OpenZFS 8906 - uts: illumos rootfs should support salted cksum

Porting notes:
* As of grub-2.02 these checksums are not supported.  However, as
  pointed out in openzfs#6501 there are alternatives such as EFISTUB which
  work and have no such restriction.  A warning was added to the
  checksum property section of the zfs.8 man page.

Authored by: Toomas Soome <tsoome@me.com>
Reviewed by: C Fraire <cfraire@me.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Yuri Pankov <yuripv@yuripv.net>
Approved by: Dan McDonald <danmcd@joyent.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://illumos.org/issues/8906
OpenZFS-commit: openzfs/openzfs@7dec52f
Closes openzfs#6501
Closes openzfs#7714

man/man5/zpool-features.5

@@ -14,7 +14,7 @@
 .\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
 .\" own identifying information:
 .\" Portions Copyright [yyyy] [name of copyright owner]
-.TH ZPOOL-FEATURES 5 "Aug 27, 2013"
+.TH ZPOOL-FEATURES 5 "Jun 8, 2018"
 .SH NAME
 zpool\-features \- ZFS pool feature descriptions
 .SH DESCRIPTION
@@ -248,8 +248,9 @@ immediately activate the \fBlz4_compress\fR feature on the underlying
 pool using the \fBzfs\fR(1M) command. Also, all newly written metadata
 will be compressed with \fBlz4\fR algorithm. Since this feature is not
 read-only compatible, this operation will render the pool unimportable
-on systems without support for the \fBlz4_compress\fR feature. Booting
-off of \fBlz4\fR-compressed root pools is supported.
+on systems without support for the \fBlz4_compress\fR feature.
+
+Booting off of \fBlz4\fR-compressed root pools is supported.
 
 This feature becomes \fBactive\fR as soon as it is enabled and will
 never return to being \fBenabled\fB.
@@ -510,8 +511,7 @@ can turn on the \fBsha512\fR checksum on any dataset using the
 and will return to being \fBenabled\fR once all filesystems that have
 ever had their checksum set to \fBsha512\fR are destroyed.
 
-Booting off of pools utilizing SHA-512/256 is supported (provided that
-the updated GRUB stage2 module is installed).
+Booting off of pools utilizing SHA-512/256 is supported.
 
 .RE
 
@@ -545,9 +545,7 @@ can turn on the \fBskein\fR checksum on any dataset using the
 and will return to being \fBenabled\fR once all filesystems that have
 ever had their checksum set to \fBskein\fR are destroyed.
 
-Booting off of pools using \fBskein\fR is \fBNOT\fR supported
--- any attempt to enable \fBskein\fR on a root pool will fail with an
-error.
+Booting off of pools using \fBskein\fR is supported.
 
 .RE
 
@@ -587,9 +585,7 @@ can turn on the \fBedonr\fR checksum on any dataset using the
 and will return to being \fBenabled\fR once all filesystems that have
 ever had their checksum set to \fBedonr\fR are destroyed.
 
-Booting off of pools using \fBedonr\fR is \fBNOT\fR supported
--- any attempt to enable \fBedonr\fR on a root pool will fail with an
-error.
+Booting off of pools using \fBedonr\fR is supported.
 
 .RE
 

man/man8/zfs.8

@@ -29,7 +29,7 @@
 .\" Copyright 2016 Nexenta Systems, Inc.
 .\" Copyright 2016 Richard Laager. All rights reserved.
 .\"
-.Dd June 28, 2017
+.Dd July 13, 2018
 .Dt ZFS 8 SMM
 .Os Linux
 .Sh NAME
@@ -1049,6 +1049,9 @@ The
 and
 .Sy edonr
 checksum algorithms require enabling the appropriate features on the pool.
+These algorithms are not supported by GRUB and should not be set on the
+.Sy bootfs
+filesystem when using GRUB to boot the system.
 Please see
 .Xr zpool-features 5
 for more information on these algorithms.

module/zfs/zfs_ioctl.c

@@ -3985,16 +3985,7 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 
 		if ((err = spa_open(dsname, &spa, FTAG)) != 0)
 			return (err);
-		/*
-		 * Salted checksums are not supported on root pools.
-		 */
-		if (spa_bootfs(spa) != 0 &&
-		    intval < ZIO_CHECKSUM_FUNCTIONS &&
-		    (zio_checksum_table[intval].ci_flags &
-		    ZCHECKSUM_FLAG_SALTED)) {
-			spa_close(spa, FTAG);
-			return (SET_ERROR(ERANGE));
-		}
+
 		if (!spa_feature_is_enabled(spa, feature)) {
 			spa_close(spa, FTAG);
 			return (SET_ERROR(ENOTSUP));