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
>
> fc9bb8c768abe7ae10861c3510e01a95f98d5933
>
> 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
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
---
include/linux/mm_types.h | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)
Index: linux-2.6/include/linux/mm_types.h
===================================================================
--- linux-2.6.orig/include/linux/mm_types.h 2011-07-06 09:35:10.078120512 -0500
+++ linux-2.6/include/linux/mm_types.h 2011-07-06 09:44:47.388116815 -0500
@@ -49,32 +49,27 @@ struct page {
* see PAGE_MAPPING_ANON below.
*/
/* Second double word */
- union {
- struct {
+ struct {
+ union {
pgoff_t index; /* Our offset within mapping. */
+ void *freelist; /* slub first free object */
+ };
+
+ union {
atomic_t _mapcount; /* Count of ptes mapped in mms,
* to show when page is mapped
* & limit reverse map searches.
*/
- atomic_t _count; /* Usage count, see below. */
- };
- struct { /* SLUB cmpxchg_double area */
- void *freelist;
- union {
- unsigned long counters;
- struct {
+ /* Used for cmpxchg_double in slub */
+ unsigned long counters;
+ struct {
unsigned inuse:16;
unsigned objects:15;
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 */
--
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