Fix intra-pool resumable 'zfs send -t <token>'

Because resuming from a token requires "guid" -> "snapshot" mapping
we have to walk the whole dataset hierarchy to find the right snapshot
to send; when both source and destination exists, for an incremental
resumable stream, libzfs gets confused and picks up the wrong snapshot
to send from: this results in attempting to send

   "destination@snap1 -> source@snap2"

instead of

   "source@snap1 -> source@snap2"

which fails with a "Invalid cross-device link" error (EXDEV).

Fix this by adjusting the logic behind dataset traversal in
zfs_iter_children() to pick the right snapshot to send from.

Additionally update dry-run 'zfs send -t' to print its output to
stderr: this is consistent with other dry-run commands.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #6618
Closes #6619
Closes #6623

lib/libzfs/libzfs_iter.c

@@ -428,10 +428,10 @@ zfs_iter_children(zfs_handle_t *zhp, zfs_iter_f func, void *data)
 {
 	int ret;
 
-	if ((ret = zfs_iter_filesystems(zhp, func, data)) != 0)
+	if ((ret = zfs_iter_snapshots(zhp, B_FALSE, func, data)) != 0)
 		return (ret);
 
-	return (zfs_iter_snapshots(zhp, B_FALSE, func, data));
+	return (zfs_iter_filesystems(zhp, func, data));
 }
 
 

lib/libzfs/libzfs_sendrecv.c

@@ -1654,6 +1654,7 @@ zfs_send_resume(libzfs_handle_t *hdl, sendflags_t *flags, int outfd,
 	int error = 0;
 	char name[ZFS_MAX_DATASET_NAME_LEN];
 	enum lzc_send_flags lzc_flags = 0;
+	FILE *fout = (flags->verbose && flags->dryrun) ? stdout : stderr;
 
 	(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
 	    "cannot resume send"));
@@ -1668,9 +1669,9 @@ zfs_send_resume(libzfs_handle_t *hdl, sendflags_t *flags, int outfd,
 		return (zfs_error(hdl, EZFS_FAULT, errbuf));
 	}
 	if (flags->verbose) {
-		(void) fprintf(stderr, dgettext(TEXT_DOMAIN,
+		(void) fprintf(fout, dgettext(TEXT_DOMAIN,
 		    "resume token contents:\n"));
-		nvlist_print(stderr, resume_nvl);
+		nvlist_print(fout, resume_nvl);
 	}
 
 	if (nvlist_lookup_string(resume_nvl, "toname", &toname) != 0 ||
@@ -1729,7 +1730,7 @@ zfs_send_resume(libzfs_handle_t *hdl, sendflags_t *flags, int outfd,
 		    lzc_flags, &size);
 		if (error == 0)
 			size = MAX(0, (int64_t)(size - bytes));
-		send_print_verbose(stderr, zhp->zfs_name, fromname,
+		send_print_verbose(fout, zhp->zfs_name, fromname,
 		    size, flags->parsable);
 	}
 

tests/zfs-tests/tests/functional/rsend/rsend.kshlib

@@ -505,11 +505,13 @@ function test_fs_setup
 {
 	typeset sendfs=$1
 	typeset recvfs=$2
+	typeset streamfs=$3
 	typeset sendpool=${sendfs%%/*}
 	typeset recvpool=${recvfs%%/*}
 
 	datasetexists $sendfs && log_must_busy zfs destroy -r $sendpool
 	datasetexists $recvfs && log_must_busy zfs destroy -r $recvpool
+	datasetexists $streamfs && log_must_busy zfs destroy -r $streamfs
 
 	if $(datasetexists $sendfs || zfs create -o compress=lz4 $sendfs); then
 		mk_files 1000 256 0 $sendfs &
@@ -538,10 +540,7 @@ function test_fs_setup
 		    ">/$sendpool/incremental.zsend"
 	fi
 
-	if datasetexists $streamfs; then
-		log_must_busy zfs destroy -r $streamfs
-	fi
-	log_must zfs create -o compress=lz4 $sendpool/stream
+	log_must zfs create -o compress=lz4 $streamfs
 }
 
