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SLUB: Fix build breakage in linux/mm_types.h

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On Wed, 6 Jul 2011, Jonathan Cameron wrote:

> Getting:
>
>   CHK     include/linux/version.h
>   CHK     include/generated/utsrelease.h
> make[1]: `include/generated/mach-types.h' is up to date.
>   CC      arch/arm/kernel/asm-offsets.s
> In file included from include/linux/sched.h:64:0,
>                  from arch/arm/kernel/asm-offsets.c:13:
> include/linux/mm_types.h:74:15: error: duplicate member '_count'
> make[1]: *** [arch/arm/kernel/asm-offsets.s] Error 1
> make: *** [prepare0] Error 2
>
> Issue looks to have been introduced by
>
>     mm: Rearrange struct page
>
> fc9bb8c768
>
> Guessing it's a known issue, but just thought I'd flag it up in case
> it's something very specific about my build.
>
> gcc-2.6 armv7a
>
> Reverting that patch works, but given I don't know the history, I'm
> not proposing doing that in general!

Well _count exists in two unionized structs but always has the same offset
within the larger struct. Maybe ARM creates different offsets there for
some reason?

The following is a patch to restructure the union / structs combo in such
a way that only a single definition of _count

Reported-by: Jonathan Cameron <jic23@cam.ac.uk>
Tested-by: Piotr Hosowicz <piotr@hosowicz.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Christoph Lameter 2011-07-06 09:46:18 -05:00 committed by Pekka Enberg
parent 9da4714a2d
commit ea6bd8ee1a
1 changed files with 10 additions and 15 deletions
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25
include/linux/mm_types.h
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@ -49,32 +49,27 @@ struct page {
* see PAGE_MAPPING_ANON below. * see PAGE_MAPPING_ANON below.
*/ */
/* Second double word */ /* Second double word */
union { struct {
struct { union {
pgoff_t index; /* Our offset within mapping. */ pgoff_t index; /* Our offset within mapping. */
void *freelist; /* slub first free object */
};
union {
atomic_t _mapcount; /* Count of ptes mapped in mms, atomic_t _mapcount; /* Count of ptes mapped in mms,
* to show when page is mapped * to show when page is mapped
* & limit reverse map searches. * & limit reverse map searches.
*/ */
atomic_t _count; /* Usage count, see below. */
};
struct { /* SLUB cmpxchg_double area */ /* Used for cmpxchg_double in slub */
void *freelist; unsigned long counters;
union { struct {
unsigned long counters;
struct {
unsigned inuse:16; unsigned inuse:16;
unsigned objects:15; unsigned objects:15;
unsigned frozen:1; unsigned frozen:1;
/*
* Kernel may make use of this field even when slub
* uses the rest of the double word!
*/
atomic_t _count;
};
}; };
}; };
atomic_t _count; /* Usage count, see below. */
}; };
/* Third double word block */ /* Third double word block */