BRT: Fix ZAP entry endianness

During original block cloning implementation a mistake was made,
making BRT ZAP entries an array of 8 1-byte entries instead of 1
entry of 8 bytes. This makes the pools non-endian-safe.

This commit introduces a new read-compatible pool feature
"com.truenas:block_cloning_endian", fixing the endianness issue
for new pools while maintaining compatibility with existing ones.

The feature is automatically activated when creating the first BRT
ZAP (ensuring we don't activate it on pools that already have BRT
entries in the old format).  When active, BRT entries are stored
as single 8-byte values.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <alexander.motin@TrueNAS.com>
Closes #17572

include/zfeature_common.h

@@ -88,6 +88,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_LONGNAME,
 	SPA_FEATURE_LARGE_MICROZAP,
 	SPA_FEATURE_DYNAMIC_GANG_HEADER,
+	SPA_FEATURE_BLOCK_CLONING_ENDIAN,
 	SPA_FEATURES
 } spa_feature_t;
 

lib/libzfs/libzfs.abi

@@ -638,7 +638,7 @@
     <elf-symbol name='fletcher_4_superscalar_ops' size='128' 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='2520' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='spa_feature_table' size='2576' 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='528' 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'/>
@@ -6397,7 +6397,8 @@
       <enumerator name='SPA_FEATURE_LONGNAME' value='42'/>
       <enumerator name='SPA_FEATURE_LARGE_MICROZAP' value='43'/>
       <enumerator name='SPA_FEATURE_DYNAMIC_GANG_HEADER' value='44'/>
-      <enumerator name='SPA_FEATURES' value='45'/>
+      <enumerator name='SPA_FEATURE_BLOCK_CLONING_ENDIAN' value='45'/>
+      <enumerator name='SPA_FEATURES' value='46'/>
     </enum-decl>
     <typedef-decl name='spa_feature_t' type-id='33ecb627' id='d6618c78'/>
     <qualified-type-def type-id='80f4b756' const='yes' id='b99c00c9'/>
@@ -9604,8 +9605,8 @@
     </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='20160' id='b948da70'>
+    <array-type-def dimensions='1' type-id='83f29ca2' size-in-bits='20608' id='b9408bab'>
-      <subrange length='45' type-id='7359adad' id='cb8ddca0'/>
+      <subrange length='46' type-id='7359adad' id='8b86bc1b'/>
     </array-type-def>
     <enum-decl name='zfeature_flags' id='6db816a4'>
       <underlying-type type-id='9cac1fee'/>
@@ -9683,7 +9684,7 @@
     <pointer-type-def type-id='611586a1' size-in-bits='64' id='2e243169'/>
     <qualified-type-def type-id='eaa32e2f' const='yes' id='83be723c'/>
     <pointer-type-def type-id='83be723c' size-in-bits='64' id='7acd98a2'/>
-    <var-decl name='spa_feature_table' type-id='b948da70' mangled-name='spa_feature_table' visibility='default' elf-symbol-id='spa_feature_table'/>
+    <var-decl name='spa_feature_table' type-id='b9408bab' mangled-name='spa_feature_table' visibility='default' elf-symbol-id='spa_feature_table'/>
     <var-decl name='zfeature_checks_disable' type-id='c19b74c3' mangled-name='zfeature_checks_disable' visibility='default' elf-symbol-id='zfeature_checks_disable'/>
     <function-decl name='opendir' visibility='default' binding='global' size-in-bits='64'>
       <parameter type-id='80f4b756'/>

man/man7/zpool-features.7

@@ -401,6 +401,17 @@ This feature becomes
 .Sy active
 when first block is cloned.
 When the last cloned block is freed, it goes back to the enabled state.
+.feature com.truenas block_cloning_endian yes
+This feature corrects ZAP entry endianness issues in the Block Reference
+Table (BRT) used by block cloning.
+During the original block cloning implementation, BRT ZAP entries were
+mistakenly stored as arrays of 8 single-byte entries instead of single
+8-byte entries, making pools non-endian-safe.
+.Pp
+This feature is activated when the first BRT ZAP is created (that way
+ensuring compatibility with existing pools).
+When active, new BRT entries are stored in the correct endian-safe format.
+The feature becomes inactive when all BRT ZAPs are destroyed.
 .feature com.delphix bookmarks yes extensible_dataset
 This feature enables use of the
 .Nm zfs Cm bookmark

module/zcommon/zfeature_common.c

@@ -732,6 +732,12 @@ zpool_feature_init(void)
 	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
 	    sfeatures);
 
