mount overlay failure I am having read-write JFFS2 FS mounted on a MTD partition. Later in the boot sequence I am overlaying a read-only FS into this read-write FS. mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,workdir=/work /merged I see mount overlay failure when my read-write FS is almost (like 99%) full. The mount overlay failure error output suggest me its not able to create new directories in the 'workdir' because its full. The 'workdir' is part of the same read-write partition. How would someone estimate how much space would be required in the 'workdir' so that the mount overlay does not fail. Overlay documentation suggest that the 'workdir' is used for staging purpose. How to make it fail-safe? I am using this overlay-fs as my rootfs so mount failure here result in kernel panic.

make sure /work directory exists always. Before overlay this directory can be cleaned up if required. The first thing overlay does is to create the /work directory if it does not exists. The failure comes from this directory creation if the rw-fs is full as the fs does not allow new directory creation. If one can ensure that /work directory exists always then the mount overlay would still work even if the read-write fs is full.