MFV r267569:

4897 Space accounting mismatch in L2ARC/zpool

illumos/illumos-dist@3038a2b421b40dc5ac11cd88423696618584f85a

MFC after:	2 weeks
MFV r267570:

4756 metaslab_group_preload() could deadlock

illumos/illumos-gate@30beaff42d8240ebf5386e8b7a14e3d137a1631f

MFC after:	2 weeks