using the overlay option causes kernel warnings "upper fs does not support file handles"

Using the --overlay option causes kernel warnings:
```
[649407.156601] overlayfs: upper fs does not support file handles, falling back to index=off.
[649407.156607] overlayfs: fs on '/proc/self/fd/9' does not support file handles, falling back to xino=off.
```
The overlay functionality works fine, but since I run this command frequently, it is spamming the kernel logs with these warnings.
I would like to get rid of them. Not sure what would be the cleanest approach, perhaps adding an option: `--overlay-opt OPT`
Which would allow me to explicitly turn off the default mount flags that cause these warnings, for example with:
`--overlay-opt index=off,xino=off`
Perhaps alternatively those mount options could just be used by default, but I'm not sure that's the best solution.
Would you consider implementing such an option or maybe accept a patch that does that, if that is the correct approach?