MFV r273060:

Use write_psize instead of write_asize when doing vdev_space_update.
Without this change the accounting of L2ARC usage would be wrong and
give 16EB free space because the number became negative and overflows.

Obtained from:  FreeNAS (issue #6239)
MFC r272506: MFV r272495:

In arc_kmem_reap_now(), reap range_seg_cache too to reclaim memory in
response of memory pressure.

Illumos issue:
    5163 arc should reap range_seg_cache
MFC r272527:

Don't make nested definition for range_seg_cache.

Reported by:	ian
MFC r272583: MFV r272500:

Don't inherit flags other than DS_FLAG_CI_DATASET and DS_FLAG_INCONSISTENT
when cloning.  This prevents DS_FLAG_DEFER_DESTROY being inherited from a
clone that is marked for deferred destroy, which causes snapshots of the
clone being destroyed when getting a hold or clone.

Illumos issue:
    5150 zfs clone of a defer_destroy snapshot causes strangeness
MFC r273093, r273096:

r273093:
  Merge the following from ^/projects/release-vmimage:
  r272436, r272437, r272792:

  r272436:
    Remove the first argument to panic(), which was initially
    intended to be the exit code, however when a non-zero exit
    code was returned to release/Makefile, this would prevent
    any remaining (and possibly successful) stages from being
    attempted.

  r272437:

    If the vm-base target fails, prevent the vm-image target
    from being run since it cannot possibly succeed.

  r272792:

    Add /usr/local/bin and /usr/local/sbin to PATH, needed
    if third-party software needs to use utilities outside
    of the base system during post-install stages (indexinfo
    is one culprit).

r273096:
  Merge the following from ^/projects/release-vmimage:
  r273076, r273077, r273079, r273095:

  r273076:
    Add a separate make(1) target to release/Makefile to
    build FreeBSD virtual machine disk images for use on
    the Microsoft Azure service.

    For now, this target is not directly connected to the
    build, however can be manually invoked.

    The 'vm-azure' target invokes {amd64,i386}/mk-azure.sh,
    which does the heavy lifting to produce proper VHDs.
    mk-azure.sh uses a configuration file, defaulting to
    tools/azure.conf if otherwise unset.

  r273077:
    Clear VM_RC_LIST.

  r273079:
    Fix signal list to trigger umount(8).

  r273095:
    Output an informational message when mkimg(1) runs, so it
    does not appear that the process has stopped while waiting
    for a 'y/n' response when waagent is deprovisioned.

Relnotes:	yes
Sponsored by:	The FreeBSD Foundation