <justinmattock gmail com>

---
include/linux/bio.h |    2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7fc5606..a8259c8 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -657,7 +657,7 @@ extern int bioset_integrity_create(struct
bio_set *, int);
extern void bioset_integrity_free(struct bio_set *);
extern void bio_integrity_init(void);

-#else /* CONFIG_BLK_DEV_INTEGRITY */
+#elif !defined(CONFIG_BLK_DEV_INTEGRITY) /* CONFIG_BLK_DEV_INTEGRITY */

#define bio_integrity(a)		(0)
#define bioset_integrity_create(a, b)	(0)
-- 1.7.1.rc1.21.gf3bd6

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Justin P. Mattock


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