<header>Disable subtree checking?</header>

This option disables subtree  checking,  which  has  mild
security  implications,  but  can  improve reliability in
some circumstances. <p>

If a subdirectory of a filesystem is  exported,  but  the
whole  filesystem  isn't then  whenever  a  NFS  request
arrives, the server must check not only that the accessed
file is in the appropriate filesystem (which is easy) but
also that it is in the exported tree (which  is  harder). <p>

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