From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752792Ab0CQQ7d (ORCPT ); Wed, 17 Mar 2010 12:59:33 -0400 Received: from verein.lst.de ([213.95.11.210]:40022 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751615Ab0CQQ7b (ORCPT ); Wed, 17 Mar 2010 12:59:31 -0400 Date: Wed, 17 Mar 2010 17:58:54 +0100 From: Christoph Hellwig To: Avi Kivity Cc: Chris Webb , balbir@linux.vnet.ibm.com, KVM development list , Rik van Riel , KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Christoph Hellwig , Kevin Wolf Subject: Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter Message-ID: <20100317165854.GC29548@lst.de> References: <4B9DE635.8030208@redhat.com> <20100315080726.GB18054@balbir.in.ibm.com> <4B9DEF81.6020802@redhat.com> <20100315202353.GJ3840@arachsys.com> <4B9F4CBD.3020805@redhat.com> <20100317152452.GZ31148@arachsys.com> <4BA101C5.9040406@redhat.com> <4BA105FE.2000607@redhat.com> <20100317164752.GA31884@arachsys.com> <4BA1090E.9090502@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BA1090E.9090502@redhat.com> User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 17, 2010 at 06:53:34PM +0200, Avi Kivity wrote: > Meanwhile I looked at the code, and it looks bad. There is an > IO_CMD_FDSYNC, but it isn't tagged, so we have to drain the queue before > issuing it. In any case, qemu doesn't use it as far as I could tell, > and even if it did, device-matter doesn't implement the needed > ->aio_fsync() operation. No one implements it, and all surrounding code is dead wood. It would require us to do asynchronous pagecache operations, which involve major surgery of the VM code. Patches to do this were rejected multiple times.