Implementation of block cloning for ZFS

Block Cloning allows to manually clone a file (or a subset of its
blocks) into another (or the same) file by just creating additional
references to the data blocks without copying the data itself.
Those references are kept in the Block Reference Tables (BRTs).

The whole design of block cloning is documented in module/zfs/brt.c.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Christian Schwarz <christian.schwarz@nutanix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes #13392

lib/libzfs/libzfs.abi

@@ -590,7 +590,7 @@
     <elf-symbol name='fletcher_4_superscalar_ops' size='64' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='libzfs_config_ops' size='16' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='sa_protocol_names' size='16' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
-    <elf-symbol name='spa_feature_table' size='2072' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='spa_feature_table' size='2128' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfeature_checks_disable' size='4' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_deleg_perm_tab' size='512' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_history_event_names' size='328' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
@@ -3174,7 +3174,10 @@
       <enumerator name='ZPOOL_PROP_LOAD_GUID' value='30'/>
       <enumerator name='ZPOOL_PROP_AUTOTRIM' value='31'/>
       <enumerator name='ZPOOL_PROP_COMPATIBILITY' value='32'/>
-      <enumerator name='ZPOOL_NUM_PROPS' value='33'/>
+      <enumerator name='ZPOOL_PROP_BCLONEUSED' value='33'/>
+      <enumerator name='ZPOOL_PROP_BCLONESAVED' value='34'/>
+      <enumerator name='ZPOOL_PROP_BCLONERATIO' value='35'/>
+      <enumerator name='ZPOOL_NUM_PROPS' value='36'/>
     </enum-decl>
     <typedef-decl name='zpool_prop_t' type-id='af1ba157' id='5d0c23fb'/>
     <enum-decl name='vdev_prop_t' naming-typedef-id='5aa5c90c' id='1573bec8'>
@@ -4850,8 +4853,8 @@
     </function-decl>
   </abi-instr>
   <abi-instr address-size='64' path='module/zcommon/zfeature_common.c' language='LANG_C99'>
-    <array-type-def dimensions='1' type-id='83f29ca2' size-in-bits='16576' id='d95b2b0b'>
-      <subrange length='37' type-id='7359adad' id='aa6426fb'/>
+    <array-type-def dimensions='1' type-id='83f29ca2' size-in-bits='17024' id='d95b2b0b'>
+      <subrange length='38' type-id='7359adad' id='aa6426fb'/>
     </array-type-def>
     <enum-decl name='spa_feature' id='33ecb627'>
       <underlying-type type-id='9cac1fee'/>
@@ -4893,7 +4896,8 @@
       <enumerator name='SPA_FEATURE_ZILSAXATTR' value='34'/>
       <enumerator name='SPA_FEATURE_HEAD_ERRLOG' value='35'/>
       <enumerator name='SPA_FEATURE_BLAKE3' value='36'/>
-      <enumerator name='SPA_FEATURES' value='37'/>
+      <enumerator name='SPA_FEATURE_BLOCK_CLONING' value='37'/>
+      <enumerator name='SPA_FEATURES' value='38'/>
     </enum-decl>
     <typedef-decl name='spa_feature_t' type-id='33ecb627' id='d6618c78'/>
     <enum-decl name='zfeature_flags' id='6db816a4'>