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. Changelog in v4: - check PageLRU with compound_trans_head() - fix patch subject again Changelog in v3: - check PageSlab instead of PageAnon - fix patch subject Changelog in v2: - add a comment in code Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> --- fs/proc/page.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git v3.6-rc6.orig/fs/proc/page.c v3.6-rc6/fs/proc/page.c index 7fcd0d6..b8730d9 100644 --- v3.6-rc6.orig/fs/proc/page.c +++ v3.6-rc6/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; /* -- 1.7.11.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>