kpageflags: fix wrong KPF_THP on non-huge compound pages

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 <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Acked-by: David Rientjes <[email protected]>
Reviewed-by: Fengguang Wu <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>