From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: direct_access, pinning and truncation Date: Thu, 9 Oct 2014 12:10:38 +1100 Message-ID: <20141009011038.GA4376@dastard> References: <20141008190523.GM5098@wil.cx> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org To: Matthew Wilcox Return-path: Received: from ipmail06.adl6.internode.on.net ([150.101.137.145]:28645 "EHLO ipmail06.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751347AbaJIBKm (ORCPT ); Wed, 8 Oct 2014 21:10:42 -0400 Content-Disposition: inline In-Reply-To: <20141008190523.GM5098@wil.cx> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Oct 08, 2014 at 03:05:23PM -0400, Matthew Wilcox wrote: > > One of the things on my todo list is making O_DIRECT work to a > memory-mapped direct_access file. I don't understand the motivation or the use case: O_DIRECT is purely for bypassing the page cache, and DAX already bypasses the page cache. What difference is there between the DAX read/write path and a DAX-based O_DIRECT IO path, and why doesn't just ignoring O_DIRECT for DAX enabled filesystems simply do what you need? Cheers, Dave. -- Dave Chinner david@fromorbit.com