linux-kernel - Re: [GIT PULL] block updates for 2.6.31-rc1

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Message-Id: <20090617151754.e7c4c58c.akpm@linux-foundation.org>
Date:	Wed, 17 Jun 2009 15:17:54 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [GIT PULL] block updates for 2.6.31-rc1

On Tue, 16 Jun 2009 09:18:23 +0200
Jens Axboe <jens.axboe@...cle.com> wrote:

> Martin K. Petersen (1):
>       block: Introduce helper to reset queue limits to default values

i386 allnoconfig:

block/blk-settings.c: In function 'blk_set_default_limits':
block/blk-settings.c:115: warning: large integer implicitly truncated to unsigned type

The patch was sent on June 12, acked on June 15, merged into mainline
June 16 and never made an appearance in linux-next.

It doesn't look like it'll cause any runtime problems, but that just
means we got lucky.  

Suggested fix is to use plain old "-1", rather than (incorrectly)
guessing what type the caller might be assigning to.

--- a/include/linux/blkdev.h~a
+++ a/include/linux/blkdev.h
@@ -702,7 +702,7 @@ extern unsigned long blk_max_low_pfn, bl
 #else
 #define BLK_BOUNCE_HIGH		-1ULL
 #endif
-#define BLK_BOUNCE_ANY		(-1ULL)
+#define BLK_BOUNCE_ANY		(-1)
 #define BLK_BOUNCE_ISA		(ISA_DMA_THRESHOLD)

 /*
_

Or is the code just buggy?  What are the units of BLK_BOUNCE_HIGH,
BLK_BOUNCE_ANY and BLK_BOUNCE_ISA?  Seems that they are physical
addresses.  So why are we copying one of these onto a variable which
records pfns?

If BLK_BOUNCE_ANY's units are indeed pfns (not the case afaict) then
using a ULL was inappropriate.

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