[Users] ploop on ext4 without journal - bug?

[Nick Knutov]

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Thanks,

yes, I'm using SSDs.

Partition was
tune2fs -O ^has_journal /dev/sdX
so I thought the journal was removed completely and data= section is not
important at all.

Ok, what is the right way to fix it for me now?
Will
remount with data=ordered (and still tune2fs -O ^has_journal)
be fine?

Was that fixed bug already compiled and sent to yum repository (package
ploop I suppose) ?


07.10.2015 17:03, Dmitry Monakhov пишет:
> Sergey Bronnikov <sergeyb at openvz.org> writes:
>
>> Dima, could you help?
>>
>> On 02:08 Wed 30 Sep , Nick Knutov wrote:
>>> Hello all,
>>>
>>> I have an ext4 partition without journal (I need it so):
> First of all. The subject you mentioned is incorrect. This is not
> nojournal mode. Configuration you want to create is external journal
with data=journal.
>
> data=journal is full data journaling mode. Such mode assumes that it
> will pass through journal all data, but ploop directly issues bios to
> lower-fs(i.e. baypass journal). This done for performance reasons. That
> is why ploop is faster that any other solutions.
> All this means that full journaling for lower(/vz/private) fs is not
> compatible with ploop. So please do not use it, otherwise you'll get
> undefined behavior (most likely silent corruptions in guest-fs)
>
> The glitch you have mentioned most likely happen due to the fact that
> you use SSD. Recently we have found a bug in mm reclaim code which
> result in deadlock (swap on ssd in our case)
https://jira.sw.ru/browse/PSBM-39335
>
> Bug was fixed here:
> *diff-ms-mm-vmscan-do-not-wait-for-page-writeback-for-GFP_NOFS-allocations
> Added to 042stab112_3
>
> mm, vmscan: Do not wait for page writeback for GFP_NOFS
> Backport of mainline patch ecf5fc6e9654
>
>>>
>>> mount | grep vz2
>>> /dev/sde1 on /vz2 type ext4
(rw,relatime,discard,errors=remount-ro,commit=20,data=journal,journal_async_commit)
>>>
>>> debugfs -R features /dev/sde1
>>> debugfs 1.41.12 (17-May-2010)
>>> Filesystem features: ext_attr resize_inode dir_index filetype extent
flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
>>>
>>> When I'm trying to create CT with ploop layout - I've got
>>>
>>> Creating image: /vz2/private/2008.tmp/root.hdd/root.hdd size=10485760K
>>> Creating delta /vz2/private/2008.tmp/root.hdd/root.hdd bs=2048
size=20971520 sectors v2
>>> Storing /vz2/private/2008.tmp/root.hdd/DiskDescriptor.xml
>>> WARNING: /vz2 is mounted with data=writeback not recommended for
ploop; please use data=ordered instead
>>> Opening delta /vz2/private/2008.tmp/root.hdd/root.hdd
>>> Adding delta dev=/dev/ploop58376
img=/vz2/private/2008.tmp/root.hdd/root.hdd (rw)
>>>
>>> and now it freezes. (btw, vzctl says it's data=writeback, but it's
>>> data=journal and journal is removed - is it ok?)
>>>
>>>
>>> When ctrl+c I've got:
>>>
>>> ^C
>>> Cancelling...
>>> Cancelling...
>>> Destroying container private area: /vz2/private/2008.tmp
>>> ^C
>>> Cancelling...
>>> Cancelling...
>>>
>>> so I have to log in other ssh session and kill -9 it.
>>>
>>> Kernel: 042stab108.8
>>>
>>> Is it a bug or I'm doing something wrong?
>>>
>>> --
>>> Best Regards,
>>> Nick Knutov
>>> http://knutov.com
>>> ICQ: 272873706
>>> Voice: +7-904-84-23-130
>>>
>>
>>> _______________________________________________
>>> Users mailing list
>>> Users at openvz.org
>>> https://lists.openvz.org/mailman/listinfo/users

- -- 
Best Regards,
Nick Knutov
http://knutov.com
ICQ: 272873706
Voice: +7-904-84-23-130
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