Commit 435b405c authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

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



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: default avatarMinchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarYasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 41d575ad

include/linux/page-isolation.h

+4 −0
Original line number Diff line number Diff line
@@ -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,

mm/page_alloc.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

{

mm/page_isolation.c

+14 −2
Original line number Diff line number Diff line
@@ -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 &&

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