Bug 524040

Summary:	block device cannot be detached from DomU
Product:	Red Hat Enterprise Linux 6	Reporter:	Andrew Jones <drjones>
Component:	kernel	Assignee:	Andrew Jones <drjones>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Martin Jenner <mjenner>
Severity:	medium	Docs Contact:
Priority:	low
Version:	6.1	CC:	jane.lv, jvillalo, luyu, pbonzini, xen-maint
Target Milestone:	rc
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	524039	Environment:
Last Closed:	2010-06-17 12:07:38 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	524039
Bug Blocks:

Description Andrew Jones 2009-09-17 16:48:26 UTC

+++ This bug was initially created as a clone of Bug #524039 +++

Description of problem:

On a PV DomU with 2.6.31-12.fc12.x86_64 detaching a block device fails, dumping a backtrace to the console.

How reproducible:

100%

Steps to Reproduce:

On Dom0

dd if=/dev/zero of=/var/lib/xen/images/disk1.dsk bs=1 count=1 seek=10G
virsh attach-disk rawhide --driver file /var/lib/xen/images/disk1.dsk xvdb

Attach will complete successfully and from DomU the new device can be seen and used without any problem.

virsh detach-disk rawhide xvdb

Actual results:

Detach appears to complete successfully from Dom0, but a stack backtrace is dumped to DomU's console and the device is only partially removed.

Expected results:

Device is completely removed without failure.

Additional info:

The backtrace

general protection fault: 0000 [#1] SMP
last sysfs file: /sys/devices/vbd-51728/block/xvdb/size
CPU 0
Modules linked in: nfsd lockd nfs_acl auth_rpcgss exportfs sunrpc ip6t_REJECT nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 dm_multipath uinput joydev xen_netfront xen_blkfront [last unloaded: microcode]
Pid: 11, comm: xenwatch Tainted: G        W  2.6.31-12.fc12.x86_64 #1
RIP: e030:[<ffffffff812136eb>]  [<ffffffff812136eb>] debugfs_remove+0x27/0x90
RSP: e02b:ffff88007d461bf0  EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffff8800041fb850 RCX: 00000000001a0006
RDX: 0000000000000000 RSI: ffffea000321bfa8 RDI: 6b6b6b6b6b6b6b6b
RBP: ffff88007d461c10 R08: 0000000000000000 R09: 00000000e027cfb5
R10: ffffffff81678e0f R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b
R13: ffff88007d461c80 R14: ffff8800798d5520 R15: ffffffffa0005048
FS:  00007f9f6266e7c0(0000) GS:ffffc90000000000(0000) knlGS:0000000000000000
CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007f97099ac000 CR3: 000000007b978000 CR4: 0000000000002620
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000000
Process xenwatch (pid: 11, threadinfo ffff88007d460000, task ffff88007d4524a0)
Stack:
 ffff88007d461c30 00000000e027cfb5 ffff8800041fb850 0000000000000000
<0> ffff88007d461c40 ffffffff811126bf ffff88007d461c40 00000000e027cfb5
<0> ffff88007d461c70 ffff88007ad3c480 ffff88007d461c70 ffffffff8126ad2c
Call Trace:
 [<ffffffff811126bf>] bdi_unregister+0x36/0x74
 [<ffffffff8126ad2c>] unlink_gendisk+0x43/0x75
 [<ffffffff811a537b>] del_gendisk+0x9e/0x10d
 [<ffffffffa000134a>] blkfront_closing+0xad/0x105 [xen_blkfront]
 [<ffffffffa00017ef>] backend_changed+0x44d/0x52e [xen_blkfront]
 [<ffffffff8100ec42>] ? check_events+0x12/0x20
 [<ffffffff8130fa30>] otherend_changed+0xf3/0x194
 [<ffffffff8100ec2f>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffff8130e52d>] xenwatch_thread+0x119/0x160
 [<ffffffff81081487>] ? autoremove_wake_function+0x0/0x5f
 [<ffffffff8130e414>] ? xenwatch_thread+0x0/0x160
 [<ffffffff81081034>] kthread+0xac/0xb4
 [<ffffffff8101312a>] child_rip+0xa/0x20
 [<ffffffff81012a90>] ? restore_args+0x0/0x30
 [<ffffffff81013120>] ? child_rip+0x0/0x20
Code: 41 5e c9 c3 55 48 89 e5 41 54 53 48 83 ec 10 0f 1f 44 00 00 65 48 8b 04 25 28 00 00 00 48 89 45 e8 31 c0 48 85 ff 49 89 fc 74 4e <48> 8b 5f 68 48 85 db 74 45 48 8b 7b 50 48 85 ff 74 3c 48 81 c7
RIP  [<ffffffff812136eb>] debugfs_remove+0x27/0x90
 RSP <ffff88007d461bf0>
---[ end trace a7919e7f17c0a729 ]---

Comment 2 RHEL Program Management 2009-09-17 17:28:41 UTC

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.

Comment 3 Andrew Jones 2010-02-24 11:47:18 UTC

Retesting with latest bits shows that this is working now. We should try to identify what fixed it though, and since what revision.

Comment 4 Andrew Jones 2010-06-17 12:07:38 UTC

This has been working quite stabling for a while now. Will close this out as current release. We can reopen as 6.1 work if we need to learn more about it later.