From owner-freebsd-current@FreeBSD.ORG Wed Oct 31 18:54:13 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 E787116A418 for ; Wed, 31 Oct 2007 18:54:13 +0000 (UTC) (envelope-from matrix@itlegion.ru) Received: from corpmail.itlegion.ru (corpmail.itlegion.ru [84.21.226.211]) by mx1.freebsd.org (Postfix) with SMTP id 37E5E13C4A6 for ; Wed, 31 Oct 2007 18:54:12 +0000 (UTC) (envelope-from matrix@itlegion.ru) Received: (qmail 3213 invoked from network); 31 Oct 2007 21:53:34 +0300 Received: from unknown (HELO Artem) (192.168.0.12) by 84.21.226.211 with SMTP; 31 Oct 2007 21:53:34 +0300 X-AntiVirus: Checked by Dr.Web [version: 4.44, engine: 4.44.0.09170, virus records: 253097, updated: 31.10.2007] Message-ID: <001a01c81bef$54496910$0c00a8c0@Artem> From: "Artem Kuchin" To: "Scott Long" References: <0fbb01c81be1$37e698f0$0c00a8c0@Artem> <4728B991.4020000@samsco.org> Date: Wed, 31 Oct 2007 21:39:49 +0300 Organization: IT Legion MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="ISO-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 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 18:54:14 -0000 Scott Long wrote: > 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. How is this possible? [QUOTE:] URL:http://unix.derkeiler.com/Mailing-Lists/FreeBSD/current/2006-08/msg00179.html DATE SOURCE: AUGUST 2006 freebsd-current maillis) WHO: Pawel Jakub Dawidek Unfortunately I'm not able to implement BIO_FLUSH to all out storage drivers. Currently BIO_FLUSH is supported by ata(4) (/dev/a[dr]X), da(4) and amr(4). That's the theory. I'm using standard SCSI commands for this. From the tests we made it seems that it works ok with twa(4)/twe(4). I'd still be glad if someone with SCSI/CAM foo could look at the code. [ENDQUOTE] So what changed since then? -- Artem