Re: Calltrace in dm-snapshot in 2.6.27 kernel

["aluno3@poczta.onet.pl" <aluno3@poczta.onet.pl>]

Hi 

I tested kernel 2.6.27.6 with patch from 2.6.28rc (wait for chunks in destructor,fix register_snapshot deadlock,) and I identified next problem with kernel and dm but repeatability this problem is very small.I got call trace:


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+0xc7/0x110
[<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
---[ end trace 834a1d3742a1be05 ]---



addr2line returned include/linux/list.h:93 for EIP c044d485:


static inline void __list_del(struct list_head * prev, struct list_head
* next)
{
        next->prev = prev;
        prev->next = next;      //line 93
}




A few weeks ago I got similar call trace with plain kernel 2.6.27 and
patches from mail thread:


BUG: unable to handle kernel paging request at 00200200
IP: [<c044bf65>] remove_exception+0x5/0x20
*pdpt = 0000000029acc001 *pde = 0000000000000000
Oops: 0002 [#1] SMP
Modules linked in: iscsi_trgt mptctl mptbase st sg drbd bonding
iscsi_tcp libiscsi scsi_transport_iscsi aacraid sata_nv forcedeth button
ftdi_sio usbserial

Pid: 31375, comm: kcopyd Not tainted (2.6.27 #21)
EIP: 0060:[<c044bf65>] EFLAGS: 00010282 CPU: 1
EIP is at remove_exception+0x5/0x20
EAX: f276da88 EBX: f276da88 ECX: 00200200 EDX: 00100100
ESI: c79a4a58 EDI: c9268cc0 EBP: 00000000 ESP: ecbcbec0
 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
Process kcopyd (pid: 31375, ti=ecbca000 task=e6d9d220 task.ti=ecbca000)
Stack: c044cb1f 0000000e 00000000 c916b480 00000000 c044dde3 00018f47
00000000
       00002870 00000000 c70cba48 c9268cc0 00000000 c044cbd0 c70cba48
c720aec8
       00000000 c0447d04 00000000 c720afb4 00000400 00000000 00000000
efc65580
Call Trace:
 [<c044cb1f>] pending_complete+0x9f/0x110
 [<c044dde3>] persistent_commit+0xe3/0x110
 [<c044cbd0>] copy_callback+0x30/0x40
 [<c0447d04>] segment_complete+0x154/0x1d0
 [<c0447935>] run_complete_job+0x45/0x80
 [<c0447bb0>] segment_complete+0x0/0x1d0
 [<c04478f0>] run_complete_job+0x0/0x80
 [<c0447af4>] process_jobs+0x14/0x70
 [<c0447b50>] do_work+0x0/0x40
 [<c0447b66>] do_work+0x16/0x40
 [<c013509d>] run_workqueue+0x4d/0xf0
 [<c01351bd>] worker_thread+0x7d/0xc0
 [<c0138350>] autoremove_wake_function+0x0/0x30
 [<c0524f2c>] __sched_text_start+0x1ec/0x4b0
 [<c0138350>] autoremove_wake_function+0x0/0x30
 [<c0121a9b>] complete+0x2b/0x40
 [<c0135140>] worker_thread+0x0/0xc0
 [<c0137e24>] kthread+0x44/0x70
 [<c0137de0>] 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: [<c044bf65>] remove_exception+0x5/0x20 SS:ESP 0068:ecbcbec0
---[ end trace 25afcedfe7eb0a2b ]---

