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memory-hotplug: fix pages missed by race rather than failing

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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.

[akpm@linux-foundation.org: small cleanup]
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2012-10-08 16:32:16 -07:00 committed by Linus Torvalds
parent 41d575ad4a
commit 435b405c06
3 changed files with 19 additions and 3 deletions
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4
include/linux/page-isolation.h
View file

@ -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,

2
mm/page_alloc.c
View file

@ -925,7 +925,7 @@ 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)
{

16
mm/page_isolation.c
View file

@ -201,8 +201,20 @@ __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;
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 &&