Throttle VM writeout in a cpuset aware way

This bases the vm throttling from the reclaim path on the dirty ratio
of the cpuset. Note that a cpuset is only effective if shrink_zone is called
from direct reclaim.

kswapd has a cpuset context that includes the whole machine. VM throttling
will only work during synchrononous reclaim and not  from kswapd.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.21-rc4-mm1/include/linux/writeback.h
===================================================================
--- linux-2.6.21-rc4-mm1.orig/include/linux/writeback.h	2007-03-20 16:06:46.000000000 -0700
+++ linux-2.6.21-rc4-mm1/include/linux/writeback.h	2007-03-20 16:07:51.000000000 -0700
@@ -85,7 +85,7 @@ static inline void wait_on_inode(struct 
 int wakeup_pdflush(long nr_pages, nodemask_t *nodes);
 void laptop_io_completion(void);
 void laptop_sync_completion(void);
-void throttle_vm_writeout(gfp_t gfp_mask);
+void throttle_vm_writeout(nodemask_t *nodes,gfp_t gfp_mask);
 
 extern struct timer_list laptop_mode_wb_timer;
 static inline int laptop_spinned_down(void)
Index: linux-2.6.21-rc4-mm1/mm/page-writeback.c
===================================================================
--- linux-2.6.21-rc4-mm1.orig/mm/page-writeback.c	2007-03-20 16:07:08.000000000 -0700
+++ linux-2.6.21-rc4-mm1/mm/page-writeback.c	2007-03-20 16:07:51.000000000 -0700
@@ -380,7 +380,7 @@ void balance_dirty_pages_ratelimited_nr(
 }
 EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
 
-void throttle_vm_writeout(gfp_t gfp_mask)
+void throttle_vm_writeout(nodemask_t *nodes, gfp_t gfp_mask)
 {
 	struct dirty_limits dl;
 
@@ -395,7 +395,7 @@ void throttle_vm_writeout(gfp_t gfp_mask
 	}
 
         for ( ; ; ) {
-		get_dirty_limits(&dl, NULL, &node_online_map);
+		get_dirty_limits(&dl, NULL, nodes);
 
                 /*
                  * Boost the allowable dirty threshold a bit for page
Index: linux-2.6.21-rc4-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.21-rc4-mm1.orig/mm/vmscan.c	2007-03-20 16:07:36.000000000 -0700
+++ linux-2.6.21-rc4-mm1/mm/vmscan.c	2007-03-20 16:07:51.000000000 -0700
@@ -1055,7 +1055,7 @@ static unsigned long shrink_zone(int pri
 		}
 	}
 
-	throttle_vm_writeout(sc->gfp_mask);
+	throttle_vm_writeout(&cpuset_current_mems_allowed, sc->gfp_mask);
 
 	atomic_dec(&zone->reclaim_in_progress);
 	return nr_reclaimed;