Date: Tue, 15 Apr 2014 18:27:34 +0200
From: David Sterba <dsterba@suse.cz>
To: Chris Mason <clm@fb.com>
Cc: linux-btrfs@vger.kernel.org, Miao Xie <miaox@cn.fujitsu.com>,
        Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Subject: Re: [PATCH 1/2] btrfs: protect snapshots from deleting during send
Message-ID: <20140415162734.GX29256@suse.cz>
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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?