Add option none to zfs redundant_metadata property

Currently, additional/extra copies are created for metadata in
addition to the redundancy provided by the pool(mirror/raidz/draid),
due to this 2 times more space is utilized per inode and this decreases
the total number of inodes that can be created in the filesystem. By
setting redundant_metadata to none, no additional copies of metadata
are created, hence can reduce the space consumed by the additional
metadata copies and increase the total number of inodes that can be
created in the filesystem.

Reviewed-by: Dipak Ghosh <dipak.ghosh@hpe.com>
Signed-off-by: Akash B <akash-b@hpe.com>

Author: akashb-22

include/sys/fs/zfs.h

@@ -500,7 +500,8 @@ typedef enum {
 
 typedef enum {
 	ZFS_REDUNDANT_METADATA_ALL,
-	ZFS_REDUNDANT_METADATA_MOST
+	ZFS_REDUNDANT_METADATA_MOST,
+	ZFS_REDUNDANT_METADATA_NONE
 } zfs_redundant_metadata_type_t;
 
 typedef enum {

man/man7/zfsprops.7

@@ -1444,7 +1444,7 @@ affects only files created afterward; existing files are unaffected.
 .Pp
 This property can also be referred to by its shortened column name,
 .Sy recsize .
-.It Sy redundant_metadata Ns = Ns Sy all Ns | Ns Sy most
+.It Sy redundant_metadata Ns = Ns Sy all Ns | Ns Sy most Ns | Ns Sy none
 Controls what types of metadata are stored redundantly.
 ZFS stores an extra copy of metadata, so that if a single block is corrupted,
 the amount of user data lost is limited.
@@ -1485,6 +1485,10 @@ of user data can be lost if a single on-disk block is corrupt.
 The exact behavior of which metadata blocks are stored redundantly may change in
 future releases.
 .Pp
+When set to
+.Sy none ,
+ZFS does not store any copies of metadata redundantly through this property.
+.Pp
 The default value is
 .Sy all .
 .It Sy refquota Ns = Ns Ar size Ns | Ns Sy none

module/zcommon/zfs_prop.c

@@ -369,6 +369,7 @@ zfs_prop_init(void)
 	static const zprop_index_t redundant_metadata_table[] = {
 		{ "all",	ZFS_REDUNDANT_METADATA_ALL },
 		{ "most",	ZFS_REDUNDANT_METADATA_MOST },
+		{ "none",	ZFS_REDUNDANT_METADATA_NONE },
 		{ NULL }
 	};
 
@@ -388,7 +389,7 @@ zfs_prop_init(void)
 	zprop_register_index(ZFS_PROP_REDUNDANT_METADATA, "redundant_metadata",
 	    ZFS_REDUNDANT_METADATA_ALL,
 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
-	    "all | most", "REDUND_MD",
+	    "all | most | none", "REDUND_MD",
 	    redundant_metadata_table, sfeatures);
 	zprop_register_index(ZFS_PROP_SYNC, "sync", ZFS_SYNC_STANDARD,
 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,

module/zfs/dmu_objset.c

@@ -287,7 +287,8 @@ redundant_metadata_changed_cb(void *arg, uint64_t newval)
 	 * Inheritance and range checking should have been done by now.
 	 */
 	ASSERT(newval == ZFS_REDUNDANT_METADATA_ALL ||
-	    newval == ZFS_REDUNDANT_METADATA_MOST);
+	    newval == ZFS_REDUNDANT_METADATA_MOST ||
+	    newval == ZFS_REDUNDANT_METADATA_NONE);
 
 	os->os_redundant_metadata = newval;
 }