[PATCH: 012/017]Memory hotplug for new nodes v.4.(rebuild zonelists after online pages)

[PATCH: 012/017]Memory hotplug for new nodes v.4.(rebuild zonelists after online pages)

[Yasunori Goto]

In current code, zonelist is considered to be build once, no modification.
But MemoryHotplug can add new zone/pgdat. It must be updated.

This patch modifies build_all_zonelists(). 
By this, build_all_zonelist() can reconfig pgdat's zonelists.

To update them safety, this patch use stop_machine_run().
Other cpus don't touch among updating them by using it.

In previous version (V2), kernel updated them after zone initialization.
But present_page of its new zone is still 0, because online_page()
is not called yet at this time. 
Build_zonelists() checks present_pages to find present zone.
It was too early. So, I changed it after online_pages().

Signed-off-by: Yasunori Goto     <y-goto@jp.fujitsu.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

 mm/memory_hotplug.c |   12 ++++++++++++
 mm/page_alloc.c     |   26 +++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

Index: pgdat8/mm/page_alloc.c
===================================================================
--- pgdat8.orig/mm/page_alloc.c	2006-03-17 13:53:39.194026730 +0900
+++ pgdat8/mm/page_alloc.c	2006-03-17 13:53:45.530940715 +0900
@@ -37,6 +37,7 @@
 #include <linux/nodemask.h>
 #include <linux/vmalloc.h>
 #include <linux/mempolicy.h>
+#include <linux/stop_machine.h>
 
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -1765,14 +1766,29 @@ static void __init build_zonelists(pg_da
 
 #endif	/* CONFIG_NUMA */
 
-void __init build_all_zonelists(void)
+/* return values int ....just for stop_machine_run() */
+static int __meminit __build_all_zonelists(void *dummy)
 {
-	int i;
+	int nid;
+	for_each_online_node(nid)
+		build_zonelists(NODE_DATA(nid));
+	return 0;
+}
+
+void __meminit build_all_zonelists(void)
+{
+	if (system_state == SYSTEM_BOOTING) {
+		__build_all_zonelists(0);
+		cpuset_init_current_mems_allowed();
+	} else {
+		/* we have to stop all cpus to guaranntee there is no user
+		   of zonelist */
+		stop_machine_run(__build_all_zonelists, NULL, NR_CPUS);
+		/* cpuset refresh routine should be here */
+	}
 
-	for_each_online_node(i)
-		build_zonelists(NODE_DATA(i));
 	printk("Built %i zonelists\n", num_online_nodes());
-	cpuset_init_current_mems_allowed();
+
 }
 
 /*
Index: pgdat8/mm/memory_hotplug.c
===================================================================
--- pgdat8.orig/mm/memory_hotplug.c	2006-03-17 13:53:38.274104866 +0900
+++ pgdat8/mm/memory_hotplug.c	2006-03-17 13:53:40.712581399 +0900
@@ -123,6 +123,7 @@ int online_pages(unsigned long pfn, unsi
 	unsigned long flags;
 	unsigned long onlined_pages = 0;
 	struct zone *zone;
+	int need_refresh_zonelist = 0;
 
 	/*
 	 * This doesn't need a lock to do pfn_to_page().
@@ -135,6 +136,14 @@ int online_pages(unsigned long pfn, unsi
 	grow_pgdat_span(zone->zone_pgdat, pfn, pfn + nr_pages);
 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
 
+	/*
+	 * If this zone is not populated, then it is not in zonelist.
+	 * This means the page allocator ignores this zone.
+	 * So, zonelist must be updated after online.
+	 */
+	if (!populated_zone(zone))
+		need_refresh_zonelist = 1;
+
 	for (i = 0; i < nr_pages; i++) {
 		struct page *page = pfn_to_page(pfn + i);
 		online_page(page);
@@ -145,6 +154,9 @@ int online_pages(unsigned long pfn, unsi
 
 	setup_per_zone_pages_min();
 
+	if (need_refresh_zonelist)
+		build_all_zonelists();
+
 	return 0;
 }
 

-- 
Yasunori Goto 


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Re: [PATCH: 012/017]Memory hotplug for new nodes v.4.(rebuild zonelists after online pages)

[Dave Hansen]

On Fri, 2006-03-17 at 17:22 +0900, Yasunori Goto wrote:
> +++ pgdat8/mm/memory_hotplug.c  2006-03-17 13:53:40.712581399 +0900
> @@ -123,6 +123,7 @@ int online_pages(unsigned long pfn, unsi
>         unsigned long flags;
>         unsigned long onlined_pages = 0;
>         struct zone *zone;
> +       int need_refresh_zonelist = 0; 

I'd make this "need_to_rebuild_zonelists" or "need_zonelists_rebuild".
I think those sound a little bit better.

Plus, it makes even more sense when you see:

       if (need_to_rebuild_zonelists)
               build_all_zonelists();

if the names all match up.

-- Dave

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