[PATCH 1/3] mem-hotplug: call isolate_lru_page with elevated refcount

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

isolate_lru_page() must be called only with stable reference to page.
So, let's grab normal page reference.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
---
 mm/memory_hotplug.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9ca1d60..0a19109 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -705,7 +705,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		if (!pfn_valid(pfn))
 			continue;
 		page = pfn_to_page(pfn);
-		if (!page_count(page))
+		if (!get_page_unless_zero(page))
 			continue;
 		/*
 		 * We can skip free pages. And we can only deal with pages on
@@ -713,6 +713,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		 */
 		ret = isolate_lru_page(page);
 		if (!ret) { /* Success */
+			put_page(page);
 			list_add_tail(&page->lru, &source);
 			move_pages--;
 			inc_zone_page_state(page, NR_ISOLATED_ANON +
@@ -724,6 +725,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			       pfn);
 			dump_page(page);
 #endif
+			put_page(page);
 			/* Because we don't have big zone->lock. we should
 			   check this again here. */
 			if (page_count(page)) {

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