zpool import cachefile improvements

Importing a pool using the cachefile is ideal to reduce the time
required to import a pool. However, if the devices associated with
a pool in the cachefile have changed, then the import would fail.
This can easily be corrected by doing a normal import which would
then read the pool configuration from the labels.

The goal of this change is make importing using a cachefile more
resilient and auto-correcting. This is accomplished by having
the cachefile import logic automatically fallback to reading the
labels of the devices similar to a normal import. The main difference
between the fallback logic and a normal import is that the cachefile
import logic will only look at the device directories that were
originally used when the cachefile was populated. Additionally,
the fallback logic will always import by guid to ensure that only
the pools in the cachefile would be imported.

External-issue: DLPX-71980
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Wilson <gwilson@delphix.com>
Closes #11716

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

@@ -9,6 +9,7 @@ dist_pkgdata_SCRIPTS = \
 	import_cachefile_device_replaced.ksh \
 	import_cachefile_mirror_attached.ksh \
 	import_cachefile_mirror_detached.ksh \
+	import_cachefile_paths_changed.ksh \
 	import_cachefile_shared_device.ksh \
 	import_devices_missing.ksh \
 	import_paths_changed.ksh \

tests/zfs-tests/tests/functional/cli_root/zpool_import/import_cachefile_paths_changed.ksh

@@ -0,0 +1,117 @@
+#!/bin/ksh -p
+
+#
+# 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 Delphix. All rights reserved.
+#
+
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.kshlib
+
+#
+# DESCRIPTION:
+#	A pool should be importable from a cachefile even if device paths
+#	have changed.
+#
+# STRATEGY:
+#	1. Create a pool using a cachefile
+#	2. Backup cachefile
+#	3. Export the pool.
+#	4. Change the paths of some of the devices.
+#	5. Verify that we can import the pool using the cachefile.
+#
+
+verify_runnable "global"
+
+log_onexit cleanup
+
+function test_new_paths
+{
+	typeset poolcreate="$1"
+	typeset pathstochange="$2"
+
+	log_note "$0: pool '$poolcreate', changing paths of $pathstochange."
+
+	log_must zpool create -o cachefile=$CPATH $TESTPOOL1 $poolcreate
+
+	log_must cp $CPATH $CPATHBKP
+
+	log_must zpool export $TESTPOOL1
+
+	for dev in $pathstochange; do
+		log_must mv $dev "${dev}_new"
+	done
+
+	log_must zpool import -c $CPATHBKP $TESTPOOL1
+	log_must check_pool_healthy $TESTPOOL1
+
+	# Cleanup
+	log_must zpool destroy $TESTPOOL1
+	log_must rm -f $CPATH $CPATHBKP
+	for dev in $pathstochange; do
+		log_must mv "${dev}_new" $dev
+	done
+
+	log_note ""
+}
+
+function test_duplicate_pools
+{
+	typeset poolcreate="$1"
+	typeset pathstocopy="$2"
+
+	log_note "$0: pool '$poolcreate', creating duplicate pool using $pathstocopy."
+
+	log_must zpool create -o cachefile=$CPATH $TESTPOOL1 $poolcreate
+	log_must zpool export $TESTPOOL1
+
+	for dev in $pathstocopy; do
+		log_must cp $dev "${dev}_orig"
+
+	done
+
+	log_must zpool create -f -o cachefile=$CPATH $TESTPOOL1 $poolcreate
+	log_must cp $CPATH $CPATHBKP
+	log_must zpool export $TESTPOOL1
+
+	for dev in $pathstocopy; do
+		log_must mv $dev "${dev}_new"
+	done
+
+	log_must zpool import -c $CPATHBKP
+	log_must zpool import -c $CPATHBKP $TESTPOOL1
+	log_must check_pool_healthy $TESTPOOL1
+
+	# Cleanup
+	log_must zpool destroy $TESTPOOL1
+	log_must rm -f $CPATH $CPATHBKP
+	for dev in $pathstocopy; do
+		log_must rm "${dev}_orig"
+		log_must mv "${dev}_new" $dev
+	done
+
+	log_note ""
+}
+
+test_new_paths "$VDEV0 $VDEV1" "$VDEV0 $VDEV1"
+test_new_paths "mirror $VDEV0 $VDEV1" "$VDEV0 $VDEV1"
+test_new_paths "$VDEV0 log $VDEV1" "$VDEV0 $VDEV1"
+test_new_paths "raidz $VDEV0 $VDEV1 $VDEV2" "$VDEV0 $VDEV1 $VDEV2"
+test_new_paths "draid $VDEV0 $VDEV1 $VDEV2" "$VDEV0 $VDEV1 $VDEV2"
+
+test_duplicate_pools "$VDEV0 $VDEV1" "$VDEV0 $VDEV1"
+test_duplicate_pools "mirror $VDEV0 $VDEV1" "$VDEV0 $VDEV1"
+test_duplicate_pools "$VDEV0 log $VDEV1" "$VDEV0 $VDEV1"
+test_duplicate_pools "raidz $VDEV0 $VDEV1 $VDEV2" "$VDEV0 $VDEV1 $VDEV2"
+test_duplicate_pools "draid $VDEV0 $VDEV1 $VDEV2" "$VDEV0 $VDEV1 $VDEV2"
+
+log_pass "zpool import with cachefile succeeded after changing device paths."