zfs deadlock
krichy at cflinux.hu
krichy at cflinux.hu
Sat Dec 7 13:38:27 UTC 2013
Dear Steven,
A crash is very easily reproducible with the attached script, just make
an empty dataset, make a snapshot of it,
and run the script.
In my virtual machine it crashed in a few seconds, producing the
attached output.
Regards,
2013-12-06 17:28 időpontban krichy at cflinux.hu ezt írta:
> Dear Steven,
>
> using the previously provided scripts, the bug still appears. And I
> got the attaches traces when the deadlock occured.
>
> It seems that one process is in zfs_mount(), while the other is in
> zfs_unmount_snap(). Look for the 'zfs' and 'ls' commands.
>
> Hope it helps.
>
> Regards,
> 2013-12-06 16:59 időpontban krichy at cflinux.hu ezt írta:
>> So maybe the force flag is too strict. Under linux the snapshots
>> remains mounted after a send.
>>
>> 2013-12-06 16:54 időpontban krichy at cflinux.hu ezt írta:
>>> Dear Steven,
>>>
>>> Of course. But I got further now. You mentioned that is normal that
>>> zfs send umounts snapshots. I dont know, but this indeed causes a
>>> problem:
>>>
>>> It is also reproducible without zfs send.
>>> 1. Have a large directory structure (just to make sure find runs long
>>> enough), make a snapshot of it.
>>> # cd /mnt/pool/set/.zfs/snapshot/snap
>>> # find .
>>>
>>> meanwhile, on another console
>>> # umount -f /mnt/pool/set/.zfs/snapshot/snap
>>>
>>> will cause a panic, or such.
>>>
>>> So effectively a regular user on a system can cause a crash.
>>>
>>> Regards,
>>>
>>> 2013-12-06 16:50 időpontban Steven Hartland ezt írta:
>>>> kernel compiled, installed and rebooted?
>>>> ----- Original Message ----- From: <krichy at cflinux.hu>
>>>> To: <smh at FreeBSD.org>
>>>> Sent: Friday, December 06, 2013 12:17 PM
>>>> Subject: Fwd: Re: zfs deadlock
>>>>
>>>>
>>>>> Dear shm,
>>>>>
>>>>> I've applied r258294 on top fo releng/9.2, but my test seems to
>>>>> trigger
>>>>> the deadlock again.
>>>>>
>>>>> Regards,
>>>>>
>>>>> -------- Eredeti üzenet --------
>>>>> Tárgy: Re: zfs deadlock
>>>>> Dátum: 2013-12-06 13:17
>>>>> Feladó: krichy at cflinux.hu
>>>>> Címzett: freebsd-fs at freebsd.org
>>>>>
>>>>> I've applied r258294 on top of releng/9.2, and using the attached
>>>>> scripts parallel, the system got into a deadlock again.
>>>>>
>>>>> 2013-12-06 11:35 időpontban Steven Hartland ezt írta:
>>>>>> Thats correct it unmounts the mounted snapshot.
>>>>>>
>>>>>> Regards
>>>>>> Steve
>>>>>>
>>>>>> ----- Original Message ----- From: <krichy at cflinux.hu>
>>>>>> To: "Steven Hartland" <killing at multiplay.co.uk>
>>>>>> Cc: <freebsd-fs at freebsd.org>
>>>>>> Sent: Friday, December 06, 2013 8:50 AM
>>>>>> Subject: Re: zfs deadlock
>>>>>>
>>>>>>
>>>>>>> What is strange also, when a zfs send finishes, the paralell
>>>>>>> running
>>>>>>> find command issues errors:
>>>>>>>
>>>>>>> find: ./e/Chuje: No such file or directory
>>>>>>> find: ./e/singe: No such file or directory
>>>>>>> find: ./e/joree: No such file or directory
>>>>>>> find: ./e/fore: No such file or directory
>>>>>>> find: fts_read: No such file or directory
>>>>>>> Fri Dec 6 09:46:04 CET 2013 2
>>>>>>>
>>>>>>> Seems if the filesystem got unmounted meanwhile. But the script
>>>>>>> is
>>>>>>> changed its working directory to the snapshot dir.
>>>>>>>
>>>>>>> Regards,
>>>>>>>
>>>>>>> 2013-12-06 09:03 időpontban krichy at cflinux.hu ezt írta:
>>>>>>>> Dear Steven,
>>>>>>>>
>>>>>>>> While I was playig with zfs, trying to reproduce the previous
>>>>>>>> bug,
>>>>>>>> accidentaly hit another one, which caused a trace I attached.
>>>>>>>>
>>>>>>>> The snapshot contains directories in 2 depth, which contain
>>>>>>>> files. It
>>>>>>>> was to simulate a vmail setup, with domain/user hierarchy.
>>>>>>>>
>>>>>>>> I hope it is useful for someone.
>>>>>>>>
>>>>>>>> I used the attached two scripts to reproduce the ZFS bug.
>>>>>>>>
>>>>>>>> It definetly crashes the system, in the last 10 minutes it is
>>>>>>>> the 3rd
>>>>>>>> time.
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>> 2013-12-05 20:26 időpontban krichy at cflinux.hu ezt írta:
>>>>>>>>> Dear Steven,
>>>>>>>>>
>>>>>>>>> Thanks for your reply. Do you know how to reproduce the bug?
>>>>>>>>> Because
>>>>>>>>> simply sending a snapshot which is mounted does not
>>>>>>>>> automatically
>>>>>>>>> trigger the deadlock. Some special cases needed, or what?
>>>>>>>>> How to prove that the patch fixes this?
>>>>>>>>>
>>>>>>>>> Regards,
>>>>>>>>> 2013-12-05 19:39 időpontban Steven Hartland ezt írta:
>>>>>>>>>> Known issue you want:
>>>>>>>>>> http://svnweb.freebsd.org/changeset/base/258595
>>>>>>>>>>
>>>>>>>>>> Regards
>>>>>>>>>> Steve
>>>>>>>>>>
>>>>>>>>>> ----- Original Message ----- From: "Richard Kojedzinszky"
>>>>>>>>>> <krichy at cflinux.hu>
>>>>>>>>>> To: <freebsd-fs at freebsd.org>
>>>>>>>>>> Sent: Thursday, December 05, 2013 2:56 PM
>>>>>>>>>> Subject: zfs deadlock
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Dear fs devs,
>>>>>>>>>>>
>>>>>>>>>>> We have a freenas server, which is basicaly a freebsd. I was
>>>>>>>>>>> trying to look at snapshots using ls .zfs/snapshot/.
>>>>>>>>>>>
>>>>>>>>>>> When I issued it, the system entered a deadlock. An NFSD was
>>>>>>>>>>> running, a zfs send was running when I issued the command.
>>>>>>>>>>>
>>>>>>>>>>> I attached to command outputs while the system was in a
>>>>>>>>>>> deadlock
>>>>>>>>>>> state. I tried to issue
>>>>>>>>>>> # reboot -q
>>>>>>>>>>> But that did not restart the system. After a while (5-10
>>>>>>>>>>> minutes)
>>>>>>>>>>> the system rebooted, I dont know if the deadman caused that.
>>>>>>>>>>>
>>>>>>>>>>> Now the system is up and running.
>>>>>>>>>>>
>>>>>>>>>>> It is basically a freebsd 9.2 kernel.
>>>>>>>>>>>
>>>>>>>>>>> Do someone has a clue?
>>>>>>>>>>>
>>>>>>>>>>> Kojedzinszky Richard
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --------------------------------------------------------------------------------
>>>>>>>>>>
>>>>>>>>>>
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