3.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Naoya Horiguchi <n-horigu...@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-horigu...@ah.jp.nec.com>
Acked-by: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com>
Acked-by: David Rientjes <rient...@google.com>
Reviewed-by: Fengguang Wu <fengguang...@intel.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@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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