Compatibility with overlayfs

[Gao Xiang]

Hi David,

On Fri, Nov 29, 2019 at 03:22:15PM -0500, David Michael wrote:
> Hi,
> 
> I tried to test EROFS on Linux 5.4 as the root file system and mounted
> a writable overlay (with upper layer on tmpfs) over /etc, but I get
> ENODATA errors when attempting to modify files.  For example, adding a
> user results in "Failed to take /etc/passwd lock: No data available".
> Files can be modified after unlinking and restoring them so they're
> created on the upper layer.  This is not necessary with other
> read-only file systems (at least squashfs or ext4 with the read-only
> feature).  I tried while forcing compact and extended inodes.
> 
> Is EROFS intended to be usable as a lower layer with overlayfs?

Yes, and overlayfs were used on our smartphones for development use
only as well. I think it's weird, I will try it on the latest kernel
now, and see if I can reproduce this issue soon...

Thanks for your report!

Thanks,
Gao Xiang

> 
> Thanks.
> 
> David