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 A660A6B01F0 for ; Tue, 17 Aug 2010 12:41:36 -0400 (EDT) Date: Tue, 17 Aug 2010 11:41:52 -0500 (CDT) From: Christoph Lameter Subject: Re: [RFC] [PATCH 2/4] dio: add page locking for direct I/O In-Reply-To: <20100817142144.GB18161@basil.fritz.box> Message-ID: References: <1281432464-14833-1-git-send-email-n-horiguchi@ah.jp.nec.com> <20100812075323.GA6112@spritzera.linux.bs1.fc.nec.co.jp> <20100812075941.GD6112@spritzera.linux.bs1.fc.nec.co.jp> <20100816020737.GA19531@spritzera.linux.bs1.fc.nec.co.jp> <20100817081753.GA28762@spritzera.linux.bs1.fc.nec.co.jp> <20100817142144.GB18161@basil.fritz.box> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: Jeff Moyer , Naoya Horiguchi , Andrew Morton , Mel Gorman , Wu Fengguang , Jun'ichi Nomura , linux-mm , LKML , Andrea Arcangeli List-ID: On Tue, 17 Aug 2010, Andi Kleen wrote: > On Tue, Aug 17, 2010 at 09:46:56AM -0400, Jeff Moyer wrote: > > Naoya Horiguchi writes: > > > > > BTW, from the discussion with Christoph I noticed my misunderstanding > > > about the necessity of additional page locking. It would seem that > > > without page locking there is no danger of racing between direct I/O and > > > page migration. So I retract this additional locking patch-set. > > > > OK, great! ;-) > > Well it sounds like we still may need something. It isn't good if O_DIRECT > can starve (or DoS) migration. Anything that increments a page refcount can interfere with migration and cause migration to be aborted and retried later. Not something new. There never was any guarantee that migration must succeed. -- 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