From owner-freebsd-hackers@FreeBSD.ORG Wed Jul 16 07:31:48 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5C08B1065678 for ; Wed, 16 Jul 2008 07:31:48 +0000 (UTC) (envelope-from tapan.list@gmail.com) Received: from gv-out-0910.google.com (gv-out-0910.google.com [216.239.58.189]) by mx1.freebsd.org (Postfix) with ESMTP id D778B8FC20 for ; Wed, 16 Jul 2008 07:31:47 +0000 (UTC) (envelope-from tapan.list@gmail.com) Received: by gv-out-0910.google.com with SMTP id n8so897130gve.39 for ; Wed, 16 Jul 2008 00:31:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type:references; bh=jj27U8OLTdinKz+vBg3g9U9AFrBwEEIfFwlm7s0wVfo=; b=ZhYcPfvZxavlKoUZNQg+01IIY+jwKGVKPLvCyLaWOFS3TOZcBqpYMGfEv+BTYm/abO a5xsKBTLWm10CcN317c4rb/Eb0bN0w6LGqYEAyBqA0zAHTUKHcjuaVNQUfyFq8HiEw1x 6AR2isK92sKIlusW42ZHHdljvMcsp3z+wA+BE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:references; b=tDxmfxE9PlXeUBsXUVleiyYHacFoLyTAH3p+dm+EQyKmWaNtYdWeRRevRlxToe9Z5m /HB29PXNAO1VMtPXsnySHTqlUiq0fclcrIVxFA5v3r8n0XpZ5T9445pHrxh9V8DrorhP FX+y7+BRHUI5d1WVdxzbs8s4rCt1auNquCOPA= Received: by 10.103.40.5 with SMTP id s5mr577877muj.133.1216193506215; Wed, 16 Jul 2008 00:31:46 -0700 (PDT) Received: by 10.103.227.19 with HTTP; Wed, 16 Jul 2008 00:31:46 -0700 (PDT) Message-ID: <482257ad0807160031k34980a19na9895f38f125d4e0@mail.gmail.com> Date: Wed, 16 Jul 2008 13:01:46 +0530 From: "Tapan Chaudhari" To: freebsd-hackers@freebsd.org In-Reply-To: <200807151538.38285.doconnor@gsoft.com.au> MIME-Version: 1.0 References: <482257ad0807141106m679ec19frd853339637d27a2d@mail.gmail.com> <200807151302.30415.doconnor@gsoft.com.au> <482257ad0807142138j1f7b7dd8nda7de865a4616fc0@mail.gmail.com> <200807151538.38285.doconnor@gsoft.com.au> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Subject: Re: Can I change the device of the "/" mount point at boot time. X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Jul 2008 07:31:48 -0000 On Tue, Jul 15, 2008 at 11:38 AM, Daniel O'Connor wrote: > On Tue, 15 Jul 2008, Tapan Chaudhari wrote: > > Thanks Deniel for the reply. I am aware of the fact you mentioned > > and will keep in mind. > > Well what i am trying to achieve is a simple thing to write an > > interception driver to catch all the i/os going to a particular > > device, do some manipulations on it and than let it through to the > > original device. Well as you mentioned about geom, I have recently > > posted a mail on GEOM mailing list as I could not find geom doing > > interception, the discussion is still on (You can see the mails with > > subject line "Can GEOM be used to intercept the I/o calls to an > > existing mounted device?"). Any sugessuions on interception driver > > will be helpful? > > My first question would be "Why do you want to do that?" I am planning to write a block level snapshot driver. > > > > As an interception driver is not possible, for time being I am going > > towards the redirection concept which will require a reboot and > > changing the devices on the mount points. For redirection driver, I > > dont think I will need geom. I can directly create a new device. > > Rather I think it would be an overhead using geom for a virtual > > device. > > Any thoughts on both the issues? > > I think you'd have a lower overhead and much less hassle writing a GEOM > class and using that. > This sounds good. I will try using GEOM first. But if I could achieve interception, as I described earlier, I will go for that rather than redirection. > > -- > Daniel O'Connor software and network engineer > for Genesis Software - http://www.gsoft.com.au > "The nice thing about standards is that there > are so many of them to choose from." > -- Andrew Tanenbaum > GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C >