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 and will
therefore not throttle unless global limits are reached.

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

Index: linux-2.6.20-rc4-mm1/include/linux/writeback.h
===================================================================
--- linux-2.6.20-rc4-mm1.orig/include/linux/writeback.h	2007-01-12 13:01:03.000000000 -0800
+++ linux-2.6.20-rc4-mm1/include/linux/writeback.h	2007-01-12 13:01:19.000000000 -0800
@@ -85,7 +85,7 @@
 int wakeup_pdflush(long nr_pages, nodemask_t *nodes);
 void laptop_io_completion(void);
 void laptop_sync_completion(void);
-void throttle_vm_writeout(void);
+void throttle_vm_writeout(nodemask_t *);
 
 extern struct timer_list laptop_mode_wb_timer;
 static inline int laptop_spinned_down(void)
Index: linux-2.6.20-rc4-mm1/mm/page-writeback.c
===================================================================
--- linux-2.6.20-rc4-mm1.orig/mm/page-writeback.c	2007-01-12 13:00:06.000000000 -0800
+++ linux-2.6.20-rc4-mm1/mm/page-writeback.c	2007-01-12 13:01:19.000000000 -0800
@@ -349,12 +349,12 @@
 }
 EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
 
-void throttle_vm_writeout(void)
+void throttle_vm_writeout(nodemask_t *nodes)
 {
 	struct dirty_limits dl;
 
         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-2.6.20-rc4-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.20-rc4-mm1.orig/mm/vmscan.c	2007-01-12 13:01:14.000000000 -0800
+++ linux-2.6.20-rc4-mm1/mm/vmscan.c	2007-01-12 13:01:19.000000000 -0800
@@ -1032,7 +1032,7 @@
 		}
 	}
 
-	throttle_vm_writeout();
+	throttle_vm_writeout(&cpuset_current_mems_allowed);
 
 	atomic_dec(&zone->reclaim_in_progress);
 	return nr_reclaimed;