From mboxrd@z Thu Jan  1 00:00:00 1970
From: Miklos Szeredi <miklos@szeredi.hu>
Subject: Re: Optional switching off cow in overlayfs
Date: Mon, 22 Jun 2015 16:37:47 +0200
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To: Jan Olszak <j.olszak@samsung.com>
Cc: David Howells <dhowells@redhat.com>, "linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>

On Mon, Jun 22, 2015 at 4:26 PM, Jan Olszak <j.olszak@samsung.com> wrote:
>> You can bind mount individual files from the lower layer to the
>> overlay.  That fixes the "allow modification" part.
>
> Well bind mounting every file that should have COW is unmaintainable - if
> new files appear admin has to mount each one.

No.  I was proposing bind mounts for non-COW ones.

mount -t overlay -olowerdir=/lower,upperdir=/upper,workdir=/work  overlay /ovl
mount --bind /lower/this-file-is-non-cow /ovl/this-file-is-non-cow
...

>>   But what should happen on rename or unlink?
>
> Both would operate on the original inode.

And that would make this hugely complex.

Thanks,
Miklos