If race between allocation and isolation in memory-hotplug offline
happens, some pages could be in MIGRATE_MOVABLE of free_list although
the pageblock's migratetype of the page is MIGRATE_ISOLATE.
The race could be detected by get_freepage_migratetype
in __test_page_isolated_in_pageblock. If it is detected, now EBUSY
gets bubbled all the way up and the hotplug operations fails.
But better idea is instead of returning and failing memory-hotremove,
move the free page to the correct list at the time it is detected.
It could enhance memory-hotremove operation success ratio although
the race is really rare.
Suggested-by: Mel Gorman <mgor...@suse.de>
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
include/linux/page-isolation.h | 4 ++++
mm/page_alloc.c | 2 +-
mm/page_isolation.c | 15 +++++++++++++--
3 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 105077a..fca8c0a 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -6,6 +6,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page,
int count);
void set_pageblock_migratetype(struct page *page, int migratetype);
int move_freepages_block(struct zone *zone, struct page *page,
int migratetype);
+int move_freepages(struct zone *zone,
+ struct page *start_page, struct page *end_page,
+ int migratetype);
+
/*
* Changes migrate type in [start_pfn, end_pfn) to be MIGRATE_ISOLATE.
* If specified range includes migrate types other than MOVABLE or CMA,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8531fa3..5a4c4d8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -918,7 +918,7 @@ static int fallbacks[MIGRATE_TYPES][4] = {
* Note that start_page and end_pages are not aligned on a pageblock
* boundary. If alignment is required, use move_freepages_block()
*/
-static int move_freepages(struct zone *zone,
+int move_freepages(struct zone *zone,
struct page *start_page, struct page *end_page,
int migratetype)
{
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 7ba7405..a42fa8d 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -194,8 +194,19 @@ __test_page_isolated_in_pageblock(unsigned long pfn,
unsigned long end_pfn)
}
page = pfn_to_page(pfn);
if (PageBuddy(page)) {
- if (get_freepage_migratetype(page) != MIGRATE_ISOLATE)
- break;
+ /*
+ * If race between isolatation and allocation happens,
+ * some free pages could be in MIGRATE_MOVABLE list
+ * although pageblock's migratation type of the page
+ * is MIGRATE_ISOLATE. Catch it and move the page into
+ * MIGRATE_ISOLATE list.
+ */
+ if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
+ struct page *end_page = page +
+ (1 << page_order(page)) - 1;
+ move_freepages(page_zone(page), page, end_page,
+ MIGRATE_ISOLATE);
+ }
pfn += 1 << page_order(page);
}
else if (page_count(page) == 0 &&
--
1.7.9.5
--
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