[PATCH] NUMA: Add zone_to_nid function

There are many places where we need to determine the node of a zone.
Currently we use a difficult to read sequence of pointer dereferencing.
Put that into an inline function and use throughout VM.  Maybe we can find
a way to optimize the lookup in the future.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/mm/discontig.c

@@ -422,7 +422,7 @@ void __init set_highmem_pages_init(int bad_ppro)
 		zone_end_pfn = zone_start_pfn + zone->spanned_pages;
 
 		printk("Initializing %s for node %d (%08lx:%08lx)\n",
-				zone->name, zone->zone_pgdat->node_id,
+				zone->name, zone_to_nid(zone),
 				zone_start_pfn, zone_end_pfn);
 
 		for (node_pfn = zone_start_pfn; node_pfn < zone_end_pfn; node_pfn++) {

arch/parisc/mm/init.c

@@ -551,7 +551,7 @@ void show_mem(void)
 
 				printk("Zone list for zone %d on node %d: ", j, i);
 				for (k = 0; zl->zones[k] != NULL; k++) 
-					printk("[%d/%s] ", zl->zones[k]->zone_pgdat->node_id, zl->zones[k]->name);
+					printk("[%d/%s] ", zone_to_nid(zl->zones[k]), zl->zones[k]->name);
 				printk("\n");
 			}
 		}

include/linux/mm.h

@@ -499,12 +499,17 @@ static inline struct zone *page_zone(struct page *page)
 	return zone_table[page_zone_id(page)];
 }
 
+static inline unsigned long zone_to_nid(struct zone *zone)
+{
+	return zone->zone_pgdat->node_id;
+}
+
 static inline unsigned long page_to_nid(struct page *page)
 {
 	if (FLAGS_HAS_NODE)
 		return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
 	else
-		return page_zone(page)->zone_pgdat->node_id;
+		return zone_to_nid(page_zone(page));
 }
 static inline unsigned long page_to_section(struct page *page)
 {

kernel/cpuset.c

@@ -2245,7 +2245,7 @@ int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
 	int i;
 
 	for (i = 0; zl->zones[i]; i++) {
-		int nid = zl->zones[i]->zone_pgdat->node_id;
+		int nid = zone_to_nid(zl->zones[i]);
 
 		if (node_isset(nid, current->mems_allowed))
 			return 1;
@@ -2318,7 +2318,7 @@ int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
 
 	if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
 		return 1;
-	node = z->zone_pgdat->node_id;
+	node = zone_to_nid(z);
 	might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
 	if (node_isset(node, current->mems_allowed))
 		return 1;

mm/hugetlb.c

@@ -72,7 +72,7 @@ static struct page *dequeue_huge_page(struct vm_area_struct *vma,
 	struct zone **z;
 
 	for (z = zonelist->zones; *z; z++) {
-		nid = (*z)->zone_pgdat->node_id;
+		nid = zone_to_nid(*z);
 		if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
 		    !list_empty(&hugepage_freelists[nid]))
 			break;

mm/mempolicy.c

@@ -487,7 +487,7 @@ static void get_zonemask(struct mempolicy *p, nodemask_t *nodes)
 	switch (p->policy) {
 	case MPOL_BIND:
 		for (i = 0; p->v.zonelist->zones[i]; i++)
-			node_set(p->v.zonelist->zones[i]->zone_pgdat->node_id,
+			node_set(zone_to_nid(p->v.zonelist->zones[i]),
 				*nodes);
 		break;
 	case MPOL_DEFAULT:
@@ -1145,7 +1145,7 @@ unsigned slab_node(struct mempolicy *policy)
 		 * Follow bind policy behavior and start allocation at the
 		 * first node.
 		 */
-		return policy->v.zonelist->zones[0]->zone_pgdat->node_id;
+		return zone_to_nid(policy->v.zonelist->zones[0]);
 
 	case MPOL_PREFERRED:
 		if (policy->v.preferred_node >= 0)
@@ -1649,7 +1649,7 @@ void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
 
 		nodes_clear(nodes);
 		for (z = pol->v.zonelist->zones; *z; z++)
-			node_set((*z)->zone_pgdat->node_id, nodes);
+			node_set(zone_to_nid(*z), nodes);
 		nodes_remap(tmp, nodes, *mpolmask, *newmask);
 		nodes = tmp;
 

mm/oom_kill.c

@@ -177,8 +177,7 @@ static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
 
 	for (z = zonelist->zones; *z; z++)
 		if (cpuset_zone_allowed(*z, gfp_mask))
-			node_clear((*z)->zone_pgdat->node_id,
-					nodes);
+			node_clear(zone_to_nid(*z), nodes);
 		else
 			return CONSTRAINT_CPUSET;
 

mm/page_alloc.c

@@ -1217,7 +1217,7 @@ unsigned int nr_free_pagecache_pages(void)
 #ifdef CONFIG_NUMA
 static void show_node(struct zone *zone)
 {
-	printk("Node %d ", zone->zone_pgdat->node_id);
+	printk("Node %ld ", zone_to_nid(zone));
 }
 #else
 #define show_node(zone)	do { } while (0)

mm/vmscan.c

@@ -1661,7 +1661,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 	 * over remote processors and spread off node memory allocations
 	 * as wide as possible.
 	 */
-	node_id = zone->zone_pgdat->node_id;
+	node_id = zone_to_nid(zone);
 	mask = node_to_cpumask(node_id);
 	if (!cpus_empty(mask) && node_id != numa_node_id())
 		return 0;