+	zfeature_register(SPA_FEATURE_BLOCK_CLONING_ENDIAN,
+	    "com.truenas:block_cloning_endian", "block_cloning_endian",
+	    "Fixes BRT ZAP endianness on new pools.",
+	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL,
+	    sfeatures);
+
 	zfeature_register(SPA_FEATURE_AVZ_V2,
 	    "com.klarasystems:vdev_zaps_v2", "vdev_zaps_v2",
 	    "Support for root vdev ZAP.",

module/zfs/brt.c

@@ -478,6 +478,18 @@ brt_vdev_create(spa_t *spa, brt_vdev_t *brtvd, dmu_tx_t *tx)
 	    sizeof (uint64_t), 1, &brtvd->bv_mos_brtvdev, tx));
 	BRT_DEBUG("Pool directory object created, object=%s", name);
 
+	/*
+	 * Activate the endian-fixed feature if this is the first BRT ZAP
+	 * (i.e., BLOCK_CLONING is not yet active) and the feature is enabled.
+	 */
+	if (spa_feature_is_enabled(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN) &&
+	    !spa_feature_is_active(spa, SPA_FEATURE_BLOCK_CLONING)) {
+		spa_feature_incr(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN, tx);
+	} else if (spa_feature_is_active(spa,
+	    SPA_FEATURE_BLOCK_CLONING_ENDIAN)) {
+		spa_feature_incr(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN, tx);
+	}
+
 	spa_feature_incr(spa, SPA_FEATURE_BLOCK_CLONING, tx);
 }
 
@@ -658,6 +670,8 @@ brt_vdev_destroy(spa_t *spa, brt_vdev_t *brtvd, dmu_tx_t *tx)
 	rw_exit(&brtvd->bv_lock);
 
 	spa_feature_decr(spa, SPA_FEATURE_BLOCK_CLONING, tx);
+	if (spa_feature_is_active(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN))
+		spa_feature_decr(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN, tx);
 }
 
 static void
@@ -855,16 +869,29 @@ brt_entry_fill(const blkptr_t *bp, brt_entry_t *bre, uint64_t *vdevidp)
 	*vdevidp = DVA_GET_VDEV(&bp->blk_dva[0]);
 }
 
+static boolean_t
+brt_has_endian_fixed(spa_t *spa)
+{
+	return (spa_feature_is_active(spa, SPA_FEATURE_BLOCK_CLONING_ENDIAN));
+}
+
 static int
-brt_entry_lookup(brt_vdev_t *brtvd, brt_entry_t *bre)
+brt_entry_lookup(spa_t *spa, brt_vdev_t *brtvd, brt_entry_t *bre)
 {
 	uint64_t off = BRE_OFFSET(bre);
 
 	if (brtvd->bv_mos_entries == 0)
 		return (SET_ERROR(ENOENT));
 
-	return (zap_lookup_uint64_by_dnode(brtvd->bv_mos_entries_dnode,
+	if (brt_has_endian_fixed(spa)) {
-	    &off, BRT_KEY_WORDS, 1, sizeof (bre->bre_count), &bre->bre_count));
+		return (zap_lookup_uint64_by_dnode(brtvd->bv_mos_entries_dnode,
+		    &off, BRT_KEY_WORDS, sizeof (bre->bre_count), 1,
+		    &bre->bre_count));
+	} else {
+		return (zap_lookup_uint64_by_dnode(brtvd->bv_mos_entries_dnode,
+		    &off, BRT_KEY_WORDS, 1, sizeof (bre->bre_count),
+		    &bre->bre_count));
+	}
 }
 
 /*
@@ -1056,7 +1083,7 @@ brt_entry_decref(spa_t *spa, const blkptr_t *bp)
 	}
 	rw_exit(&brtvd->bv_lock);
 
