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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: 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>
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parent
41d575ad4a
commit
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3 changed files with 19 additions and 3 deletions
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@ -6,6 +6,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count);
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void set_pageblock_migratetype(struct page *page, int migratetype);
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int move_freepages_block(struct zone *zone, struct page *page,
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int migratetype);
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int move_freepages(struct zone *zone,
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struct page *start_page, struct page *end_page,
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int migratetype);
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/*
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* Changes migrate type in [start_pfn, end_pfn) to be MIGRATE_ISOLATE.
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* If specified range includes migrate types other than MOVABLE or CMA,
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@ -925,7 +925,7 @@ static int fallbacks[MIGRATE_TYPES][4] = {
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* Note that start_page and end_pages are not aligned on a pageblock
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* boundary. If alignment is required, use move_freepages_block()
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*/
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static int move_freepages(struct zone *zone,
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int move_freepages(struct zone *zone,
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struct page *start_page, struct page *end_page,
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int migratetype)
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{
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@ -201,8 +201,20 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn)
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}
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page = pfn_to_page(pfn);
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if (PageBuddy(page)) {
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if (get_freepage_migratetype(page) != MIGRATE_ISOLATE)
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break;
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/*
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* If race between isolatation and allocation happens,
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* some free pages could be in MIGRATE_MOVABLE list
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* although pageblock's migratation type of the page
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* is MIGRATE_ISOLATE. Catch it and move the page into
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* MIGRATE_ISOLATE list.
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*/
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if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
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struct page *end_page;
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end_page = page + (1 << page_order(page)) - 1;
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move_freepages(page_zone(page), page, end_page,
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MIGRATE_ISOLATE);
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}
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pfn += 1 << page_order(page);
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}
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else if (page_count(page) == 0 &&
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