OpenZFS 9318 - vol_volsize_to_reservation does not account for raidz skip blocks

When a volume is created in a pool with raidz vdevs and
volblocksize != 128k, the volume can reference more space than is
reserved with the automatically calculated refreservation.  There
are two deficiencies in vol_volsize_to_reservation that contribute
to this:

  1) Skip blocks may be added to keep each allocation a multiple
     of parity + 1. This is the dominating factor when volblocksize
     is close to 2^ashift.

  2) raidz deflation for 128 KB blocks is different for most other
     block sizes.

See "The theory of raidz space accounting" comment in
libzfs_dataset.c for a full explanation.

Authored by: Mike Gerdts <mike.gerdts@joyent.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Kody Kantor <kody.kantor@joyent.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Dan McDonald <danmcd@joyent.com>
Ported-by: Mike Gerdts <mike.gerdts@joyent.com>

Porting Notes:
* ZTS: wait for zvols to exist before writing
* ZTS: use log_must_busy with {zpool|zfs} destroy

OpenZFS-issue: https://www.illumos.org/issues/9318
OpenZFS-commit: https://github.com/illumos/illumos-gate/commit/b73ccab0
Closes #8973

cmd/zfs/zfs_main.c

@@ -29,6 +29,7 @@
  * Copyright 2016 Nexenta Systems, Inc.
  * Copyright (c) 2019 Datto Inc.
  * Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>
+ * Copyright 2019 Joyent, Inc.
  */
 
 #include <assert.h>
@@ -992,10 +993,11 @@ zfs_do_create(int argc, char **argv)
 			zpool_close(zpool_handle);
 			goto error;
 		}
-		zpool_close(zpool_handle);
 
-		volsize = zvol_volsize_to_reservation(volsize, real_props);
+		volsize = zvol_volsize_to_reservation(zpool_handle, volsize,
+		    real_props);
 		nvlist_free(real_props);
+		zpool_close(zpool_handle);
 
 		if (nvlist_lookup_string(props, zfs_prop_to_name(resv_prop),
 		    &strval) != 0) {