[POWERPC] hugepage BUG fix
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>
diff --git a/include/asm-powerpc/pgalloc.h b/include/asm-powerpc/pgalloc.h
index 9f0917c..ae63db7 100644
--- a/include/asm-powerpc/pgalloc.h
+++ b/include/asm-powerpc/pgalloc.h
@@ -117,7 +117,7 @@
pte_free_kernel(page_address(ptepage));
}
-#define PGF_CACHENUM_MASK 0xf
+#define PGF_CACHENUM_MASK 0x3
typedef struct pgtable_free {
unsigned long val;