Re: [PATCH] ovl: Allow changing default fsync_mode

On Tue, Jun 23, 2026 at 5:00 PM Gao Xiang <[email protected]> wrote:
>
>
>
> On 2026/6/23 16:43, Yafang Shao wrote:
> > We have enabled "volatile" fsync_mode on our Kubernetes production
> > environment to prevent container exit from being blocked when there
> > are many dirty pages to flush. This has worked well without introducing
> > any issues.
> >
> > However, on some of our production servers, upgrading the container
> > runtime to support the "volatile" mount option is not straightforward [0].
> > To address this, we want to enable it by default within the kernel.
>
> Just a side note: "upgrade the container runtime is not
> straightforward", how? it seems that issue is already resolved and
> there is no more discussion.

We still have many production servers running Docker, while the
"volatile" mount option is only supported by containerd. Upgrading
from Docker to containerd is a difficult process.

>
> Not quite sure applying a default volatile policy is quite feasible,
> especially the issue documented in
> https://github.com/containerd/containerd/pull/10274/files#diff-9239161e2af83fd84df5792f9fe64701c517fe4598eae60d4d245d039955f46cR33
>
> then userspace cannot drop `volatile` option as a somewhat
> workaround now.

OS vendors can still set "auto" as the default config, while customers
can override it dynamically via sysfs. We have been running with
"volatile" on many production servers across different workloads for
over a year, and it has worked as expected without any issues.

-- 
Regards
Yafang