Pull overlayfs fixes from Miklos Szeredi:
"This fixes minor issues with the multi-layer update in v4.0"
* 'overlayfs-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: upper fs should not be R/O
ovl: check lowerdir amount for non-upper mount
ovl: print error message for invalid mount options