From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f178.google.com (mail-pd0-f178.google.com [209.85.192.178]) by kanga.kvack.org (Postfix) with ESMTP id AD6DA6B0074 for ; Fri, 17 Oct 2014 03:22:53 -0400 (EDT) Received: by mail-pd0-f178.google.com with SMTP id y10so294826pdj.23 for ; Fri, 17 Oct 2014 00:22:53 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTP id fx15si319067pdb.251.2014.10.17.00.22.52 for ; Fri, 17 Oct 2014 00:22:52 -0700 (PDT) Date: Thu, 16 Oct 2014 18:33:31 -0400 From: Matthew Wilcox Subject: Re: [PATCH v11 07/21] dax,ext2: Replace XIP read and write with DAX I/O Message-ID: <20141016223331.GA11169@wil.cx> References: <1411677218-29146-1-git-send-email-matthew.r.wilcox@intel.com> <1411677218-29146-8-git-send-email-matthew.r.wilcox@intel.com> <20141016095027.GE19075@thinkos.etherlink> <20141016195112.GE11522@wil.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141016195112.GE11522@wil.cx> Sender: owner-linux-mm@kvack.org List-ID: To: Mathieu Desnoyers Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Oct 16, 2014 at 03:51:12PM -0400, Matthew Wilcox wrote: > On Thu, Oct 16, 2014 at 11:50:27AM +0200, Mathieu Desnoyers wrote: > > > + if (rw == WRITE) { > > > + if (!buffer_mapped(bh)) { > > > + retval = -EIO; > > > + /* FIXME: fall back to buffered I/O */ > > > > Fallback on buffered I/O would void guarantee about having data stored > > into persistent memory after write returns. Not sure we actually want > > that. > > Yeah, I think that comment is just stale. I can't see a way in which > buffered I/O would succeed after DAX I/O falis. On further consideration, I think the whole thing is just foolish. I don't see how get_block(create == 1) can return success *and* a buffer that is !mapped. So I did this nice simplification: - if (rw == WRITE) { - if (!buffer_mapped(bh)) { - retval = -EIO; - /* FIXME: fall back to buffered I/O */ - break; - } - hole = false; - } else { - hole = !buffer_written(bh); - } + hole = (rw != WRITE) && !buffer_written(bh); (compile-tested only; I'm going to run all the changes through xfstests next week when I'm back home before sending out a v12). -- 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