OpenZFS 5120 - zfs should allow large block/gzip/raidz boot pool (loader project)

Authored by: Toomas Soome <tsoome@me.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Reviewed by: Andrew Stormont <andyjstormont@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Don Brady <don.brady@intel.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

Porting Notes:
- grub-2.02-beta2-422-gcad5cc0 includes support for large blocks.
- Commit 8aab121 allowed GZIP[1-9].
- Grub allows pools with multiple top-level vdevs.

OpenZFS-issue: https://www.illumos.org/issues/5120
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c8811bd
Closes #6007

module/zfs/zfs_ioctl.c

@@ -30,6 +30,8 @@
  * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
+ * Copyright (c) 2014 Integros [integros.com]
+ * Copyright 2016 Toomas Soome <tsoome@me.com>
  * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  */
 
@@ -3856,16 +3858,6 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 		    intval > SPA_OLD_MAXBLOCKSIZE) {
 			spa_t *spa;
 
-			/*
-			 * If this is a bootable dataset then
-			 * we don't allow large (>128K) blocks,
-			 * because GRUB doesn't support them.
-			 */
-			if (zfs_is_bootfs(dsname) &&
-			    intval > SPA_OLD_MAXBLOCKSIZE) {
-				return (SET_ERROR(ERANGE));
-			}
-
 			/*
 			 * We don't allow setting the property above 1MB,
 			 * unless the tunable has been changed.