-	error = brt_entry_lookup(brtvd, &bre_search);
+	error = brt_entry_lookup(spa, brtvd, &bre_search);
 	/* bre_search now contains correct bre_count */
 	if (error == ENOENT) {
 		BRTSTAT_BUMP(brt_decref_no_entry);
@@ -1118,7 +1145,7 @@ brt_entry_get_refcount(spa_t *spa, const blkptr_t *bp)
 	bre = avl_find(&brtvd->bv_tree, &bre_search, NULL);
 	if (bre == NULL) {
 		rw_exit(&brtvd->bv_lock);
-		error = brt_entry_lookup(brtvd, &bre_search);
+		error = brt_entry_lookup(spa, brtvd, &bre_search);
 		if (error == ENOENT) {
 			refcnt = 0;
 		} else {
@@ -1270,10 +1297,18 @@ brt_pending_apply_vdev(spa_t *spa, brt_vdev_t *brtvd, uint64_t txg)
 		uint64_t off = BRE_OFFSET(bre);
 		if (brtvd->bv_mos_entries != 0 &&
 		    brt_vdev_lookup(spa, brtvd, off)) {
-			int error = zap_lookup_uint64_by_dnode(
+			int error;
-			    brtvd->bv_mos_entries_dnode, &off,
+			if (brt_has_endian_fixed(spa)) {
-			    BRT_KEY_WORDS, 1, sizeof (bre->bre_count),
+				error = zap_lookup_uint64_by_dnode(
-			    &bre->bre_count);
+				    brtvd->bv_mos_entries_dnode, &off,
+				    BRT_KEY_WORDS, sizeof (bre->bre_count), 1,
+				    &bre->bre_count);
+			} else {
+				error = zap_lookup_uint64_by_dnode(
+				    brtvd->bv_mos_entries_dnode, &off,
+				    BRT_KEY_WORDS, 1, sizeof (bre->bre_count),
+				    &bre->bre_count);
+			}
 			if (error == 0) {
 				BRTSTAT_BUMP(brt_addref_entry_on_disk);
 			} else {
@@ -1326,7 +1361,7 @@ brt_pending_apply(spa_t *spa, uint64_t txg)
 }
 
 static void
-brt_sync_entry(dnode_t *dn, brt_entry_t *bre, dmu_tx_t *tx)
+brt_sync_entry(spa_t *spa, dnode_t *dn, brt_entry_t *bre, dmu_tx_t *tx)
 {
 	uint64_t off = BRE_OFFSET(bre);
 
@@ -1337,9 +1372,15 @@ brt_sync_entry(dnode_t *dn, brt_entry_t *bre, dmu_tx_t *tx)
 		    BRT_KEY_WORDS, tx);
 		VERIFY(error == 0 || error == ENOENT);
 	} else {
-		VERIFY0(zap_update_uint64_by_dnode(dn, &off,
+		if (brt_has_endian_fixed(spa)) {
-		    BRT_KEY_WORDS, 1, sizeof (bre->bre_count),
+			VERIFY0(zap_update_uint64_by_dnode(dn, &off,
-		    &bre->bre_count, tx));
+			    BRT_KEY_WORDS, sizeof (bre->bre_count), 1,
+			    &bre->bre_count, tx));
+		} else {
+			VERIFY0(zap_update_uint64_by_dnode(dn, &off,
+			    BRT_KEY_WORDS, 1, sizeof (bre->bre_count),
+			    &bre->bre_count, tx));
+		}
 	}
 }
 
@@ -1368,7 +1409,8 @@ brt_sync_table(spa_t *spa, dmu_tx_t *tx)
 
 		void *c = NULL;
 		while ((bre = avl_destroy_nodes(&brtvd->bv_tree, &c)) != NULL) {
-			brt_sync_entry(brtvd->bv_mos_entries_dnode, bre, tx);
+			brt_sync_entry(spa, brtvd->bv_mos_entries_dnode, bre,
+			    tx);
 			kmem_cache_free(brt_entry_cache, bre);
 		}
 

tests/zfs-tests/tests/functional/cli_root/zpool_get/zpool_get.cfg

@@ -115,5 +115,6 @@ if is_linux || is_freebsd; then
 	    "feature@fast_dedup"
 	    "feature@longname"
 	    "feature@large_microzap"
+	    "feature@block_cloning_endian"
 	)
 fi