[PATCH] call mm/page-writeback.c:set_ratelimit() when new pages are hot-added

ratelimit_pages in page-writeback.c is recalculated (in set_ratelimit())
every time a CPU is hot-added/removed.  But this value is not recalculated
when new pages are hot-added.

This patch fixes that problem by calling set_ratelimit() when new pages
are hot-added.

[akpm@osdl.org: cleanups]
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/writeback.h

@@ -117,6 +117,7 @@ int sync_page_range(struct inode *inode, struct address_space *mapping,
 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
 			   loff_t pos, loff_t count);
 void set_page_dirty_balance(struct page *page);
+void writeback_set_ratelimit(void);
 
 /* pdflush.c */
 extern int nr_pdflush_threads;	/* Global so it can be exported to sysctl

mm/memory_hotplug.c

@@ -13,6 +13,7 @@
 #include <linux/compiler.h>
 #include <linux/module.h>
 #include <linux/pagevec.h>
+#include <linux/writeback.h>
 #include <linux/slab.h>
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
@@ -192,6 +193,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
 	if (need_zonelists_rebuild)
 		build_all_zonelists();
 	vm_total_pages = nr_free_pagecache_pages();
+	writeback_set_ratelimit();
 	return 0;
 }
 

mm/page-writeback.c

@@ -501,7 +501,7 @@ void laptop_sync_completion(void)
  * will write six megabyte chunks, max.
  */
 
-static void set_ratelimit(void)
+void writeback_set_ratelimit(void)
 {
 	ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
 	if (ratelimit_pages < 16)
@@ -513,7 +513,7 @@ static void set_ratelimit(void)
 static int __cpuinit
 ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
 {
-	set_ratelimit();
+	writeback_set_ratelimit();
 	return 0;
 }
 
@@ -546,7 +546,7 @@ void __init page_writeback_init(void)
 			vm_dirty_ratio = 1;
 	}
 	mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
-	set_ratelimit();
+	writeback_set_ratelimit();
 	register_cpu_notifier(&ratelimit_nb);
 }