From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 23 Dec 2002 06:50:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 23 Dec 2002 06:50:13 -0500 Received: from cpe-24-221-186-48.ca.sprintbbd.net ([24.221.186.48]:1286 "HELO jose.vato.org") by vger.kernel.org with SMTP id ; Mon, 23 Dec 2002 06:50:12 -0500 From: "Tim Pepper" Date: Mon, 23 Dec 2002 03:58:16 -0800 To: Marcelo Tosatti Cc: Alan Cox , linux-kernel@vger.kernel.org Subject: ext3/jbd breaks md stacking in 2.4 Message-ID: <20021223035816.B9669@jose.vato.org> Mail-Followup-To: Tim Pepper , Marcelo Tosatti , Alan Cox , linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i X-PGP-Key: http://vato.org/~tpepper/pubkey.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I recently noticed that ext3/jbd break md stacking by making invalid assumptions about the buffer head's b_private pointer. There is a thread discussing this on the LVM mailing list at: http://linux.msede.com/lvm_mlist/archive/2002/07/0028.html Searching google and driver source it seems to me that as others have noticed this they've worked around it by keeping their own pools of buffer heads instead of simply stacking on the system buffer head. This strikes me as inefficient and just plain ugly. The ability to stack b_rdev, b_private and b_end_io is documented kernel behaviour and therefore shouldn't break in 2.4. The above link in particular is to a simple patch Andrew Morton suggested. This patch has been in -ac for quite a while, but is listed as not forwarded to Marcello (any reason Alan?). Is there any chance of getting this fix into mainline kernels? Tim -- ********************************************************* * tpepper@vato dot org * Venimus, Vidimus, * * http://www.vato.org/~tpepper * Dolavimus * *********************************************************