Messages in this thread | | | Date | Fri, 7 Sep 2012 12:52:30 +0900 | From | Yasuaki Ishimatsu <> | Subject | Re: [PATCH v3 3/4] memory-hotplug: bug fix race between isolation and allocation |
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2012/09/07 9:39, Minchan Kim wrote: > Like below, memory-hotplug makes race between page-isolation > and page-allocation so it can hit BUG_ON in __offline_isolated_pages. > > CPU A CPU B > > start_isolate_page_range > set_migratetype_isolate > spin_lock_irqsave(zone->lock) > > free_hot_cold_page(Page A) > /* without zone->lock */ > migratetype = get_pageblock_migratetype(Page A); > /* > * Page could be moved into MIGRATE_MOVABLE > * of per_cpu_pages > */ > list_add_tail(&page->lru, &pcp->lists[migratetype]); > > set_pageblock_isolate > move_freepages_block > drain_all_pages > > /* Page A could be in MIGRATE_MOVABLE of free_list. */ > > check_pages_isolated > __test_page_isolated_in_pageblock > /* > * We can't catch freed page which > * is free_list[MIGRATE_MOVABLE] > */ > if (PageBuddy(page A)) > pfn += 1 << page_order(page A); > > /* So, Page A could be allocated */ > > __offline_isolated_pages > /* > * BUG_ON hit or offline page > * which is used by someone > */ > BUG_ON(!PageBuddy(page A)); > > This patch checks page's migratetype in freelist in __test_page_isolated_in_pageblock. > So now __test_page_isolated_in_pageblock can check the page caused by above race and > can fail of memory offlining. > > * from v2 > * Add Acked-by of Kame > > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Thanks, Yasuaki Ishimatsu
> --- > mm/page_isolation.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 87a7929..7ba7405 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -193,8 +193,11 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn) > continue; > } > page = pfn_to_page(pfn); > - if (PageBuddy(page)) > + if (PageBuddy(page)) { > + if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) > + break; > pfn += 1 << page_order(page); > + } > else if (page_count(page) == 0 && > get_freepage_migratetype(page) == MIGRATE_ISOLATE) > pfn += 1; >
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