From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx190.postini.com [74.125.245.190]) by kanga.kvack.org (Postfix) with SMTP id E6EA26B002B for ; Wed, 26 Sep 2012 16:28:51 -0400 (EDT) From: Naoya Horiguchi Subject: [PATCH v4] kpageflags: fix wrong KPF_THP on non-huge compound pages Date: Wed, 26 Sep 2012 16:27:14 -0400 Message-Id: <1348691234-31729-1-git-send-email-n-horiguchi@ah.jp.nec.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wu Fengguang , Andrew Morton Cc: KOSAKI Motohiro , David Rientjes , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org 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 Acked-by: KOSAKI Motohiro Acked-by: David Rientjes --- 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org