btrfs send 3.11 vs 3.12

btrfs send 3.11 vs 3.12

[Miguel Negrão]

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Hi

Sending snapshots incrementally started to fail on the 3.11 kernel on my
system after I once booted with 3.12 and did the incremental send of a
snapshot. After when I booted back to 3.11 I can no longer send the
snapshots incrementally based on the last one sent (I could still send
based on the last one sent from 3.11), although booting again to 3.12 I
can send me fine again.

It this intenteded ?

best,
-- 
Miguel Negrão
http://www.friendlyvirus.org/miguelnegrao


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Re: btrfs send 3.11 vs 3.12

[Joshua Schüler]

Am 23.01.2014 10:22, schrieb Miguel Negrão:
> Hi
> 
> Sending snapshots incrementally started to fail on the 3.11 kernel
>  on my system after I once booted with 3.12 and did the incremental
>  send of a snapshot. After when I booted back to 3.11 I can no 
> longer send the snapshots incrementally based on the last one sent
>  (I could still send based on the last one sent from 3.11), 
> although booting again to 3.12 I can send me fine again.
> 
> It this intenteded ?
> 
> best,
> 

Hi Miguel,

btrfs guarantees backward compatibility since 3.13(?), but never
guaranteed forward compatibility. So it is not yet supported to mount
the fs with an older kernel once it was mounted with a newer one.
Especially when using features that are under heavy development right now.

Also try to keep your kernel up to date (3.13 is out since a few days)

Joshua

Re: btrfs send 3.11 vs 3.12

[David Sterba]

On Thu, Jan 23, 2014 at 01:28:54PM +0100, Joshua Schüler wrote:
> btrfs guarantees backward compatibility since 3.13(?), but never
> guaranteed forward compatibility.

Isnt' this the opposite way? Forward means that old fs will be mountable
on a newer kernel.

I don't know what you mean by 'backward compatibility is guaranteed
since 3.13'. There are some features that get turned on automatically if
used for the first time, but not all of them prevent mounting on an
older kernel. Exmaple is the uuid tree, "generation v2" that's been
introduced with send. Older kernel ignores the changes and newer kernel
is usually able to recognize that the data are not all-ok and recovers
itself or allows the user to do so manually.

> So it is not yet supported to mount the fs with an older kernel once
> it was mounted with a newer one.

That's right, but in practice is not that bad.

> Especially when using features that are under heavy development right now.

Which features do you mean? Once a feature is introduced, the format
and incompatibility bits should not change. The code may change, and
does of course, but always in a compatible way.

Re: btrfs send 3.11 vs 3.12

[Josef Bacik]

On 01/23/2014 04:22 AM, Miguel Negrão wrote:
> Hi
>
> Sending snapshots incrementally started to fail on the 3.11 kernel on my
> system after I once booted with 3.12 and did the incremental send of a
> snapshot. After when I booted back to 3.11 I can no longer send the
> snapshots incrementally based on the last one sent (I could still send
> based on the last one sent from 3.11), although booting again to 3.12 I
> can send me fine again.
>
> It this intenteded ?
This is definitely not intended, I will look into why this is 
happening.  Thanks,

Josef

Re: btrfs send 3.11 vs 3.12

[Miguel Negrão]

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Em 23-01-2014 14:19, Josef Bacik escreveu:
> 
> On 01/23/2014 04:22 AM, Miguel Negrão wrote:
>> Hi
>>
>> Sending snapshots incrementally started to fail on the 3.11 kernel on my
>> system after I once booted with 3.12 and did the incremental send of a
>> snapshot. After when I booted back to 3.11 I can no longer send the
>> snapshots incrementally based on the last one sent (I could still send
>> based on the last one sent from 3.11), although booting again to 3.12 I
>> can send me fine again.
>>
>> It this intenteded ?
> This is definitely not intended, I will look into why this is
> happening.  Thanks,

Great, thanks.  The error:

> miguel@miguel-MacBookPro:~$ sudo btrfs send -p /mnt/ssd/backups/@-2014-01-22-11\:29/ /mnt/ssd/backups/@-2014-01-23-17\:51/ | sudo btrfs receive /media/miguel/backup/backups/@ 
> At subvol /mnt/ssd/backups/@-2014-01-23-17:51/
> At snapshot @-2014-01-23-17:51
> ERROR: could not find parent subvolume

> miguel@miguel-MacBookPro:~$ ls -l /media/miguel/backup/backups/@
> total 0
...
> drwxr-xr-x 1 root root 358 Jan 22 11:31 @-2014-01-22-11:29

Don't know if it's relevant, but I'm already mounting the filesystem
with subvolid=5 since was an issue too:

> sudo mount -o subvolid=5 -U f2e4e4d3-2d8e-4764-a818-de9176405c4b /mnt/ssd

best,
Miguel






-- 
Miguel Negrão
http://www.friendlyvirus.org/miguelnegrao


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Re: btrfs send 3.11 vs 3.12

[Felix Blanke]

Hi,

please take a look into this thread:

http://www.spinics.net/lists/linux-btrfs/msg30573.html

I had a similiar problem and got the answer + a fix from the list.

Regards,
Felix

On Thu, Jan 23, 2014 at 6:58 PM, Miguel Negrão
<miguel.negrao-lists@friendlyvirus.org> wrote:
> Em 23-01-2014 14:19, Josef Bacik escreveu:
>>
>> On 01/23/2014 04:22 AM, Miguel Negrão wrote:
>>> Hi
>>>
>>> Sending snapshots incrementally started to fail on the 3.11 kernel on my
>>> system after I once booted with 3.12 and did the incremental send of a
>>> snapshot. After when I booted back to 3.11 I can no longer send the
>>> snapshots incrementally based on the last one sent (I could still send
>>> based on the last one sent from 3.11), although booting again to 3.12 I
>>> can send me fine again.
>>>
>>> It this intenteded ?
>> This is definitely not intended, I will look into why this is
>> happening.  Thanks,
>
> Great, thanks.  The error:
>
>> miguel@miguel-MacBookPro:~$ sudo btrfs send -p /mnt/ssd/backups/@-2014-01-22-11\:29/ /mnt/ssd/backups/@-2014-01-23-17\:51/ | sudo btrfs receive /media/miguel/backup/backups/@
>> At subvol /mnt/ssd/backups/@-2014-01-23-17:51/
>> At snapshot @-2014-01-23-17:51
>> ERROR: could not find parent subvolume
>
>> miguel@miguel-MacBookPro:~$ ls -l /media/miguel/backup/backups/@
>> total 0
> ...
>> drwxr-xr-x 1 root root 358 Jan 22 11:31 @-2014-01-22-11:29
>
> Don't know if it's relevant, but I'm already mounting the filesystem
> with subvolid=5 since was an issue too:
>
>> sudo mount -o subvolid=5 -U f2e4e4d3-2d8e-4764-a818-de9176405c4b /mnt/ssd
>
> best,
> Miguel
>
>
>
>
>
>
> --
> Miguel Negrão
> http://www.friendlyvirus.org/miguelnegrao
>