Use EXDEV to reject cross MDS link:
Use EXDEV to reject cross MDS link:

zhihui@lime: /zzh111$ ln PSC1/ls.txt PSC2/testdir/linkit
ln: failed to create hard link ‘PSC2/testdir/linkit’ => ‘PSC1/ls.txt’: Invalid cross-device link



git-svn-id: ae92b08b608af1c8cefa3e10d2325ea527204e07@25265 3eda493b-6a19-0410-b2e0-ec8ea4dd8fda

pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable