Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755859AbYCNIn4 (ORCPT ); Fri, 14 Mar 2008 04:43:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752153AbYCNInr (ORCPT ); Fri, 14 Mar 2008 04:43:47 -0400 Received: from mtagate5.de.ibm.com ([195.212.29.154]:39440 "EHLO mtagate5.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752053AbYCNInp (ORCPT ); Fri, 14 Mar 2008 04:43:45 -0400 Date: Fri, 14 Mar 2008 09:43:38 +0100 From: Christof Schmitt To: linux-btrace@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: blktrace/relay/s390: Oops in subbuf_splice_actor Message-ID: <20080314084337.GA9436@schmichrtp.de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2816 Lines: 55 When i first setup blktrace on a s390 z/VM guest to trace to another system and then put some load on the disk traced, the system oopses in subbuf_splice_actor. The setup is as simple as # blktrace -h tracehost -d /dev/sda # dd if=/dev/sda of=/dev/null This is the stack trace from the current 2.6.25-rc5, i added noinline to subbuf_splice_actor, otherwise it will be inlined: Unable to handle kernel pointer dereference at virtual kernel address 0000000000000000 Oops: 0004 [#1] PREEMPT SMP DEBUG_PAGEALLOC Modules linked in: binfmt_misc vmur CPU: 1 Not tainted 2.6.25-rc5 #10 Process blktrace (pid: 2655, task: 000000002bc38238, ksp: 000000002b0d79a8) Krnl PSW : 0704100180000000 00000000000874e2 (subbuf_splice_actor+0x212/0x364) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:1 PM:0 EA:3 Krnl GPRS: 0a00000000000001 000000002b2bb000 0000000000001000 00000000000000c8 0000000000001000 0000000000001000 0000000000000000 0000000000000200 0000000000019000 0000000000000019 0000000000066fd8 000000002b0d79e8 000003e040ed7938 0000000000000000 000000000008749e 000000002b0d79e8 Krnl Code: 00000000000874d4: e31050b00004 lg %r1,176(%r5) 00000000000874da: 1854 lr %r5,%r4 00000000000874dc: e3cc10000004 lg %r12,0(%r12,%r1) >00000000000874e2: e3c320000024 stg >%r12,0(%r3,%r2) 00000000000874e8: e330b2700014 lgf %r3,624(%r11) 00000000000874ee: eb330004000d sllg %r3,%r3,4 00000000000874f4: e320b2680004 lg %r2,616(%r11) 00000000000874fa: 1814 lr %r1,%r4 Call Trace: ([<000000000008749e>] subbuf_splice_actor+0x1ce/0x364) [<00000000000876a2>] relay_file_splice_read+0x6e/0xfc [<00000000000e4f90>] do_splice_to+0x9c/0xb4 [<00000000000e545c>] splice_direct_to_actor+0xd8/0x21c [<00000000000e55ec>] do_splice_direct+0x4c/0x70 [<00000000000bc2be>] do_sendfile+0x1b6/0x228 [<00000000000bc382>] sys_sendfile64+0x52/0xe4 [<00000000000241c0>] sysc_noemu+0x10/0x16 [<00000200001304da>] 0x200001304da Some debug printks show that subbuf_pages in this case is 512 and the for loop goes until spd.nr_pages is 25, before hitting the problem. I am wondering if the numbers make sense here, since spd.pages has only 16 pages allocated (with PIPE_BUFFERS). But i did not yet understand how much data this loop is supposed to assign. Does anybody have an idea what is happening here, or how to continue debugging this problem? Christof -- 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/