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 <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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 7fcd0d6..b8730d9 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -115,7 +115,13 @@
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;
/*