Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756588AbXLOF63 (ORCPT ); Sat, 15 Dec 2007 00:58:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751636AbXLOF6S (ORCPT ); Sat, 15 Dec 2007 00:58:18 -0500 Received: from waste.org ([66.93.16.53]:48826 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750800AbXLOF6R (ORCPT ); Sat, 15 Dec 2007 00:58:17 -0500 Date: Fri, 14 Dec 2007 23:55:50 -0600 From: Matt Mackall To: Andrew Morton Cc: Mel Gorman , James Bottomley , jens.axboe@oracle.com, liml@rtr.ca, lkml@rtr.ca, matthew@wil.cx, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org Subject: Re: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Message-ID: <20071215055550.GN19691@waste.org> References: <47618B0B.8020203@rtr.ca> <20071213195350.GH10104@kernel.dk> <20071213200219.GI10104@kernel.dk> <476190BE.9010405@rtr.ca> <20071213200958.GK10104@kernel.dk> <20071213140207.111f94e2.akpm@linux-foundation.org> <1197584106.3154.55.camel@localhost.localdomain> <20071213142935.47ff19d9.akpm@linux-foundation.org> <20071215010940.GB28613@csn.ul.ie> <20071214180206.e0325503.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071214180206.e0325503.akpm@linux-foundation.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2625 Lines: 55 On Fri, Dec 14, 2007 at 06:02:06PM -0800, Andrew Morton wrote: > On Sat, 15 Dec 2007 01:09:41 +0000 Mel Gorman wrote: > > > On (13/12/07 14:29), Andrew Morton didst pronounce: > > > > The simple way seems to be to malloc a large area, touch every page and > > > > then look at the physical pages assigned ... they now mostly seem to be > > > > descending in physical address. > > > > > > > > > > OIC. -mm's /proc/pid/pagemap can be used to get the pfn's... > > > > > > > I tried using pagemap to verify the patch but it triggered BUG_ON > > checks. Perhaps I am using the interface wrong but I would still not > > expect it to break in this fashion. I tried 2.6.24-rc4-mm1, 2.6.24-rc5-mm1, > > 2.6.24-rc5 with just the maps4 patches applied and 2.6.23 with maps4 patches > > applied. Each time I get errors like this; > > > > [ 90.108315] BUG: sleeping function called from invalid context at include/asm/uaccess_32.h:457 > > [ 90.211227] in_atomic():1, irqs_disabled():0 > > [ 90.262251] no locks held by showcontiguous/2814. > > [ 90.318475] Pid: 2814, comm: showcontiguous Not tainted 2.6.24-rc5 #1 > > [ 90.395344] [] show_trace_log_lvl+0x1a/0x30 > > [ 90.456948] [] show_trace+0x12/0x20 > > [ 90.510173] [] dump_stack+0x6e/0x80 > > [ 90.563409] [] __might_sleep+0xc3/0xe0 > > [ 90.619765] [] copy_to_user+0x3d/0x60 > > [ 90.675153] [] add_to_pagemap+0x5c/0x80 > > [ 90.732513] [] pagemap_pte_range+0x68/0xb0 > > [ 90.793010] [] walk_page_range+0x112/0x210 > > [ 90.853482] [] pagemap_read+0x176/0x220 > > [ 90.910863] [] vfs_read+0x94/0x150 > > [ 90.963058] [] sys_read+0x3d/0x70 > > [ 91.014219] [] syscall_call+0x7/0xb > > > > ... > > > > Just using cp to read the file is enough to cause problems but I included > > a very basic program below that produces the BUG_ON checks. Is this a known > > issue or am I using the interface incorrectly? > > I'd say you're using it correctly but you've found a hitherto unknown bug. > On i386 highmem machines with CONFIG_HIGHPTE (at least) pte_offset_map() > takes kmap_atomic(), so pagemap_pte_range() can't do copy_to_user() as it > presently does. Damn, I coulda sworn I fixed that. -- Mathematics is the supreme nostalgia of our time. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/