Re: dm-snapshot

From: sdrb <sdrb@onet.eu>
To: device-mapper development <dm-devel@redhat.com>
Subject: Re: dm-snapshot
Date: Thu, 29 Jan 2009 11:44:44 +0100	[thread overview]
Message-ID: <4981889C.5000607@onet.eu> (raw)
In-Reply-To: <Pine.LNX.4.64.0901271601180.3884@hs20-bc2-1.build.redhat.com>

Hi,

Ok -  is it possible to tell which commits on git.kernel.org are fixing it?

Mikulas Patocka wrote:
> Hi
> 
> Upgrade to 2.6.28.* It is already fixed there.
> 
> Mikulas
> 
> On Tue, 27 Jan 2009, sdrb wrote:
> 
>> Hello,
>>
>> I've been using snapshots functionality from DM for some time and sometimes I
>> encounter following calltrace:
>>
>> -------------
>> Pid: 26230, comm: kcopyd Not tainted (2.6.27.6 #36)
>> EIP: 0060:[<c044d485>] EFLAGS: 00010282 CPU: 1
>> EIP is at remove_exception+0x5/0x20
>> EAX: ca3b5908 EBX: ca3b5908 ECX: 00200200 EDX: 00100100
>> ESI: f7b489f8 EDI: e92ad980 EBP: 00000000 ESP: f29c7ec0
>> DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
>> Process kcopyd (pid: 26230, ti=f29c6000 task=e8512430 task.ti=f29c6000)
>> Stack: c044e03f 0000000d 00000000 c85948c0 00000000 c044f2e7 0009bc30 00000000
>>       0000e705 00000000 e8e41288 e92ad980 00000000 c044e0f0 e8e41288 c7800ec8
>>       00000000 c0449224 00000000 c7800fb4 00000400 00000000 00000000 f2bdfbb0
>> Call Trace:
>> [<c044e03f>] pending_complete+0x9f/0x110
>> [<c044f2e7>] persistent_commit+0xc7/0x1100x110
>> [<c044e0f0>] copy_callback+0x30/0x40
>> [<c0449224>] segment_complete+0x154/0x1d0
>> [<c0448e55>] run_complete_job+0x45/0x80
>> [<c04490d0>] segment_complete+0x0/0x1d0
>> [<c0448e10>] run_complete_job+0x0/0x80
>> [<c0449014>] process_jobs+0x14/0x70
>> [<c0449070>] do_work+0x0/0x40
>> [<c0449086>] do_work+0x16/0x40
>> [<c013502d>] run_workqueue+0x4d/0xf0
>> [<c013514d>] worker_thread+0x7d/0xc0
>> [<c01382e0>] autoremove_wake_function+0x0/0x30
>> [<c0526583>] __sched_text_start+0x1e3/0x4a0
>> [<c01382e0>] autoremove_wake_function+0x0/0x30
>> [<c0121a2b>] complete+0x2b/0x40
>> [<c01350d0>] worker_thread+0x0/0xc0
>> [<c0137db4>] kthread+0x44/0x70
>> [<c0137d70>] kthread+0x0/0x70
>> [<c0104c57>] kernel_thread_helper+0x7/0x10
>> =======================
>> Code: 4b 0c e8 cf ff ff ff 8b 56 08 8d 04 c2 8b 10 89 13 89 18 89 5a 04
>> 89 43 04 5b 5e c3 8d 76 00 8d bc 27 00 00 00 00 8b 48 04 8b 10 <89> 11
>> 89 4a 04 c7 00 00 01 10 00 c7 40 04 00 02 20 00 c3 90 8d
>> EIP: [<c044d485>] remove_exception+0x5/0x20 SS:ESP 0068:f29c7ec0
>> --------------
>>
>> As I see it occurs because kernel tried to access poisoned element list.
>> Isn't it because of given element has been deleted from list earlier and
>> now kernel is trying to delete it second time? I had similar problems, when
>> I deleted (by mistake) element from list which was the "head" of list. In
>> other words
>> - I had the pointer to the head element of list and I removed this element
>> from list, so
>> this pointer points to element outside the list. Then I tried to go through
>> this list using
>> this pointer as a head of list - and then I get similar error. In fact I lost
>> contact with this
>> list because I didn't change pointer to another element in that list before I
>> deleted head element.
>>
>> Aren't the both situations (calltrace and mine) similar?
>>
>> p.s. It is probably the same problem as in:
>> https://www.redhat.com/archives/dm-devel/2008-December/msg00006.html
>>
>> --
>> dm-devel mailing list
>> dm-devel@redhat.com
>> https://www.redhat.com/mailman/listinfo/dm-devel
>>
> 
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