9286 want refreservation=auto

@@ -741,11 +741,11 @@
        Limits the amount of space a dataset can consume.  This property
        enforces a hard limit on the amount of space used.  This hard limit
        does not include space used by descendents, including file systems and
        snapshots.
 
-     refreservation=size|none
+     refreservation=size|none|auto
        The minimum amount of space guaranteed to a dataset, not including its
        descendents.  When the amount of space used is below this value, the
        dataset is treated as if it were taking up the amount of space
        specified by refreservation.  The refreservation reservation is
        accounted for in the parent datasets' space used, and counts against

@@ -753,21 +753,30 @@
 
        If refreservation is set, a snapshot is only allowed if there is enough
        free pool space outside of this reservation to accommodate the current
        number of "referenced" bytes in the dataset.
 
+       If refreservation is set to auto, a volume is made dense (or "not
+       sparse").  refreservation=auto is only supported on volumes. See
+       volsize in the Native Properties section for more information about
+       sparse volumes.
+
        This property can also be referred to by its shortened column name,
        refreserv.
 
-     reservation=size|none
+     reservation=size|none|auto
        The minimum amount of space guaranteed to a dataset and its
        descendants.  When the amount of space used is below this value, the
        dataset is treated as if it were taking up the amount of space
        specified by its reservation.  Reservations are accounted for in the
        parent datasets' space used, and count against the parent datasets'
        quotas and reservations.
 
+       See refreservation=auto above for a description of the behavior of
+       setting reservation to auto.  If the pool is at version 9 or later,
+       refreservation=auto should be used instead.
+
        This property can also be referred to by its shortened column name,
        reserv.
 
      secondarycache=all|none|metadata
        Controls what is cached in the secondary cache (L2ARC).  If this

@@ -878,13 +887,15 @@
 
        Though not recommended, a "sparse volume" (also known as "thin
        provisioning") can be created by specifying the -s option to the zfs
        create -V command, or by changing the reservation after the volume has
        been created.  A "sparse volume" is a volume where the reservation is
-       less then the volume size.  Consequently, writes to a sparse volume can
-       fail with ENOSPC when the pool is low on space.  For a sparse volume,
-       changes to volsize are not reflected in the reservation.
+       less than the size of the volume plus the space required to store its
+       metadata.  Consequently, writes to a sparse volume can fail with ENOSPC
+       when the pool is low on space.  For a sparse volume, changes to volsize
+       are not reflected in the reservation.  A sparse volume can be made
+       dense (or "not sparse") by setting the reservation to auto.
 
      vscan=on|off
        Controls whether regular files should be scanned for viruses when a
        file is opened and closed.  In addition to enabling this property, the
        virus scan service must also be enabled for virus scanning to occur.