Re: [ptxdist] [PATCH] varoverlayfs: support kernels without metacopy

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Thu, Feb 13, 2020 at 06:22:07PM +0100, Matthias Schiffer wrote:
> metacopy=on is supported on Linux 4.19+. Add fallback for older kernels.

I think we should just drop the option. It's just a nice-to-have feature
and in most cases, it does not make a any difference. The lower filesystem
is usually empty, except for directories and maybe very small files.

Michael

> 
> Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
> ---
>  projectroot/usr/lib/systemd/system/var.mount | 1 -
>  projectroot/usr/sbin/mount.varoverlayfs      | 4 +++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/projectroot/usr/lib/systemd/system/var.mount b/projectroot/usr/lib/systemd/system/var.mount
> index bd6350237..3b686a260 100644
> --- a/projectroot/usr/lib/systemd/system/var.mount
> +++ b/projectroot/usr/lib/systemd/system/var.mount
> @@ -8,4 +8,3 @@ Where=/var
>  # note: this is a dummy filesystem only to trigger the corresponding mount helper
>  What=varoverlayfs
>  Type=varoverlayfs
> -Options=metacopy=on
> diff --git a/projectroot/usr/sbin/mount.varoverlayfs b/projectroot/usr/sbin/mount.varoverlayfs
> index 913004d15..efab16aef 100644
> --- a/projectroot/usr/sbin/mount.varoverlayfs
> +++ b/projectroot/usr/sbin/mount.varoverlayfs
> @@ -8,6 +8,8 @@ set -e
>  systemctl start run-varoverlayfs.mount
>  mkdir -p /run/varoverlayfs/upper
>  mkdir -p /run/varoverlayfs/work
> -mount -t overlay -olowerdir=/var,upperdir=/run/varoverlayfs/upper,workdir=/run/varoverlayfs/work "${@}"
> +# metacopy=on is supported on Linux 4.19+, fall back on older kernels
> +mount -t overlay -olowerdir=/var,upperdir=/run/varoverlayfs/upper,workdir=/run/varoverlayfs/work,metacopy=on "${@}" ||
> +	mount -t overlay -olowerdir=/var,upperdir=/run/varoverlayfs/upper,workdir=/run/varoverlayfs/work "${@}"
>  systemctl stop run-varoverlayfs.mount
>  rmdir /run/varoverlayfs
> -- 
> 2.17.1
> 
> 
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> 

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