Major Description
The javadocs for DiskChecker#checkDir(File dir) trail off, look like they weren't completed, should be.
While checkDir(File) uses java File to check if a dir actually is writable, the version of checkDir that takes an FsPermission uses FsAction#implies which doesn't actually check if a dir is writable (eg it passes on a read-only file system). So switching from one version to the other can cause unexpected bugs. Let's call this out explicitly in the javadocs.