illumos-gate commit bbfa8ea8bb4168c969ba27d632dfe0aeec3fc0da
Author: Matthew Ahrens <mahrens@delphix.com>
Date:   Thu Jul 17 09:27:13 2014 -0800

    4631 zvol_get_stats triggering too many reads
    Reviewed by: Adam Leventhal <ahl@delphix.com>
    Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
    Reviewed by: Matt Ahrens <mahrens@delphix.com>
    Approved by: Dan McDonald <danmcd@omniti.com>

Original commit ported by Boris Protopopov