Add compatibility file for GRUB versions up to v2.06

GRUB is not able to detect ZFS pool if snaphsot of top level boot
pool is created. This issue is observed with GRUB versions up to
v2.06 if extensible_dataset feature is enabled on ZFS boot pool.

compatibility=grub2-2.06 would enable all read-only compatible
zpool features except extensible_dataset and other features that
depend on it.

The existing grub2 compatibility file lists all read-only features
that can be enabled on boot pool for grub with version 2.12
onwards.

Signed-off-by: Umer Saleem <usaleem@ixsystems.com>

cmd/zpool/Makefile.am

@@ -141,6 +141,7 @@ dist_zpoolcompat_DATA = \
 	%D%/compatibility.d/freebsd-11.3 \
 	%D%/compatibility.d/freenas-9.10.2 \
 	%D%/compatibility.d/grub2 \
+	%D%/compatibility.d/grub2-2.06 \
 	%D%/compatibility.d/openzfs-2.0-freebsd \
 	%D%/compatibility.d/openzfs-2.0-linux \
 	%D%/compatibility.d/openzfs-2.1-freebsd \

cmd/zpool/compatibility.d/grub2

@@ -1,4 +1,4 @@
-# Features which are supported by GRUB2
+# Features which are supported by GRUB2 versions from v2.12 onwards.
 allocation_classes
 async_destroy
 block_cloning

cmd/zpool/compatibility.d/grub2-2.06

@@ -0,0 +1,23 @@
+# Features which are supported by GRUB2 versions prior to v2.12.
+#
+# GRUB is not able to detect ZFS pool if snaphsot of top level boot pool
+# is created. This issue is observed with GRUB versions before v2.12 if
+# extensible_dataset feature is enabled on ZFS boot pool.
+#
+# This file lists all read-only comaptible features except
+# extensible_dataset and any other feature that depends on it.
+#
+allocation_classes
+async_destroy
+block_cloning
+device_rebuild
+embedded_data
+empty_bpobj
+enabled_txg
+hole_birth
+log_spacemap
+lz4_compress
+resilver_defer
+spacemap_histogram
+spacemap_v2
+zpool_checkpoint

man/man7/zpool-features.7

@@ -218,7 +218,7 @@ to the end of the line is ignored.
 .Sy Example :
 .Bd -literal -compact -offset 4n
 .No example# Nm cat Pa /usr/share/zfs/compatibility.d/grub2
-# Features which are supported by GRUB2
+# Features which are supported by GRUB2 versions from v2.12 onwards.
 allocation_classes
 async_destroy
 block_cloning
@@ -242,6 +242,31 @@ userobj_accounting
 zilsaxattr
 zpool_checkpoint
 
+.No example# Nm cat Pa /usr/share/zfs/compatibility.d/grub2-2.06
+# Features which are supported by GRUB2 versions prior to v2.12.
+#
+# GRUB is not able to detect ZFS pool if snaphsot of top level boot pool
+# is created. This issue is observed with GRUB versions before v2.12 if
+# extensible_dataset feature is enabled on ZFS boot pool.
+#
+# This file lists all read-only comaptible features except
+# extensible_dataset and any other feature that depends on it.
+#
+allocation_classes
+async_destroy
+block_cloning
+device_rebuild
+embedded_data
+empty_bpobj
+enabled_txg
+hole_birth
+log_spacemap
+lz4_compress
+resilver_defer
+spacemap_histogram
+spacemap_v2
+zpool_checkpoint
+
 .No example# Nm zpool Cm create Fl o Sy compatibility Ns = Ns Ar grub2 Ar bootpool Ar vdev
 .Ed
 .Pp
@@ -666,7 +691,7 @@ are destroyed.
 Large dnodes allow more data to be stored in the bonus buffer,
 thus potentially improving performance by avoiding the use of spill blocks.
 .
-.feature com.delphix livelist yes
+.feature com.delphix livelist yes extensible_dataset
 This feature allows clones to be deleted faster than the traditional method
 when a large number of random/sparse writes have been made to the clone.
 All blocks allocated and freed after a clone is created are tracked by the

tests/zfs-tests/tests/functional/cli_root/zpool_create/zpool_create.shlib

@@ -119,9 +119,8 @@ function check_feature_set
 	while read line; do
 		typeset flag=1
 
-		if [[ "$line" == "#*" ]]; then
-			continue
-		fi
+		# Skip comments
+		[[ $line = \#* ]] && continue
 
 		for set in "$@"; do
 			if ! grep -q "$line" $ZPOOL_COMPAT_DIR/$set; then