How to avoid long downtime at reboot due to relabelling when going from SELinux disabled to permissive mode ?

Issue

• System goes in the SELinux autorelabel process (automatically) when you switch SELinux state from Disabled to Permissive mode and reboot the server.
  This autorelabel process takes a long time based on how large the filesystem is and how many file it need to relabel on boot and can take quite long for large filesystem which causes a long downtime.
  How to avoid long booting time when switching SELinux from Disabled mode to Permissive mode ?

• Is there a way to exclude large file system form the SELinux autorelabel process to avoid long time during reboot ?

• Can we relabel large filesystem manually post bootup to Permissive mode and avoid them from being relabeled during boot ?