From: Andy Whitcroft <apw@shadowen.org>
For each node there are a defined list of MAX_NR_ZONES zones. These are
selected as a result of the __GFP_DMA and __GFP_HIGHMEM zone modifier flags
being passed to the memory allocator as part of the GFP mask. Each node
has a set of zone lists, node_zonelists, which defines the list and order
of zones to scan for each flag combination. When initialising these lists
we iterate over modifier combinations 0 .. MAX_NR_ZONES. However, this is
only correct when there are at most ZONES_SHIFT flags. If another flag is
introduced zonelists for it would not be initialised.
This patch introduces GFP_ZONETYPES (based on GFP_ZONEMASK) as a bound for
the number of modifier combinations.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/mmzone.h | 29 ++++++++++++++++++++++++++++-
25-akpm/mm/page_alloc.c | 8 ++++----
2 files changed, 32 insertions(+), 5 deletions(-)
diff -puN include/linux/mmzone.h~fix-gfp-zone-modifier-interators include/linux/mmzone.h
--- 25/include/linux/mmzone.h~fix-gfp-zone-modifier-interators Fri Jun 25 14:35:51 2004
+++ 25-akpm/include/linux/mmzone.h Fri Jun 25 14:35:51 2004
@@ -81,7 +81,34 @@ struct per_cpu_pageset {
#define MAX_NR_ZONES 3 /* Sync this with ZONES_SHIFT */
#define ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */
+
+/*
+ * When a memory allocation must conform to specific limitations (such
+ * as being suitable for DMA) the caller will pass in hints to the
+ * allocator in the gfp_mask, in the zone modifier bits. These bits
+ * are used to select a priority ordered list of memory zones which
+ * match the requested limits. GFP_ZONEMASK defines which bits within
+ * the gfp_mask should be considered as zone modifiers. Each valid
+ * combination of the zone modifier bits has a corresponding list
+ * of zones (in node_zonelists). Thus for two zone modifiers there
+ * will be a maximum of 4 (2 ** 2) zonelists, for 3 modifiers there will
+ * be 8 (2 ** 3) zonelists. GFP_ZONETYPES defines the number of possible
+ * combinations of zone modifiers in "zone modifier space".
+ */
#define GFP_ZONEMASK 0x03
+/*
+ * As an optimisation any zone modifier bits which are only valid when
+ * no other zone modifier bits are set (loners) should be placed in
+ * the highest order bits of this field. This allows us to reduce the
+ * extent of the zonelists thus saving space. For example in the case
+ * of three zone modifier bits, we could require up to eight zonelists.
+ * If the left most zone modifier is a "loner" then the highest valid
+ * zonelist would be four allowing us to allocate only five zonelists.
+ * Use the first form when the left most bit is not a "loner", otherwise
+ * use the second.
+ */
+/* #define GFP_ZONETYPES (GFP_ZONEMASK + 1) */ /* Non-loner */
+#define GFP_ZONETYPES ((GFP_ZONEMASK + 1) / 2 + 1) /* Loner */
/*
* On machines where it is needed (eg PCs) we divide physical memory
@@ -237,7 +264,7 @@ struct zonelist {
struct bootmem_data;
typedef struct pglist_data {
struct zone node_zones[MAX_NR_ZONES];
- struct zonelist node_zonelists[MAX_NR_ZONES];
+ struct zonelist node_zonelists[GFP_ZONETYPES];
int nr_zones;
struct page *node_mem_map;
struct bootmem_data *bdata;
diff -puN mm/page_alloc.c~fix-gfp-zone-modifier-interators mm/page_alloc.c
--- 25/mm/page_alloc.c~fix-gfp-zone-modifier-interators Fri Jun 25 14:35:51 2004
+++ 25-akpm/mm/page_alloc.c Fri Jun 25 14:35:51 2004
@@ -1235,7 +1235,7 @@ static void __init build_zonelists(pg_da
DECLARE_BITMAP(used_mask, MAX_NUMNODES);
/* initialize zonelists */
- for (i = 0; i < MAX_NR_ZONES; i++) {
+ for (i = 0; i < GFP_ZONETYPES; i++) {
zonelist = pgdat->node_zonelists + i;
memset(zonelist, 0, sizeof(*zonelist));
zonelist->zones[0] = NULL;
@@ -1257,7 +1257,7 @@ static void __init build_zonelists(pg_da
node_load[node] += load;
prev_node = node;
load--;
- for (i = 0; i < MAX_NR_ZONES; i++) {
+ for (i = 0; i < GFP_ZONETYPES; i++) {
zonelist = pgdat->node_zonelists + i;
for (j = 0; zonelist->zones[j] != NULL; j++);
@@ -1280,7 +1280,7 @@ static void __init build_zonelists(pg_da
int i, j, k, node, local_node;
local_node = pgdat->node_id;
- for (i = 0; i < MAX_NR_ZONES; i++) {
+ for (i = 0; i < GFP_ZONETYPES; i++) {
struct zonelist *zonelist;
zonelist = pgdat->node_zonelists + i;
@@ -1840,7 +1840,7 @@ static void setup_per_zone_protection(vo
* For each of the different allocation types:
* GFP_DMA -> GFP_KERNEL -> GFP_HIGHMEM
*/
- for (i = 0; i < MAX_NR_ZONES; i++) {
+ for (i = 0; i < GFP_ZONETYPES; i++) {
/*
* For each of the zones:
* ZONE_HIGHMEM -> ZONE_NORMAL -> ZONE_DMA
_