[linux-lvm] problem with lvcreate and redirection

[Марк Коренберг]

> 20 февр. 2016 г., в 1:31, Zdenek Kabelac <zdenek.kabelac at gmail.com> написал(а):
> 
> Dne 19.2.2016 v 19:40 Lentes, Bernd napsal(a):
>> Hi,
>> 
>> i have a script in which i invoke lvremove and lvcreate. With lvremove i don't have proplems but with lvcreate.
>> I'm redirecting stdout and stderr to a file because the script is executed by cron and i'd like to have a look afterwards if everything went fine.
>> The command is: lvcreate -v -L 25G -n lv_root_snapshot -s vg1/lv_root > lvcreate_with_redirection.log 2>&1. Shell does not accept further commands afterwards, but host still responds to ping. You can have a look on lvcreate_with_redirection.log here: https://hmgubox.helmholtz-muenchen.de:8001/d/b4c7025bac/ .
>> System seems to stop while suspending.
>> 
>> last lines of the log:
>> ======================================================
>> 
>> ...
>>     Creating vg1-lv_root_snapshot-cow
>>     Loading vg1-lv_root_snapshot-cow table (252:3)
>>     Resuming vg1-lv_root_snapshot-cow (252:3)
>>     Loading vg1-lv_root_snapshot table (252:1)
>>     Suspending vg1-lv_root (252:0) with filesystem sync with device flush
>> ======================================================
> 
> 
> Unfortunately you can't do that if you log to the SAME volume you are suspending - i.e. you run your command from your root volume
> which is also suspended.
> 
> We could likely 'buffer' the output while in suspend mode,
> and throw out the output later - but as this is seen as 'debug' help it's assume user takes care and user place for logging which doesn't block.
> 
> So if you want to see logs - use something tmpfs location for it.

Why this happen ? I thought that operations with page cache will not be suspended on fsfreeze(). 

> 
> Regards
> 
> 
> Zdenek
> 
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