[lvm-devel] lvmcache in writeback mode gets stuck flushing dirty blocks

[Nikhil Kshirsagar]

Please see

https://bugzilla.redhat.com/show_bug.cgi?id=1665650
and
https://bugzilla.redhat.com/show_bug.cgi?id=1661987

Fixed by the migration threshold fix in
https://bugzilla.redhat.com/show_bug.cgi?id=1665654 I think.

Regards,
nikhil.

On Tue, Jul 30, 2019 at 1:32 PM Nikhil Kshirsagar <nkshirsa at redhat.com>
wrote:

> This used to happen if the chunksize increased as a result of needing to
> use more than a million chunks to store the size of the cached lv. What is
> the size of the pool?
>
> Regards,
> Nikhil.
>
> On Tue, 30 Jul, 2019, 1:25 PM Lakshmi Narasimhan Sundararajan, <
> lns at portworx.com> wrote:
>
>> Hi Team,
>>
>> A very good day to all.
>>
>>
>> I am using lvmcache in writeback mode. When there are dirty blocks still
>> in the lv, and if needs to be destroyed or flushed, then
>>
>> It seems to me that there are some conditions under which the dirty data
>> flush gets stuck forever.
>>
>>
>>
>>
>>
>> As an example:
>>
>> root at pdc4-sm35:~# lvremove -f pwx0/pool
>>
>>   367 blocks must still be flushed.
>>
>>   367 blocks must still be flushed.
>>
>>   367 blocks must still be flushed.
>>
>>   367 blocks must still be flushed.
>>
>>   367 blocks must still be flushed.
>>
>>   367 blocks must still be flushed.
>>
>> ^C
>>
>> root at pdc4-sm35:~#
>>
>>
>>
>> I am running these version:
>>
>> root at pdc4-sm35:~# lvm version
>>
>>   LVM version:     2.02.133(2) (2015-10-30)
>>
>>   Library version: 1.02.110 (2015-10-30)
>>
>>   Driver version:  4.34.0
>>
>> root at pdc4-sm35:~#
>>
>>
>>
>>
>>
>> This issue seems old and reported multiple places. There have been some
>> acknowledgement that this issue is resolved in 2.02.133, but still I see
>> it. Also, I have seen some posts report it in 2.02.170+ as well (here:
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878441) (Package: lvm2
>> Version: 2.02.173-1 Severity: normal)
>>
>>
>>
>> I filed one here myself, https://github.com/lvmteam/lvm2/issues/22,
>> trying  to understand from you experts where we are on this?
>>
>>
>>
>> I would sincerely appreciate your help in understanding the state of this
>> issue in more detail.
>>
>>
>>
>> Best regards
>> LN
>>
>> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
>> Windows 10
>>
>>
>> --
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>> lvm-devel at redhat.com
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>
>
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