From 7a71932d5676b7410ab64d149bad8bde6b0d8632 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Mon, 8 Oct 2012 16:33:47 -0700 Subject: [PATCH] kpageflags: fix wrong KPF_THP on non-huge compound pages 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 Acked-by: KOSAKI Motohiro Acked-by: David Rientjes Reviewed-by: Fengguang Wu Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/page.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/proc/page.c b/fs/proc/page.c index 7fcd0d60a96..b8730d9ebae 100644 --- 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; /*