From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753498AbaJQHDx (ORCPT ); Fri, 17 Oct 2014 03:03:53 -0400 Received: from mga01.intel.com ([192.55.52.88]:40794 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753333AbaJQHC6 (ORCPT ); Fri, 17 Oct 2014 03:02:58 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,737,1406617200"; d="scan'208";a="615951919" Date: Thu, 16 Oct 2014 17:44:10 -0400 From: Matthew Wilcox To: Mathieu Desnoyers Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 12/21] vfs: Remove get_xip_mem Message-ID: <20141016214410.GH11522@wil.cx> References: <1411677218-29146-1-git-send-email-matthew.r.wilcox@intel.com> <1411677218-29146-13-git-send-email-matthew.r.wilcox@intel.com> <20141016121446.GJ19075@thinkos.etherlink> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141016121446.GJ19075@thinkos.etherlink> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16, 2014 at 02:14:46PM +0200, Mathieu Desnoyers wrote: > > +++ b/fs/open.c > > @@ -655,11 +655,8 @@ int open_check_o_direct(struct file *f) > > { > > /* NB: we're sure to have correct a_ops only after f_op->open */ > > if (f->f_flags & O_DIRECT) { > > - if (!f->f_mapping->a_ops || > > - ((!f->f_mapping->a_ops->direct_IO) && > > - (!f->f_mapping->a_ops->get_xip_mem))) { > > + if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO) > > Why is it OK to remove the check for get_xip_mem callback here, rather > than replacing it with a IS_DAX check like the rest of this patch does ? > I'm probably missing something. XIP used to intercept I/Os by having the filesystem's ->read & ->write methods call xip_file_read (/write). That would do the I/O, and so there was no need to have a ->direct_IO element in a_ops. For DAX, we use the generic VFS code to call back into the filesystem's ->direct_IO entry point, so the check above for ->direct_IO now checks for both regular and DAX support. Or to put it another way, DAX now requires that the filesystem support O_DIRECT. Which is pretty much the way it has to be anyway, since DAX is direct!