From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765222AbXGYMyR (ORCPT ); Wed, 25 Jul 2007 08:54:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759695AbXGYMyG (ORCPT ); Wed, 25 Jul 2007 08:54:06 -0400 Received: from knopper.net ([85.214.68.145]:40300 "EHLO knopper.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758637AbXGYMyF (ORCPT ); Wed, 25 Jul 2007 08:54:05 -0400 X-Greylist: delayed 1434 seconds by postgrey-1.27 at vger.kernel.org; Wed, 25 Jul 2007 08:54:05 EDT Date: Wed, 25 Jul 2007 14:36:53 +0200 From: Klaus Knopper To: linux-kernel@vger.kernel.org Subject: PROBLEM: kernel 2.6.22 do_generic_mapping_read() hangs for no apparent reason Message-ID: <20070725123653.GP5357@knopper.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Organization: Knopper Networks User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, Sorry about the quite poor subject. I just got stuck in the debugging and cannot point to the exact location of the problem, though I am quite sure it's a kernel 2.6.22 problem, and not a "third-party-module" problem. cloop-2.06 (block device module similar to loop.c) uses do_generic_file_read(), which is translated to do_generic_mapping_read() in mm/filemap.c, which worked fine up to and including Kernel 2.6.21.6. In Kernel 2.6.22, do_generic_file_read() blocks indefinitely with no log message at all, whenever data is read from the file and the read_actor is NOT called (i.e. parts of the file-to-be-read are probably already cached somewhere). Unfortunately, apart from cloop, there seem to be not many drivers that still use do_generic_file_read, so maybe it's time for a rewrite anyways. If anybody would volunteer to help debugging or rewriting cloop to work with Kernels >= 2.6.22, a lot of people developing live CDs would be very happy (including me. ;-) cloop source code is at http://debian-knoppix.alioth.debian.org/sources/cloop_2.06-2.tar.gz (make cloop.ko KERNEL_DIR=/path/to/kernel/source) With kind regards -Klaus Knopper