physnode_map definition should be signed

Hello Martin-san.

In your modification of pfn_valid() for IA32 at 2.6.4 stock kernel, it doesn't return 0 even if the node is offline.

True problem is physnode_map's definition.
Physnode_map[]'s default (offline) value is -1,
but it is defined as UNSIGNED 8.
So, pfn_to_nid() return 255.

I think this should be defined as signed like this patch. Maximum node number of IA32 is 16, so this is enough yet.

I found this problem on multi-node emulation for memory-hotplug test. When I started X on this emulation, system panicked at remap_pte_range() by this problem.
I think that system will be down when a program will call mmap() for hardware area.

Could you check this?
Or, Do you already know this problem?

Thanks.

-----------------------------------------------------------------

 mem_node_hotplug-goto/arch/i386/mm/discontig.c  |    2 +-
 mem_node_hotplug-goto/include/asm-i386/mmzone.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff -puN include/asm-i386/mmzone.h~phys_nodemap_modify include/asm-i386/mmzone.h
@@ -37,7 +37,7 @@ extern struct pglist_data *node_data[];
 #define MAX_ELEMENTS 256
 #define PAGES_PER_ELEMENT (MAX_NR_PAGES/MAX_ELEMENTS)
 
-extern u8 physnode_map[];
+extern s8 physnode_map[];
 
 static inline int pfn_to_nid(unsigned long pfn)
 {

diff -puN arch/i386/mm/discontig.c~phys_nodemap_modify arch/i386/mm/discontig.c
@@ -56,7 +56,7 @@ bootmem_data_t node0_bdata;
  *     physnode_map[4-7] = 1;
  *     physnode_map[8- ] = -1;
  */
-u8 physnode_map[MAX_ELEMENTS] = { [0 ... (MAX_ELEMENTS - 1)] = -1};
+s8 physnode_map[MAX_ELEMENTS] = { [0 ... (MAX_ELEMENTS - 1)] = -1};
 
 unsigned long node_start_pfn[MAX_NUMNODES];
 unsigned long node_end_pfn[MAX_NUMNODES];

Yasunori Goto <ygoto at us.fujitsu.com>

There are several breakages in this area, particularly on Summit with 4/4 split right now - in my tree I'm init'ing the array to 0 temporarily to get around some problems, but we have better fixes lined up.

Anyway, your patch looks correct - 128 nodes should be plenty. I shall apply it. Thanks,

M.