Fix false assertion in dmu_tx_dirty_buf() on cloning

module/zfs/dmu_tx.c

@@ -800,6 +800,14 @@ dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db)
 			case THT_CLONE:
 				if (blkid >= beginblk && blkid <= endblk)
 					match_offset = TRUE;
+				/*
+				 * They might have to increase nlevels,
+				 * thus dirtying the new TLIBs.  Or the
+				 * might have to change the block size,
+				 * thus dirying the new lvl=0 blk=0.
+				 */
+				if (blkid == 0)
+					match_offset = TRUE;
 				break;
 			default:
 				cmn_err(CE_PANIC, "bad txh_type %d",

tests/runfiles/common.run

@@ -82,7 +82,7 @@ tests = ['block_cloning_clone_mmap_cached',
     'block_cloning_copyfilerange_fallback_same_txg',
     'block_cloning_replay', 'block_cloning_replay_encrypted',
     'block_cloning_lwb_buffer_overflow', 'block_cloning_clone_mmap_write',
-    'block_cloning_rlimit_fsize']
+    'block_cloning_rlimit_fsize', 'block_cloning_large_offset']
 tags = ['functional', 'block_cloning']
 
 [tests/functional/bootfs]

tests/test-runner/bin/zts-report.py.in

@@ -339,6 +339,8 @@ elif sys.platform.startswith('linux'):
             ['SKIP', cfr_reason],
         'block_cloning/block_cloning_rlimit_fsize':
             ['SKIP', cfr_reason],
+        'block_cloning/block_cloning_large_offset':
+            ['SKIP', cfr_reason],
         'cli_root/zfs_rename/zfs_rename_002_pos': ['FAIL', known_reason],
         'cli_root/zpool_reopen/zpool_reopen_003_pos': ['FAIL', known_reason],
         'cp_files/cp_files_002_pos': ['SKIP', cfr_reason],

tests/zfs-tests/tests/Makefile.am

@@ -482,6 +482,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/block_cloning/block_cloning_replay_encrypted.ksh \
 	functional/block_cloning/block_cloning_lwb_buffer_overflow.ksh \
 	functional/block_cloning/block_cloning_rlimit_fsize.ksh \
+	functional/block_cloning/block_cloning_large_offset.ksh \
 	functional/bootfs/bootfs_001_pos.ksh \
 	functional/bootfs/bootfs_002_neg.ksh \
 	functional/bootfs/bootfs_003_pos.ksh \

tests/zfs-tests/tests/functional/block_cloning/block_cloning_large_offset.ksh

@@ -0,0 +1,83 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or https://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/block_cloning/block_cloning.kshlib
+
+#
+# DESCRIPTION:
+#	Verify that cloning a file at a large offset is possible.
+#
+# STRATEGY:
+#   1. Create dataset.
+#   2. Populate the source file with 1024 blocks at 1024 block offset.
+#   3. Clone 1024 blocks at a 1024-block offset.
+#   4. Compare the cloned file with the original file.
+#
+
+verify_runnable "global"
+
+if is_linux && [[ $(linux_version) -lt $(linux_version "4.5") ]]; then
+  log_unsupported "copy_file_range not available before Linux 4.5"
+fi
+
+claim="The first clone at a large offset is functional"
+
+log_assert $claim
+
+function cleanup
+{
+	datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+}
+
+log_onexit cleanup
+
+#
+# 1. Create dataset.
+#
+log_must zpool create -o feature@block_cloning=enabled $TESTPOOL $DISKS
+sync_pool $TESTPOOL
+
+#
+# 2. Populate the source file with 1024 blocks at 1024 block offset.
+#
+log_must dd if=/dev/urandom of=/$TESTPOOL/file1 \
+    oflag=sync bs=128k count=1024 seek=1024
+sync_pool $TESTPOOL
+
+#
+# 3. Clone 1024 blocks at a 1024-block offset.
+#
+log_must clonefile -f /$TESTPOOL/file1 /$TESTPOOL/file2 134217728 134217728 \
+    134217728
+sync_pool $TESTPOOL
+
+#
+# 4. Compare the cloned file with the original file.
+#
+log_must have_same_content /$TESTPOOL/file1 /$TESTPOOL/file2
+typeset blocks=$(get_same_blocks $TESTPOOL file1 $TESTPOOL file2)
+
+# FreeBSD's seq(1) leaves a trailing space, remove it with sed(1).
+log_must [ "$blocks" = "$(seq -s " " 0 1023 | sed 's/ $//')" ]
+
+log_pass $claim