Is this known problem or something new? Thanks


Mikulas Patocka wrote:
> On Thu, 23 Oct 2008, aluno3@poczta.onet.pl wrote:
>
>   
>> I used dm-snapshot-fix-primary-pe-race.patch and last patch related with
>> pending_exception.After the same test and workload everything work
>> correctly so far.Is it final patch?
>>     
>
> Yes, these two patches are expected to be the final fix. Thanks for the 
> testing. If you get some more crashes even with these two, write about 
> them.
>
> Mikulas
>
>   
>> best and thanks
>>
>>
>> Mikulas Patocka wrote:
>>     
>>> Oh, sorry for this "struct struct" in the patch in free_pending_exception, 
>>> replace it just with one "struct". I forgot to refresh the patch before 
>>> sending it.
>>>
>>> Mikulas
>>>
>>> On Wed, 22 Oct 2008, Mikulas Patocka wrote:
>>>
>>>   
>>>       
>>>> On Wed, 22 Oct 2008, aluno3@poczta.onet.pl wrote:
>>>>
>>>>     
>>>>         
>>>>> Hi
>>>>>
>>>>> I used your patch and I ran test the same workload. After a few hours
>>>>> test, everything is OK. Is it possible? Test is still running.When I get
>>>>> something wrong from kernel I write to You again.
>>>>>       
>>>>>           
>>>> Hi
>>>>
>>>> That's good that it works. So try this. Keep the first patch (it is this 
>>>> one --- 
>>>> http://people.redhat.com/mpatocka/patches/kernel/2.6.27/dm-snapshot-fix-primary-pe-race.patch 
>>>> --- I think Milan already sent it to you and you have it applied). Undo 
>>>> the second patch (that one that hides deallocation with /* */ ). And apply 
>>>> this. Run the same test.
>>>>
>>>> Mikulas
>>>>
>>>> ---
>>>>  drivers/md/dm-snap.c |   10 +++++++++-
>>>>  drivers/md/dm-snap.h |    2 ++
>>>>  2 files changed, 11 insertions(+), 1 deletion(-)
>>>>
>>>> Index: linux-2.6.27-clean/drivers/md/dm-snap.c
>>>> ===================================================================
>>>> --- linux-2.6.27-clean.orig/drivers/md/dm-snap.c	2008-10-22 15:41:24.000000000 +0200
>>>> +++ linux-2.6.27-clean/drivers/md/dm-snap.c	2008-10-22 15:51:33.000000000 +0200
>>>> @@ -368,6 +368,7 @@ static struct dm_snap_pending_exception 
>>>>  	struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
>>>>  							     GFP_NOIO);
>>>>  
>>>> +	atomic_inc(&s->n_pending_exceptions);
>>>>  	pe->snap = s;
>>>>  
>>>>  	return pe;
>>>> @@ -375,7 +376,10 @@ static struct dm_snap_pending_exception 
>>>>  
>>>>  static void free_pending_exception(struct dm_snap_pending_exception *pe)
>>>>  {
>>>> -	mempool_free(pe, pe->snap->pending_pool);
>>>> +	struct struct dm_snapshot *s = pe->snap;
>>>> +	mempool_free(pe, s->pending_pool);
>>>> +	smp_mb__before_atomic_dec();
>>>> +	atomic_dec(&s->n_pending_exceptions);
>>>>  }
>>>>  
>>>>  static void insert_completed_exception(struct dm_snapshot *s,
>>>> @@ -601,6 +605,7 @@ static int snapshot_ctr(struct dm_target
>>>>  	s->valid = 1;
>>>>  	s->active = 0;
>>>>  	s->last_percent = 0;
>>>> +	atomic_set(&s->n_pending_exceptions, 0);
>>>>  	init_rwsem(&s->lock);
>>>>  	spin_lock_init(&s->pe_lock);
>>>>  	s->ti = ti;
>>>> @@ -727,6 +732,9 @@ static void snapshot_dtr(struct dm_targe
>>>>  	/* After this returns there can be no new kcopyd jobs. */
>>>>  	unregister_snapshot(s);
>>>>  
>>>> +	while (atomic_read(&s->n_pending_exceptions))
>>>> +		yield();
>>>> +
>>>>  #ifdef CONFIG_DM_DEBUG
>>>>  	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
>>>>  		BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
>>>> Index: linux-2.6.27-clean/drivers/md/dm-snap.h
>>>> ===================================================================
>>>> --- linux-2.6.27-clean.orig/drivers/md/dm-snap.h	2008-10-22 15:45:08.000000000 +0200
>>>> +++ linux-2.6.27-clean/drivers/md/dm-snap.h	2008-10-22 15:46:49.000000000 +0200
>>>> @@ -163,6 +163,8 @@ struct dm_snapshot {
>>>>  
>>>>  	mempool_t *pending_pool;
>>>>  
>>>> +	atomic_t n_pending_exceptions;
>>>> +
>>>>  	struct exception_table pending;
>>>>  	struct exception_table complete;
>>>>  
>>>>
>>>> --
>>>> dm-devel mailing list
>>>> dm-devel@redhat.com
>>>> https://www.redhat.com/mailman/listinfo/dm-devel
>>>>
>>>>     
>>>>         
>>>   
>>>       
>
>
>