Add zdb -r <dataset> <object-id | file> <output>

While you can use zdb -R poolname vdev:offset:[<lsize>/]<psize>[:flags] 
to extract individual DVAs from a vdev, it would be handy for be able 
copy an entire file out of the pool.

Given a file or object number, add support to copy the contents to a 
file. Useful for debugging and recovery.

Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Allan Jude <allan@klarasystems.com>
Closes #11027

tests/runfiles/common.run

@@ -119,7 +119,7 @@ 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_objset_id', 'zdb_decompress_zstd', 'zdb_recover', 'zdb_recover_2']
 pre =
 post =
 tags = ['functional', 'cli_root', 'zdb']

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

@@ -14,4 +14,6 @@ dist_pkgdata_SCRIPTS = \
 	zdb_object_range_neg.ksh \
 	zdb_object_range_pos.ksh \
 	zdb_display_block.ksh \
-	zdb_objset_id.ksh
+	zdb_objset_id.ksh \
+	zdb_recover.ksh \
+	zdb_recover_2.ksh

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

@@ -56,7 +56,7 @@ set -A args "create" "add" "destroy" "import fakepool" \
     "add mirror fakepool" "add raidz fakepool" \
     "add raidz1 fakepool" "add raidz2 fakepool" \
     "setvprop" "blah blah" "-%" "--?" "-*" "-=" \
-    "-a" "-f" "-g" "-j" "-n" "-o" "-p" "-p /tmp" "-r" \
+    "-a" "-f" "-g" "-j" "-n" "-o" "-p" "-p /tmp" \
     "-t" "-w" "-z" "-E" "-H" "-I" "-J" "-K" \
     "-N" "-Q" "-R" "-T" "-W"
 

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

@@ -0,0 +1,55 @@
+#!/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 Allan Jude.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# Description:
+# zdb -r <dataset> <path> <destination>
+# Will extract <path> (relative to <dataset>) to the file <destination>
+# Similar to -R, except it does the work for you to find each record
+#
+# Strategy:
+# 1. Create a pool
+# 2. Write some data to a file
+# 3. Extract the file
+# 4. Compare the file to the original
+#
+
+function cleanup
+{
+	datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+	rm $tmpfile
+}
+
+log_assert "Verify zdb -r <dataset> <path> <dest> extract the correct data."
+log_onexit cleanup
+init_data=$TESTDIR/file1
+tmpfile="$TEST_BASE_DIR/zdb-recover"
+write_count=8
+blksize=131072
+verify_runnable "global"
+verify_disk_count "$DISKS" 2
+
+default_mirror_setup_noexit $DISKS
+file_write -o create -w -f $init_data -b $blksize -c $write_count
+log_must zpool sync $TESTPOOL
+
+output=$(zdb -r $TESTPOOL/$TESTFS file1 $tmpfile)
+log_must cmp $init_data $tmpfile
+
+log_pass "zdb -r <dataset> <path> <dest> extracts the correct data."

tests/zfs-tests/tests/functional/cli_root/zdb/zdb_recover_2.ksh

@@ -0,0 +1,57 @@
+#!/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 Allan Jude.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# Description:
+# zdb -r <dataset> <path> <destination>
+# Will extract <path> (relative to <dataset>) to the file <destination>
+# Similar to -R, except it does the work for you to find each record
+#
+# Strategy:
+# 1. Create a pool
+# 2. Write some data to a file
+# 3. Append to the file so it isn't an divisible by 2
+# 4. Extract the file
+# 5. Compare the file to the original
+#
+
+function cleanup
+{
+	datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+	rm $tmpfile
+}
+
+log_assert "Verify zdb -r <dataset> <path> <dest> extract the correct data."
+log_onexit cleanup
+init_data=$TESTDIR/file1
+tmpfile="$TEST_BASE_DIR/zdb-recover"
+write_count=8
+blksize=131072
+verify_runnable "global"
+verify_disk_count "$DISKS" 2
+
+default_mirror_setup_noexit $DISKS
+file_write -o create -w -f $init_data -b $blksize -c $write_count
+log_must echo "zfs" >> $init_data
+log_must zpool sync $TESTPOOL
+
+output=$(zdb -r $TESTPOOL/$TESTFS file1 $tmpfile)
+log_must cmp $init_data $tmpfile
+
+log_pass "zdb -r <dataset> <path> <dest> extracts the correct data."