| From | Greg Kroah-Hartman <> | Subject | [ 074/120] kpageflags: fix wrong KPF_THP on non-huge compound pages | Date | Thu, 11 Oct 2012 10:00:26 +0900 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
commit 7a71932d5676b7410ab64d149bad8bde6b0d8632 upstream.
KPF_THP can be set on non-huge compound pages (like slab pages or pages allocated by drivers with __GFP_COMP) because PageTransCompound only checks PG_head and PG_tail. Obviously this is a bug and breaks user space applications which look for thp via /proc/kpageflags.
This patch rules out setting KPF_THP wrongly by additionally checking PageLRU on the head pages.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: David Rientjes <rientjes@google.com> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/proc/page.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -115,7 +115,13 @@ u64 stable_page_flags(struct page *page) u |= 1 << KPF_COMPOUND_TAIL; if (PageHuge(page)) u |= 1 << KPF_HUGE; - else if (PageTransCompound(page)) + /* + * PageTransCompound can be true for non-huge compound pages (slab + * pages or pages allocated by drivers with __GFP_COMP) because it + * just checks PG_head/PG_tail, so we need to check PageLRU to make + * sure a given page is a thp, not a non-huge compound page. + */ + else if (PageTransCompound(page) && PageLRU(compound_trans_head(page))) u |= 1 << KPF_THP; /*
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