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From: Dave Hansen <dave@linux.vnet.ibm.com>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave@linux.vnet.ibm.com>
Subject: [PATCH] make sparse happy with gfp.h
Date: Thu, 14 Apr 2011 16:42:17 -0700	[thread overview]
Message-ID: <20110414234216.9E31DBD9@kernel> (raw)


Running sparse on page_alloc.c today, it errors out:
        include/linux/gfp.h:254:17: error: bad constant expression
        include/linux/gfp.h:254:17: error: cannot size expression

which is a line in gfp_zone():

        BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);

That's really unfortunate, because it ends up hiding all of the other
legitimate sparse messages like this:
        mm/page_alloc.c:5315:59: warning: incorrect type in argument 1 (different base types)
        mm/page_alloc.c:5315:59:    expected unsigned long [unsigned] [usertype] size
        mm/page_alloc.c:5315:59:    got restricted gfp_t [usertype] <noident>
...

Having sparse be able to catch these very oopsable bugs is a lot more
important than keeping a BUILD_BUG_ON().  Kill the BUILD_BUG_ON().

Compiles on x86_64 with and without CONFIG_DEBUG_VM=y.  defconfig
boots fine for me.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
---

 linux-2.6.git-dave/include/linux/gfp.h |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff -puN include/linux/gfp.h~make-sparse-happy-with-gfp_h include/linux/gfp.h
--- linux-2.6.git/include/linux/gfp.h~make-sparse-happy-with-gfp_h	2011-04-14 14:47:02.629275904 -0700
+++ linux-2.6.git-dave/include/linux/gfp.h	2011-04-14 14:47:38.813272674 -0700
@@ -249,14 +249,9 @@ static inline enum zone_type gfp_zone(gf
 
 	z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) &
 					 ((1 << ZONES_SHIFT) - 1);
-
-	if (__builtin_constant_p(bit))
-		BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
-	else {
 #ifdef CONFIG_DEBUG_VM
-		BUG_ON((GFP_ZONE_BAD >> bit) & 1);
+	BUG_ON((GFP_ZONE_BAD >> bit) & 1);
 #endif
-	}
 	return z;
 }
 
_

WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave@linux.vnet.ibm.com>
Subject: [PATCH] make sparse happy with gfp.h
Date: Thu, 14 Apr 2011 16:42:17 -0700	[thread overview]
Message-ID: <20110414234216.9E31DBD9@kernel> (raw)


Running sparse on page_alloc.c today, it errors out:
        include/linux/gfp.h:254:17: error: bad constant expression
        include/linux/gfp.h:254:17: error: cannot size expression

which is a line in gfp_zone():

        BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);

That's really unfortunate, because it ends up hiding all of the other
legitimate sparse messages like this:
        mm/page_alloc.c:5315:59: warning: incorrect type in argument 1 (different base types)
        mm/page_alloc.c:5315:59:    expected unsigned long [unsigned] [usertype] size
        mm/page_alloc.c:5315:59:    got restricted gfp_t [usertype] <noident>
...

Having sparse be able to catch these very oopsable bugs is a lot more
important than keeping a BUILD_BUG_ON().  Kill the BUILD_BUG_ON().

Compiles on x86_64 with and without CONFIG_DEBUG_VM=y.  defconfig
boots fine for me.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
---

 linux-2.6.git-dave/include/linux/gfp.h |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff -puN include/linux/gfp.h~make-sparse-happy-with-gfp_h include/linux/gfp.h
--- linux-2.6.git/include/linux/gfp.h~make-sparse-happy-with-gfp_h	2011-04-14 14:47:02.629275904 -0700
+++ linux-2.6.git-dave/include/linux/gfp.h	2011-04-14 14:47:38.813272674 -0700
@@ -249,14 +249,9 @@ static inline enum zone_type gfp_zone(gf
 
 	z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) &
 					 ((1 << ZONES_SHIFT) - 1);
-
-	if (__builtin_constant_p(bit))
-		BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
-	else {
 #ifdef CONFIG_DEBUG_VM
-		BUG_ON((GFP_ZONE_BAD >> bit) & 1);
+	BUG_ON((GFP_ZONE_BAD >> bit) & 1);
 #endif
-	}
 	return z;
 }
 
_

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             reply	other threads:[~2011-04-14 23:42 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-14 23:42 Dave Hansen [this message]
2011-04-14 23:42 ` [PATCH] make sparse happy with gfp.h Dave Hansen
2011-04-15  3:14 ` KOSAKI Motohiro
2011-04-15  3:14   ` KOSAKI Motohiro
2011-04-15  5:07   ` Dave Hansen
2011-04-15  5:07     ` Dave Hansen
2011-04-15  5:33     ` KOSAKI Motohiro
2011-04-15  5:33       ` KOSAKI Motohiro
2011-04-15 14:27       ` [PATCH] fix sparse happy borkage when including gfp.h Dave Hansen
2011-04-15 14:27         ` Dave Hansen
2011-04-26  9:24         ` Christopher Li
2011-04-15  5:09   ` [PATCH] define dummy BUILD_BUG_ON definition for sparse KOSAKI Motohiro
2011-04-15  5:09     ` KOSAKI Motohiro
2011-04-15  5:11     ` [PATCH] define __must_be_array() for __CHECKER__ KOSAKI Motohiro
2011-04-15  5:11       ` KOSAKI Motohiro
2011-04-15  5:11     ` [PATCH] Undef __compiletime_{warning,error} if __CHECKER__ is defined KOSAKI Motohiro
2011-04-15  5:11       ` KOSAKI Motohiro

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