zfsonlinux/zfs — pull request #2787 by behlendorf (2014-10-11 01:21:36+00:00)
Title: Handle NULL mirror child vdev

When selecting a mirror child it's possible that map allocated by
vdev_mirror_map_allc() contains a NULL for the child vdev. In
this case the child should be skipped and the read issues to
another member of the mirror.

Signed-off-by: Brian Behlendorf
Issue #1744