From: Adam Litke 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 Cc: Paul Mackerras Signed-off-by: Andrew Morton --- arch/powerpc/mm/hugetlbpage.c | 2 +- include/asm-powerpc/pgalloc.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff -puN arch/powerpc/mm/hugetlbpage.c~powerpc-hugepage-bug-fix arch/powerpc/mm/hugetlbpage.c --- a/arch/powerpc/mm/hugetlbpage.c~powerpc-hugepage-bug-fix +++ a/arch/powerpc/mm/hugetlbpage.c @@ -153,7 +153,7 @@ static void free_hugepte_range(struct mm 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 diff -puN include/asm-powerpc/pgalloc.h~powerpc-hugepage-bug-fix include/asm-powerpc/pgalloc.h --- a/include/asm-powerpc/pgalloc.h~powerpc-hugepage-bug-fix +++ a/include/asm-powerpc/pgalloc.h @@ -117,7 +117,7 @@ static inline void pte_free(struct page pte_free_kernel(page_address(ptepage)); } -#define PGF_CACHENUM_MASK 0xf +#define PGF_CACHENUM_MASK 0x3 typedef struct pgtable_free { unsigned long val; _