Re: [PATCH 1/2] btrfs: protect snapshots from deleting during send

[Chris Mason <clm@fb.com>]

On 04/15/2014 12:27 PM, David Sterba wrote:
> On Tue, Apr 15, 2014 at 12:00:49PM -0400, Chris Mason wrote:
>>>> I'm worried about the use case where we have:
>>>>
>>>>    * periodic automated snapshots
>>>>    * periodic automated deletion of old snapshots
>>>>    * periodic send for backup
>>>>
>>>> The automated deletion doesn't want to error out if send is in progress, it
>>>> just wants the deletion to happen in the background.
>>>
>>> I'd give the precedence to the 'backup' process before the 'clean old
>>> snapshots', because it can do more harm if the snapshot is removed
>>> meanwhile without any possibility to recover.
>>
>> Right, we don't want either process to stop with an error.  We just want
>> them to continue happily and do the right thing...
>
> ... if everything goes without errors. Not like send going out of
> memory, send through network has a glitch, send to a file runs out of
> space, and has to be restarted. Is this too unrealistic to happen?
>

It's a good point, a better way to say what I have in mind is that we 
shouldn't be adding new transient errors to the send process (on purpose ;)

-chris