fix some assign arc buf with brt clone and O_TRUNC

module/zfs/dbuf.c

@@ -2945,7 +2945,8 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx)
 	while (db->db_state == DB_READ || db->db_state == DB_FILL)
 		cv_wait(&db->db_changed, &db->db_mtx);
 
-	ASSERT(db->db_state == DB_CACHED || db->db_state == DB_UNCACHED);
+	ASSERT(db->db_state == DB_CACHED || db->db_state == DB_UNCACHED ||
+	    db->db_state == DB_NOFILL);
 
 	if (db->db_state == DB_CACHED &&
 	    zfs_refcount_count(&db->db_holds) - 1 > db->db_dirtycnt) {
@@ -2982,7 +2983,17 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx)
 			arc_buf_destroy(db->db_buf, db);
 		}
 		db->db_buf = NULL;
+	} else if (db->db_state == DB_NOFILL) {
+		/*
+		 * We will be completely replacing the cloned block.  In case
+		 * it was cloned in this transaction group, let's undirty the
+		 * pending clone and mark the block as uncached. This will be
+		 * as if the clone was never done.
+		 */
+		VERIFY(!dbuf_undirty(db, tx));
+		db->db_state = DB_UNCACHED;
 	}
+
 	ASSERT(db->db_buf == NULL);
 	dbuf_set_data(db, buf);
 	db->db_state = DB_FILL;

tests/runfiles/linux.run

@@ -44,7 +44,8 @@ tests = ['block_cloning_copyfilerange', 'block_cloning_copyfilerange_partial',
     'block_cloning_copyfilerange_cross_dataset',
     'block_cloning_cross_enc_dataset',
     'block_cloning_copyfilerange_fallback_same_txg',
-    'block_cloning_replay', 'block_cloning_replay_encrypted']
+    'block_cloning_replay', 'block_cloning_replay_encrypted',
+    'block_cloning_ficlone_and_write']
 tags = ['functional', 'block_cloning']
 
 [tests/functional/chattr:Linux]

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

@@ -311,6 +311,8 @@ elif sys.platform.startswith('linux'):
             ['SKIP', cfr_cross_reason],
         'block_cloning/block_cloning_cross_enc_dataset':
             ['SKIP', cfr_cross_reason],
+        'block_cloning/block_cloning_ficlone_and_write':
+            ['SKIP', cfr_reason],
     })
 
 # Not all Github actions runners have scsi_debug module, so we may skip

tests/zfs-tests/tests/Makefile.am

@@ -454,6 +454,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/block_cloning/block_cloning_cross_enc_dataset.ksh \
 	functional/block_cloning/block_cloning_replay.ksh \
 	functional/block_cloning/block_cloning_replay_encrypted.ksh \
+	functional/block_cloning/block_cloning_ficlone_and_write.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_ficlone_and_write.ksh

@@ -0,0 +1,80 @@
+#!/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
+#
+
+#
+# Copyright (c) 2023, Kay Pedersen <mail@mkwg.de>
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/block_cloning/block_cloning.kshlib
+
+verify_runnable "global"
+
+if [[ $(linux_version) -lt $(linux_version "4.5") ]]; then
+  log_unsupported "copy_file_range not available before Linux 4.5"
+fi
+
+claim="O_TRUNC, writing and FICLONE to a large (>4G) file shouldn't fail"
+
+log_assert $claim
+
+NO_LOOP_BREAK=true
+
+function cleanup
+{
+    datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+}
+
+function loop
+{
+    while $NO_LOOP_BREAK; do clonefile -c -t -q /$TESTPOOL/file /$TESTPOOL/clone; done
+}
+
+log_onexit cleanup
+
+log_must zpool create -o feature@block_cloning=enabled $TESTPOOL $DISKS
+
+log_must dd if=/dev/urandom of=/$TESTPOOL/file bs=1M count=4000
+log_must sync_pool $TESTPOOL
+
+
+log_note "Copying entire file with FICLONE"
+
+log_must clonefile -c /$TESTPOOL/file /$TESTPOOL/clone
+log_must sync_pool $TESTPOOL
+
+log_must have_same_content /$TESTPOOL/file /$TESTPOOL/clone
+
+log_note "looping a clone"
+loop &
+
+log_must dd if=/dev/urandom of=/$TESTPOOL/clone bs=1M count=4000
+log_must dd if=/dev/urandom of=/$TESTPOOL/clone bs=1M count=4000
+
+NO_LOOP_BREAK=false
+
+# just to be sure all background jobs are killed.
+log_must kill $(jobs -p)
+
+log_must sync_pool $TESTPOOL
+
+log_pass $claim