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[POWERPC] hugepage BUG fix

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On Tue, 2006-08-15 at 08:22 -0700, Dave Hansen wrote:
> kernel BUG in cache_free_debugcheck at mm/slab.c:2748!

Alright, this one is only triggered when slab debugging is enabled.  The
slabs are assumed to be aligned on a HUGEPTE_TABLE_SIZE boundary.  The free
path makes use of this assumption and uses the lowest nibble to pass around
an index into an array of kmem_cache pointers.  With slab debugging turned
on, the slab is still aligned, but the "working" object pointer is not.
This would break the assumption above that a full nibble is available for
the PGF_CACHENUM_MASK.

The following patch reduces PGF_CACHENUM_MASK to cover only the two least
significant bits, which is enough to cover the current number of 4 pgtable
cache types.  Then use this constant to mask out the appropriate part of
the huge pte pointer.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Adam Litke 2006-08-18 11:22:21 -07:00 committed by Paul Mackerras
parent d55c4a76f2
commit c9169f8747
2 changed files with 2 additions and 2 deletions
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2
arch/powerpc/mm/hugetlbpage.c
View file

@ -153,7 +153,7 @@ static void free_hugepte_range(struct mmu_gather *tlb, hugepd_t *hpdp)
hpdp->pd = 0;
tlb->need_flush = 1;
pgtable_free_tlb(tlb, pgtable_free_cache(hugepte, HUGEPTE_CACHE_NUM,
HUGEPTE_TABLE_SIZE-1));
PGF_CACHENUM_MASK));
}
#ifdef CONFIG_PPC_64K_PAGES

2
include/asm-powerpc/pgalloc.h
View file

@ -117,7 +117,7 @@ static inline void pte_free(struct page *ptepage)
pte_free_kernel(page_address(ptepage));
}
#define PGF_CACHENUM_MASK 0xf
#define PGF_CACHENUM_MASK 0x3
typedef struct pgtable_free {
unsigned long val;