Add "compatibility" property for zpool feature sets

Property to allow sets of features to be specified; for compatibility
with specific versions / releases / external systems. Influences
the behavior of 'zpool upgrade' and 'zpool create'. Initial man
page changes and test cases included.

Brief synopsis:

zpool create -o compatibility=off|legacy|file[,file...] pool vdev...

compatibility = off : disable compatibility mode (enable all features)
compatibility = legacy : request that no features be enabled
compatibility = file[,file...] : read features from specified files.
Only features present in *all* files will be enabled on the
resulting pool. Filenames may be absolute, or relative to
/etc/zfs/compatibility.d or /usr/share/zfs/compatibility.d (/etc
checked first).

Only affects zpool create, zpool upgrade and zpool status.

ABI changes in libzfs:

* New function "zpool_load_compat" to load and parse compat sets.
* Add "zpool_compat_status_t" typedef for compatibility parse status.
* Add ZPOOL_PROP_COMPATIBILITY to the pool properties enum
* Add ZPOOL_STATUS_COMPATIBILITY_ERR to the pool status enum

An initial set of base compatibility sets are included in
cmd/zpool/compatibility.d, and the Makefile for cmd/zpool is
modified to install these in $pkgdatadir/compatibility.d and to
create symbolic links to a reasonable set of aliases.

Reviewed-by: ericloewe
Reviewed-by: Matthew Ahrens <[email protected]>
Reviewed-by: Richard Laager <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Colm Buckley <[email protected]>
Closes #11468 

2 files changed, 34 insertions, 0 deletions

diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 56354a107..5170c9ca2 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -32,6 +32,7 @@
  * Copyright (c) 2017, 2019, Datto Inc. All rights reserved.
  * Copyright 2017 Joyent, Inc.
  * Copyright (c) 2017, Intel Corporation.
+ * Copyright (c) 2021, Colm Buckley <[email protected]>
  */
 
 /*
@@ -377,6 +378,11 @@ spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
 		    0, ZPROP_SRC_LOCAL);
 	}
 
+	if (spa->spa_compatibility != NULL) {
+		spa_prop_add_list(*nvp, ZPOOL_PROP_COMPATIBILITY,
+		    spa->spa_compatibility, 0, ZPROP_SRC_LOCAL);
+	}
+
 	if (spa->spa_root != NULL)
 		spa_prop_add_list(*nvp, ZPOOL_PROP_ALTROOT, spa->spa_root,
 		    0, ZPROP_SRC_LOCAL);
@@ -1669,6 +1675,10 @@ spa_unload(spa_t *spa)
 		spa_strfree(spa->spa_comment);
 		spa->spa_comment = NULL;
 	}
+	if (spa->spa_compatibility != NULL) {
+		spa_strfree(spa->spa_compatibility);
+		spa->spa_compatibility = NULL;
+	}
 
 	spa_config_exit(spa, SCL_ALL, spa);
 }
@@ -3249,6 +3259,7 @@ spa_ld_parse_config(spa_t *spa, spa_import_type_t type)
 	vdev_t *rvd;
 	uint64_t pool_guid;
 	char *comment;
+	char *compatibility;
 
 	/*
 	 * Versioning wasn't explicitly added to the label until later, so if
@@ -3297,6 +3308,11 @@ spa_ld_parse_config(spa_t *spa, spa_import_type_t type)
 	if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMMENT, &comment) == 0)
 		spa->spa_comment = spa_strdup(comment);
 
+	ASSERT(spa->spa_compatibility == NULL);
+	if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMPATIBILITY,
+	    &compatibility) == 0)
+		spa->spa_compatibility = spa_strdup(compatibility);
+
 	(void) nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG,
 	    &spa->spa_config_txg);
 
@@ -8668,6 +8684,20 @@ spa_sync_props(void *arg, dmu_tx_t *tx)
 			spa_history_log_internal(spa, "set", tx,
 			    "%s=%s", nvpair_name(elem), strval);
 			break;
+		case ZPOOL_PROP_COMPATIBILITY:
+			strval = fnvpair_value_string(elem);
+			if (spa->spa_compatibility != NULL)
+				spa_strfree(spa->spa_compatibility);
+			spa->spa_compatibility = spa_strdup(strval);
+			/*
+			 * Dirty the configuration on vdevs as above.
+			 */
+			if (tx->tx_txg != TXG_INITIAL)
+				vdev_config_dirty(spa->spa_root_vdev);
+			spa_history_log_internal(spa, "set", tx,
+			    "%s=%s", nvpair_name(elem), strval);
+			break;
+
 		default:
 			/*
 			 * Set pool property values in the poolprops mos object.
diff --git a/module/zfs/spa_config.c b/module/zfs/spa_config.c
index dacba127d..4a3144313 100644
--- a/module/zfs/spa_config.c
+++ b/module/zfs/spa_config.c
@@ -24,6 +24,7 @@
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
  * Copyright (c) 2011, 2020 by Delphix. All rights reserved.
  * Copyright 2017 Joyent, Inc.
+ * Copyright (c) 2021, Colm Buckley <[email protected]>
  */
 
 #include <sys/spa.h>
@@ -446,6 +447,9 @@ spa_config_generate(spa_t *spa, vdev_t *vd, uint64_t txg, int getstats)
 	if (spa->spa_comment != NULL)
 		fnvlist_add_string(config, ZPOOL_CONFIG_COMMENT,
 		    spa->spa_comment);
+	if (spa->spa_compatibility != NULL)
+		fnvlist_add_string(config, ZPOOL_CONFIG_COMPATIBILITY,
+		    spa->spa_compatibility);
 
 	hostid = spa_get_hostid(spa);
 	if (hostid != 0)