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Subject[PATCH RFC] hotplug-memory: refactor online_pages to separate zone growth from page onlining
The Xen balloon driver needs to separate the process of hot-installing
memory into two phases: one to allocate the page structures and
configure the zones, and another to actually online the pages of newly
installed memory.

This patch splits up the innards of online_pages() into two pieces which
correspond to these two phases. The behaviour of online_pages() itself
is unchanged.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
---
include/linux/memory_hotplug.h | 3 +
mm/memory_hotplug.c | 66 ++++++++++++++++++++++++++++++++--------
2 files changed, 57 insertions(+), 12 deletions(-)
===================================================================
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -57,7 +57,10 @@
/* need some defines for these for archs that don't support it */
extern void online_page(struct page *page);
/* VM interface that may be used by firmware interface */
+extern int prepare_online_pages(unsigned long pfn, unsigned long nr_pages);
+extern unsigned long mark_pages_onlined(unsigned long pfn, unsigned long nr_pages);
extern int online_pages(unsigned long, unsigned long);
+
extern void __offline_isolated_pages(unsigned long, unsigned long);
extern int offline_pages(unsigned long, unsigned long, unsigned long);

===================================================================
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -180,31 +180,35 @@
return 0;
}

-
-int online_pages(unsigned long pfn, unsigned long nr_pages)
+/* Tell anyone who's interested that we're onlining some memory */
+static int notify_going_online(unsigned long pfn, unsigned long nr_pages)
{
- unsigned long flags;
- unsigned long onlined_pages = 0;
- struct zone *zone;
- int need_zonelists_rebuild = 0;
+ struct memory_notify arg;
int nid;
int ret;
- struct memory_notify arg;

arg.start_pfn = pfn;
arg.nr_pages = nr_pages;
arg.status_change_nid = -1;
-
+
nid = page_to_nid(pfn_to_page(pfn));
if (node_present_pages(nid) == 0)
arg.status_change_nid = nid;

ret = memory_notify(MEM_GOING_ONLINE, &arg);
ret = notifier_to_errno(ret);
- if (ret) {
+ if (ret)
memory_notify(MEM_CANCEL_ONLINE, &arg);
- return ret;
- }
+
+ return ret;
+}
+
+/* Grow the zone to fit the expected amount of memory being added */
+static struct zone *online_pages_zone(unsigned long pfn, unsigned long nr_pages)
+{
+ struct zone *zone;
+ unsigned long flags;
+
/*
* This doesn't need a lock to do pfn_to_page().
* The section can't be removed here because of the
@@ -215,6 +219,16 @@
grow_zone_span(zone, pfn, pfn + nr_pages);
grow_pgdat_span(zone->zone_pgdat, pfn, pfn + nr_pages);
pgdat_resize_unlock(zone->zone_pgdat, &flags);
+
+ return zone;
+}
+
+/* Mark a set of pages as online */
+unsigned long mark_pages_onlined(unsigned long pfn, unsigned long nr_pages)
+{
+ struct zone *zone = page_zone(pfn_to_page(pfn));
+ unsigned long onlined_pages = 0;
+ int need_zonelists_rebuild = 0;

/*
* If this zone is not populated, then it is not in zonelist.
@@ -240,10 +254,38 @@
vm_total_pages = nr_free_pagecache_pages();
writeback_set_ratelimit();

- if (onlined_pages)
+ if (onlined_pages) {
+ struct memory_notify arg;
+
+ arg.start_pfn = pfn; /* ? */
+ arg.nr_pages = onlined_pages;
+ arg.status_change_nid = -1; /* ? */
+
memory_notify(MEM_ONLINE, &arg);
+ }

+ return onlined_pages;
+}
+
+int prepare_online_pages(unsigned long pfn, unsigned long nr_pages)
+{
+ int ret = notify_going_online(pfn, nr_pages);
+ if (ret)
+ return ret;
+
+ online_pages_zone(pfn, nr_pages);
return 0;
+}
+
+int online_pages(unsigned long pfn, unsigned long nr_pages)
+{
+ int ret;
+
+ ret = prepare_online_pages(pfn, nr_pages);
+ if (ret == 0)
+ mark_pages_onlined(pfn, nr_pages);
+
+ return ret;
}
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */




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