 #
@@ -655,9 +654,10 @@ function resume_cleanup
 {
 	typeset sendfs=$1
 	typeset streamfs=$2
+	typeset sendpool=${sendfs%%/*}
 
 	datasetexists $sendfs && log_must_busy zfs destroy -r $sendfs
 	datasetexists $streamfs && log_must_busy zfs destroy -r $streamfs
 	cleanup_pool $POOL2
-	rm -f /$POOL/initial.zsend /$POOL/incremental.zsend
+	rm -f /$sendpool/initial.zsend /$sendpool/incremental.zsend
 }

tests/zfs-tests/tests/functional/rsend/rsend_019_pos.ksh

@@ -48,8 +48,8 @@ sendfs=$POOL/sendfs
 recvfs=$POOL3/recvfs
 streamfs=$POOL2/stream
 
-for sendfs in $POOL2/sendfs $POOL2; do
-	test_fs_setup $sendfs $recvfs
+for sendfs in $POOL2/sendfs $POOL3; do
+	test_fs_setup $sendfs $recvfs $streamfs
 	resume_test "zfs send -v $sendfs@a" $streamfs $recvfs
 	resume_test "zfs send -v -i @a $sendfs@b" $streamfs $recvfs
 	file_check $sendfs $recvfs

tests/zfs-tests/tests/functional/rsend/rsend_020_pos.ksh

@@ -47,7 +47,7 @@ streamfs=$POOL/stream
 
 log_onexit resume_cleanup $sendfs $streamfs
 
-test_fs_setup $sendfs $recvfs
+test_fs_setup $sendfs $recvfs $streamfs
 resume_test "zfs send -D -v $sendfs@a" $streamfs $recvfs
 file_check $sendfs $recvfs
 

tests/zfs-tests/tests/functional/rsend/rsend_021_pos.ksh

@@ -49,7 +49,7 @@ streamfs=$POOL/stream
 
 log_onexit resume_cleanup $sendfs $streamfs
 
-test_fs_setup $sendfs $recvfs
+test_fs_setup $sendfs $recvfs $streamfs
 resume_test "zfs send -v -e $sendfs@a" $streamfs $recvfs
 resume_test "zfs send -v -e -i @a $sendfs@b" $streamfs $recvfs
 file_check $sendfs $recvfs

tests/zfs-tests/tests/functional/rsend/rsend_022_pos.ksh

@@ -52,7 +52,7 @@ streamfs=$POOL/stream
 
 log_onexit resume_cleanup $sendfs $streamfs
 
-test_fs_setup $sendfs $recvfs
+test_fs_setup $sendfs $recvfs $streamfs
 log_must zfs bookmark $sendfs@a $sendfs#bm_a
 log_must_busy zfs destroy $sendfs@a
 log_must zfs receive -v $recvfs </$POOL/initial.zsend

tests/zfs-tests/tests/functional/rsend/rsend_024_pos.ksh

@@ -49,7 +49,7 @@ streamfs=$POOL/stream
 
 log_onexit resume_cleanup $sendfs $streamfs
 
-test_fs_setup $sendfs $recvfs
+test_fs_setup $sendfs $recvfs $streamfs
 log_must zfs unmount -f $sendfs
 resume_test "zfs send $sendfs" $streamfs $recvfs
 file_check $sendfs $recvfs

tests/zfs-tests/tests/functional/rsend/send-c_resume.ksh

@@ -41,7 +41,7 @@ streamfs=$POOL/stream
 log_assert "Verify compressed send streams can be resumed if interrupted"
 log_onexit resume_cleanup $sendfs $streamfs
 
-test_fs_setup $sendfs $recvfs
+test_fs_setup $sendfs $recvfs $streamfs
 resume_test "zfs send -c -v $sendfs@a" $streamfs $recvfs
 resume_test "zfs send -c -v -i @a $sendfs@b" $streamfs $recvfs
 file_check $sendfs $recvfs