irtual address differ.  Also, we can further simplify the
code by removing the special case for a single buffer by noticing that
it doesn't matter if we use a page size that is too big.  This allows
the loop to compute the page shift to be replaced with __ffs().

Thanks to Bryan S Rosenburg <rosnbrg@us.ibm.com> for pointing out the
original bug and suggesting several ways to improve this patch.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Œ†-ª— x