From owner-freebsd-current@FreeBSD.ORG Wed Oct 31 17:34:22 2007 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0498416A421 for ; Wed, 31 Oct 2007 17:34:22 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.freebsd.org (Postfix) with ESMTP id AFADB13C447 for ; Wed, 31 Oct 2007 17:34:21 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from phobos.samsco.home (phobos.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.13.8/8.13.8) with ESMTP id l9VHLhur005412; Wed, 31 Oct 2007 11:21:43 -0600 (MDT) (envelope-from scottl@samsco.org) Message-ID: <4728B991.4020000@samsco.org> Date: Wed, 31 Oct 2007 11:21:21 -0600 From: Scott Long User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.6) Gecko/20070802 SeaMonkey/1.1.4 MIME-Version: 1.0 To: Artem Kuchin References: <0fbb01c81be1$37e698f0$0c00a8c0@Artem> In-Reply-To: <0fbb01c81be1$37e698f0$0c00a8c0@Artem> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (pooker.samsco.org [168.103.85.57]); Wed, 31 Oct 2007 11:21:43 -0600 (MDT) X-Spam-Status: No, score=-1.4 required=5.5 tests=ALL_TRUSTED autolearn=failed version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on pooker.samsco.org Cc: freebsd-current@freebsd.org Subject: Re: BIO_FLUSH on twe driver. Why is it not there? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Oct 2007 17:34:22 -0000 Artem Kuchin wrote: > 7-BETA1 > gjournal complained that BIO_FLUSH is not supported by the driver. That > is twe driver. > However, twe is working via scsi subsystem and the authour of gjournal > said somewhere that he > has had implemeneted BIO_FLISH for scsi and he specifically mentioned > that he has tested twe and twa and they both support BIO_FLUSH. > Then why BIO_FLISH is not supported now? > The twe driver does NOT operate under the SCSI subsystem. As for flush semantics in SCSI, they are much better done with ordered tags, not explicit SYNC_CACHE commands. That's not to say that SYNC_CACHE won't work (well, except for random devices that will hang with it in unpredictable ways, but no one seems to care about that little detail). Unfortunately, BIO_ORDERED was removed from the FreeBSD block layer several years ago. Scott