From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 247736B01EE for ; Thu, 1 Apr 2010 03:41:26 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o317fMJv011726 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Thu, 1 Apr 2010 16:41:22 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 6877C45DE50 for ; Thu, 1 Apr 2010 16:41:22 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 4842A45DE4E for ; Thu, 1 Apr 2010 16:41:22 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 293E5E38001 for ; Thu, 1 Apr 2010 16:41:22 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id C89B6EF8027 for ; Thu, 1 Apr 2010 16:41:21 +0900 (JST) From: KOSAKI Motohiro Subject: [LSF/MM TOPIC][ATTEND] How to fix direct-io vs fork issue Message-Id: <20100401154419.BE4C.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Thu, 1 Apr 2010 16:41:21 +0900 (JST) Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org, lsf10-pc@lists.linuxfoundation.org Cc: kosaki.motohiro@jp.fujitsu.com, Nick Piggin List-ID: Hi I would like to ask about one difficult problem about people. currently, direct-io implementation has big sick about VM interaction. it assume get_user_pages() can pin the target pages in page's mm. but it doesn't. fork and cow might replace the relationship between task's mm and pages. therefore cuncurrent directio and fork can corrupt the process's data. There was two proposal in past day. 1) introduce new page flags 2) introduce new lock. unfortunately both proposal got strong complaint from other developers. then, we still have this issue. I don't have clever idea. I hope discuss how to fix or give it up. thanks to linus. his recent read_pagemap discussion restre my memory that I need post this mail. -- 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