Re: empty directory from previous subvolume in a snapshot is not sent|received

[Andrei Borzenkov <arvidjaar@gmail.com>]

On 22.06.2023 19:09, Christoph Anton Mitterer wrote:
> On Thu, 2023-06-22 at 18:22 +0300, Andrei Borzenkov wrote:
>> I think it is expected. btrfs does not support either recursive
>> snapshots or recursive send so "btrfs send" skips directory entry
>> that
>> points to subvolume root.
> 
> Well it's clear that the sub-volume is not contained in the snapshot or
> sent.
> 
> But in the snapshot (on the original fs) I have the empty directory
> from the subvolume that was not recursively snapshotted.

It is not directory. It is "orphan subvolume graft point" for the lack 
of better term.

tw:/mnt # btrfs subvolume create ./data/pictures
Create subvolume './data/pictures'
tw:/mnt # btrfs subvolume snapshot data/ snap1
Create a snapshot of 'data/' in './snap1'
tw:/mnt # ll snap1
total 0
drwxr-xr-x 1 root root 0 Jun 23 07:53 pictures
tw:/mnt # touch snap1/pictures/foo
touch: cannot touch 'snap1/pictures/foo': Permission denied
tw:/mnt #


> Shouldn't that be just a plain empty directory... and thus be
> sent|received (as empty directory) when I send|receive the snapshot?
> 
> 
> Cheers,
> Chris.