From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id BF1CA6B0069 for ; Fri, 18 Nov 2011 09:04:41 -0500 (EST) Received: by wwf10 with SMTP id 10so4304965wwf.26 for ; Fri, 18 Nov 2011 06:04:37 -0800 (PST) MIME-Version: 1.0 Date: Fri, 18 Nov 2011 22:04:37 +0800 Message-ID: Subject: [PATCH] hugetlb: detect race if fail to COW From: Hillf Danton Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Andrew Morton , Michal Hocko , Johannes Weiner , linux-mm@kvack.org, LKML In the error path that we fail to allocate new huge page, before try again, we have to check race since page_table_lock is re-acquired. If racing, our job is done. Signed-off-by: Hillf Danton --- --- a/mm/hugetlb.c Fri Nov 18 21:38:30 2011 +++ b/mm/hugetlb.c Fri Nov 18 21:48:15 2011 @@ -2407,7 +2407,14 @@ retry_avoidcopy: BUG_ON(page_count(old_page) != 1); BUG_ON(huge_pte_none(pte)); spin_lock(&mm->page_table_lock); - goto retry_avoidcopy; + ptep = huge_pte_offset(mm, address & huge_page_mask(h)); + if (likely(pte_same(huge_ptep_get(ptep), pte))) + goto retry_avoidcopy; + /* + * race occurs while re-acquiring page_table_lock, and + * our job is done. + */ + return 0; } WARN_ON_ONCE(1); } -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org