commit c7944ebb9ce9461079659e9e6ec5baaf73724b3b upstream.

If we're revalidating an existing dentry in order to open a file, we need
to ensure that we check the directory has not changed before we optimise
away the lookup.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NQian Lu <luqia@amazon.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>