overlay: Test mount error cases with overlapping layers
Add tests for overlayfs mounts with:
- Same upperdir/lowerdir
- Overlapping upperdir/lowerdir
- Overlapping lowerdir layers
- Overlapping lowerdir with other mount upperdir/workdir
Add test for moving layer into another after mount.
Overlapping layers on mount or lookup results in ELOOP.
Overlapping lowerdir with other mount upperdir/workdir
result in EBUSY.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>