Re: Is there a way to flag specific directories "nodatacow"?

[George Mitchell <george@chinilu.com>]

On 06/02/2013 06:28 PM, Liu Bo wrote:
> On Sun, Jun 02, 2013 at 07:40:52AM -0700, George Mitchell wrote:
>> I am seeing massive journal corruptions that seem to be unique to
>> btrfs and I am suspecting that cow might be causing them.  My
>> bandaid fix for this will be to mark the /var filesystem "nodatacow"
>> at boot.  But I am wondering if their is any way to flag a
>> particular directory as "nodatacow" outside of the mount process.  I
>> would like to be able to mark /var/log/journal as "nodatacow" for
>> example, without having to declare it a subvolume and mount it
>> separately.
> Hi George,
>
> We actually have per-file/directory nodatacow :)
>
> But please note if you set nodatacow on the particular directory, only
> new-created or zero-size files in the directory can follow the nocow rule.
>
> 'chattr' in the latest e2fsprogs can fit your requirements,
> # chattr +C /var/log/journal
>
> Also, what kind of massive journal corruptions?  Does it look like a
> btrfs specific bug?
>
> thanks,
> liubo
>
>
I am also assuming that all directories later created under 
/var/log/journal will inherit the nodatacow profile?