zdb -k does not work on Linux when used with -e

This minor bug was introduced with the port of the feature from
OpenZFS to ZoL. This patch fixes the issue that was caused by
a minor re-ordering from the original code.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Closes #8001

cmd/zdb/zdb.c

@@ -6057,17 +6057,6 @@ main(int argc, char **argv)
 	error = 0;
 	target = argv[0];
 
-	char *checkpoint_pool = NULL;
-	char *checkpoint_target = NULL;
-	if (dump_opt['k']) {
-		checkpoint_pool = import_checkpointed_state(target, cfg,
-		    &checkpoint_target);
-
-		if (checkpoint_target != NULL)
-			target = checkpoint_target;
-
-	}
-
 	if (strpbrk(target, "/@") != NULL) {
 		size_t targetlen;
 
@@ -6113,6 +6102,24 @@ main(int argc, char **argv)
 		}
 	}
 
+	/*
+	 * import_checkpointed_state makes the assumption that the
+	 * target pool that we pass it is already part of the spa
+	 * namespace. Because of that we need to make sure to call
+	 * it always after the -e option has been processed, which
+	 * imports the pool to the namespace if it's not in the
+	 * cachefile.
+	 */
+	char *checkpoint_pool = NULL;
+	char *checkpoint_target = NULL;
+	if (dump_opt['k']) {
+		checkpoint_pool = import_checkpointed_state(target, cfg,
+		    &checkpoint_target);
+
+		if (checkpoint_target != NULL)
+			target = checkpoint_target;
+	}
+
 	if (target_pool != target)
 		free(target_pool);
 

tests/zfs-tests/tests/functional/pool_checkpoint/checkpoint_zdb.ksh

@@ -19,7 +19,7 @@
 
 #
 # DESCRIPTION:
-#	Ensure that checkpoint verification within zdb wowrks as
+#	Ensure that checkpoint verification within zdb works as
 #	we expect.
 #
 # STRATEGY:
@@ -30,10 +30,12 @@
 #	5. Verify zdb finds checkpoint when run on current state
 #	6. Verify zdb finds old dataset when run on checkpointed
 #	   state
-#	7. Discard checkpoint
-#	8. Verify zdb does not find the checkpoint anymore in the
+#	7. Export pool, and verify the same things with zdb to
+#	   test the -e option.
+#	8. Import pool and discard checkpoint
+#	9. Verify zdb does not find the checkpoint anymore in the
 #	   current state.
-#	9. Verify that zdb cannot find the checkpointed state
+#	10.Verify that zdb cannot find the checkpointed state
 #	   anymore when trying to open it for verification.
 #
 
@@ -68,6 +70,22 @@ zdb $TESTPOOL | grep "Dataset $FS1" && \
 zdb -k $TESTPOOL | grep "Dataset $CHECKPOINTED_FS1" || \
 	log_fail "zdb could not find destroyed dataset in checkpoint"
 
+log_must zpool export $TESTPOOL
+
+zdb -e $TESTPOOL | grep "Checkpointed uberblock found" || \
+	log_fail "zdb could not find checkpointed uberblock"
+
+zdb -k -e $TESTPOOL | grep "Checkpointed uberblock found" && \
+	log_fail "zdb found checkpointed uberblock in checkpointed state"
+
+zdb -e $TESTPOOL | grep "Dataset $FS1" && \
+	log_fail "zdb found destroyed dataset in current state"
+
+zdb -k -e $TESTPOOL | grep "Dataset $CHECKPOINTED_FS1" || \
+	log_fail "zdb could not find destroyed dataset in checkpoint"
+
+log_must zpool import $TESTPOOL
+
 log_must zpool checkpoint -d $TESTPOOL
 
 zdb $TESTPOOL | grep "Checkpointed uberblock found" && \

tests/zfs-tests/tests/functional/pool_checkpoint/pool_checkpoint.kshlib

@@ -161,7 +161,16 @@ function cleanup_nested_pool
 function cleanup_test_pool
 {
 	log_must zpool destroy $TESTPOOL
-	zpool labelclear -f "$TESTDISK"
+
+	#
+	# We always clear the labels of all disks
+	# between tests so imports from zpool or
+	# or zdb do not get confused with leftover
+	# data from old pools.
+	#
+	for disk in $DISKS; do
+		zpool labelclear -f $disk
+	done
 }
 
 function cleanup_nested_pools