zdb: Report bad label checksum

In case if all label checksums will be invalid on any vdev, the pool
will become unimportable. From other side zdb with -l option will not
provide any useful information why it happened. Add notifications
about corrupted label checksums.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Fedor Uporov <fuporov.vstack@gmail.com>
Closes #2509
Closes #12685

tests/runfiles/common.run

@@ -122,8 +122,9 @@ tags = ['functional', 'clean_mirror']
 tests = ['zdb_002_pos', 'zdb_003_pos', 'zdb_004_pos', 'zdb_005_pos',
     'zdb_006_pos', 'zdb_args_neg', 'zdb_args_pos',
     'zdb_block_size_histogram', 'zdb_checksum', 'zdb_decompress',
-    'zdb_display_block', 'zdb_object_range_neg', 'zdb_object_range_pos',
-    'zdb_objset_id', 'zdb_decompress_zstd', 'zdb_recover', 'zdb_recover_2']
+    'zdb_display_block', 'zdb_label_checksum', 'zdb_object_range_neg',
+    'zdb_object_range_pos', 'zdb_objset_id', 'zdb_decompress_zstd',
+    'zdb_recover', 'zdb_recover_2']
 pre =
 post =
 tags = ['functional', 'cli_root', 'zdb']

tests/zfs-tests/include/blkdev.shlib

@@ -652,3 +652,16 @@ function corrupt_blocks_at_level # input_file corrupt_level
 	# This is necessary for pools made of loop devices.
 	sync
 }
+
+function corrupt_label_checksum # label_number vdev_path
+{
+	typeset label_size=$((256*1024))
+	typeset vdev_size=$(stat_size ${2})
+	typeset -a offsets=("$((128*1024 - 32))" \
+	    "$(($label_size + (128*1024 - 32)))" \
+	    "$(($vdev_size - $label_size - (128*1024 + 32)))" \
+	    "$(($vdev_size - (128*1024 + 32)))")
+
+	dd if=/dev/urandom of=${2} seek=${offsets[$1]} bs=1 count=32 \
+	    conv=notrunc
+}

tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am

@@ -14,6 +14,7 @@ dist_pkgdata_SCRIPTS = \
 	zdb_object_range_neg.ksh \
 	zdb_object_range_pos.ksh \
 	zdb_display_block.ksh \
+	zdb_label_checksum.ksh \
 	zdb_objset_id.ksh \
 	zdb_recover.ksh \
 	zdb_recover_2.ksh

tests/zfs-tests/tests/functional/cli_root/zdb/zdb_label_checksum.ksh

@@ -0,0 +1,78 @@
+#!/bin/ksh
+
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2021 by vStack. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/include/blkdev.shlib
+
+#
+# Description:
+# zdb -l will report corrupted labels checksums
+#
+# Strategy:
+# 1. Create pool with some number of vdevs and export it
+# 2. Corrupt label 0 and label 1, check that corrupted labels are reported
+# 3. Check that pool still be imported correctly
+# 4. Corrupt all labels, check that all corrupted labels are reported
+# 5. Check that pool cannot be imported
+#
+
+log_assert "Verify zdb -l will report corrupted labels checksums"
+log_onexit cleanup
+
+VIRTUAL_DISK=$TEST_BASE_DIR/disk
+
+function cleanup
+{
+	poolexists $TESTPOOL && log_must destroy_pool $TESTPOOL
+	[[ -f $VIRTUAL_DISK ]] && log_must rm $VIRTUAL_DISK
+}
+
+verify_runnable "global"
+
+log_must truncate -s $(($MINVDEVSIZE * 8)) $VIRTUAL_DISK
+
+log_must zpool create $TESTPOOL $VIRTUAL_DISK
+log_must zpool export $TESTPOOL
+
+corrupt_label_checksum 0 $VIRTUAL_DISK
+corrupt_label_checksum 1 $VIRTUAL_DISK
+
+msg_count=$(zdb -l $VIRTUAL_DISK | grep -c '(Bad label cksum)')
+[ $msg_count -ne 1 ] && \
+    log_fail "zdb -l produces an incorrect number of corrupted labels."
+
+msg_count=$(zdb -lll $VIRTUAL_DISK | grep -c '(Bad label cksum)')
+[ $msg_count -ne 2 ] && \
+    log_fail "zdb -l produces an incorrect number of corrupted labels."
+
+log_must zpool import $TESTPOOL -d $TEST_BASE_DIR
+log_must zpool export $TESTPOOL
+
+corrupt_label_checksum 0 $VIRTUAL_DISK
+corrupt_label_checksum 1 $VIRTUAL_DISK
+corrupt_label_checksum 2 $VIRTUAL_DISK
+corrupt_label_checksum 3 $VIRTUAL_DISK
+
+msg_count=$(zdb -lll $VIRTUAL_DISK | grep -c '(Bad label cksum)')
+[ $msg_count -ne 4 ] && \
+    log_fail "zdb -l produces an incorrect number of corrupted labels."
+
+log_mustnot zpool import $TESTPOOL -d $TEST_BASE_DIR
+
+cleanup
+
+log_pass "zdb -l bad cksum report is correct."