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authorMinchan Kim <minchan@kernel.org>2012-07-31 16:42:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-31 18:42:42 -0700
commit97d255c816946388bab504122937730d3447c612 (patch)
tree828927fe44ebb6c0bd6cfd2a0da36b68ed45b4ba
parentde34d965a80d0f61a354bdefa0b15a88bcff2028 (diff)
downloadop-kernel-dev-97d255c816946388bab504122937730d3447c612.zip
op-kernel-dev-97d255c816946388bab504122937730d3447c612.tar.gz
mm: do not use page_count() without a page pin
d179e84ba ("mm: vmscan: do not use page_count without a page pin") fixed this problem in vmscan.c but same problem is in __count_immobile_pages(). 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." Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Wanpeng Li <liwp.linux@gmail.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1874752..bb790f5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5500,11 +5500,18 @@ __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++;
/*
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