Missing Bartlomiej, Sorry! On 06/14/2012 10:12 AM, Minchan Kim wrote: > d179e84ba fixed the problem[1] in vmscan.c but same problem is here. > Let's fix it. > > [1] http://comments.gmane.org/gmane.linux.kernel.mm/65844 > > I copy and paste d179e84ba's contents for description. > > "It is unsafe to run page_count during the physical pfn scan because > compound_head could trip on a dangling pointer when reading > page->first_page if the compound page is being freed by another CPU." > > * changelog from v1 > - Add comment about skip tail page of THP - Andrea > - fix typo - Wanpeng Li > - based on next-20120613 > > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxx> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Cc: Wanpeng Li <liwp.linux@xxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > --- > mm/page_alloc.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 266f267..543cc2d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5496,11 +5496,18 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count) > continue; > > page = pfn_to_page(check); > - if (!page_count(page)) { > + /* > + * We can't use page_count without pin a page > + * because another CPU can free compound page. > + * This check already skips compound tails of THP > + * because their page->_count is zero at all time. > + */ > + if (!atomic_read(&page->_count)) { > if (PageBuddy(page)) > iter += (1 << page_order(page)) - 1; > continue; > } > + > if (!PageLRU(page)) > found++; > /* -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>