From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f198.google.com (mail-ot0-f198.google.com [74.125.82.198]) by kanga.kvack.org (Postfix) with ESMTP id 86C216B0008 for ; Fri, 2 Mar 2018 12:43:47 -0500 (EST) Received: by mail-ot0-f198.google.com with SMTP id w23so5599837otj.6 for ; Fri, 02 Mar 2018 09:43:47 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 62si1981060oih.104.2018.03.02.09.43.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Mar 2018 09:43:46 -0800 (PST) From: Andrea Arcangeli Subject: [PATCH 0/1] FOLL_NOWAIT and get_user_pages_unlocked Date: Fri, 2 Mar 2018 18:43:42 +0100 Message-Id: <20180302174343.5421-1-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Al Viro , "Dr. David Alan Gilbert" , qemu-devel@nongnu.org, linux-mm@kvack.org Hello, KVM is hanging on postcopy live migration. David tracked it down to commit ce53053ce378c21e7ffc45241fd67d6ee79daa2b and the problem is pretty obvious then. Either we teach get_user_pages_locked/unlocked to handle FOLL_NOWAIT (so faultin_nopage works right even when the nonblocking pointer is not NULL) or we need to revert part of commit ce53053ce378c21e7ffc45241fd67d6ee79daa2b and keep using FOLL_NOWAIT only as parameter to get_user_pages (which won't ever set nonblocking pointer to non-NULL). I suppose the former approach is preferred to be more robust. Thanks, Andrea Andrea Arcangeli (1): mm: gup: teach get_user_pages_unlocked to handle FOLL_NOWAIT mm/gup.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) -- 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