sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
     When a da or ada device dissappears, outstanding IOs fail with
     ENXIO, not EIO.  The check for EIO was probably copied from Illumos,
     where that is indeed the correct errno.

     Without this change, pulling a busy drive from a zpool would usually
     turn it into UNAVAIL, even though pulling an idle drive would turn
     it into REMOVED.  With this change, it is REMOVED every time.

     Also, vdev_geom_io_intr shouldn't do zfs_post_remove, because that
     results in devd getting two resource.fs.zfs.removed events.  The
     comment said that the event had to be sent directly instead of
     through the async removal thread because "the DE engine is using
     this information to discard prevoius I/O errors".  However, the fact
     that vdev_geom_io_intr was never actually sending the events until
     now, and that vdev_geom_orphan never sent them at all, and that
     vdev_geom_orphan usually gets called about 2 seconds after the
     actual removal, means that FreeBSD's userland can cope with a late
     event just fine.