Merge commit 79a357c2a from openzfs git (by Adrian Chadd):
Fix pointer-is-uint64_t-sized assumption in the ioctl path This shows up when compiling freebsd-head on amd64 using gcc-6.4. The lib32 compat build ends up tripping over this assumption. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: adrian chadd <adrian@freebsd.org> Closes #11068 Closes #11069