eCryptfs: Invalidate dcache entries when lower i_nlink is zero
eCryptfs: Invalidate dcache entries when lower i_nlink is zero

Consider eCryptfs dcache entries to be stale when the corresponding
lower inode's i_nlink count is zero. This solves a problem caused by the
lower inode being directly modified, without going through the eCryptfs
mount, leaving stale eCryptfs dentries cached and the eCryptfs inode's
i_nlink count not being cleared.

Signed-off-by: Tyler Hicks <93eeee00a2beb1fbd6106ad8f59025f171ca91c6@canonical.com>
Reported-by: Richard Weinberger <320bca71fc381a4a025636043ca86e734e31cf8b@nod.at>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs